Test Bank for Gordis Epidemiology 6th Edition by David Celentano & Moyses Szklo

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TEST BANK

2023

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COMPLETE Elaborated Test Bank for Gordis Epidemiology 6th Edition David D Celentano Moyses Szklo 2023

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Gordis Epidemiology 6th Edition by David D Celentano & Moyses Szklo

ISBN-10 0323552293 ISBN-13 978-0275972165 Test bank for Gordis Epidemiology 6th Edition by David D Celentano & Moyses Szklo

ISBN-10 0323552293 ISBN-13 978-0275972165

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TABLE OF CONTENTS Chapter 1: Introduction

Chapter 2: The Dynamics of Disease Transmission Chapter 3: The Occurrence of Disease: I. Disease Surveillance and Measures of Morbidity Chapter 4: The Occurrence of Disease: II. Mortality and Other Measures of Disease Impact Chapter 5: Assessing the Validity and Reliability of Diagnostic and Screening Tests Chapter 6: The Natural History of Disease: Ways of Expressing Prognosis Chapter 7: Observational Studies Chapter 8: Cohort Studies Chapter 9: Comparing Cohort and Case-Control Studies Chapter 10: Assessing Preventive and Therapeutic Measures: Randomized Trials Chapter 11: Randomized Trials: Some Further Issues Chapter 12: Estimating Risk: Is There an Association?

Chapter 13: More on Risk: Estimating the Potential for Prevention Chapter 14: From Association to Causation: Deriving Inferences From Epidemiologic Studies Chapter 15: More on Causal Inference: Bias, Confounding, and Interaction Chapter 16: Identifying the Roles of Genetic and Environmental Factors in Disease Causation Chapter 17: Using Epidemiology to Evaluate Health Services Chapter 18: Epidemiologic Approach to Evaluating Screening Programs Chapter 19: Epidemiology and Public Policy Chapter 20: Ethical and Professional Issues in Epidemiology

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Chapter 01: Introduction Celentano: Gordis Epidemiology, 6th Edition Test Bank MULTIPLE CHOICE 1. Which of the following is an example of tertiary prevention? a. Vaccination for rotavirus for children younger than the age of 1 year b. Surgical amputation of an extremity with osteosarcoma (bone cancer) c. Screening for gestational diabetes after 24 weeks of pregnancy d. Sexual education program in elementary schools e. Increasing taxes for buying cigarettes ANS: B Surgical amputation of an extremity with osteosarcoma (bone cancer) is an example in which when a disease is present the treatment (amputation) is done to reduce the impact of disease by preventing the tumor from dissemination. Vaccination for rotavirus for children younger than the age of 1 year, sexual education program in elementary schools, and increasing taxes for buying cigarettes represent examples of primary prevention. Screening for gestational diabetes after 24 weeks of pregnancy is an example of secondary prevention.

2. This historic character observed that childbed fever mortality was more common among women treated by physicians and medical students compared with women treated by midwives. Based on his observations, he implemented a hand wash policy that resulted in a decrease in mortality. Name the character that we are talking about. a. John Snow b. Edward Jenner c. D.A. Henderson d. Leon Gordis e. Ignaz Semmelweis ANS: E Ignaz Semmelweis identified that medical students and physicians transmitted the disease by not washing their hands after examining bodies at autopsies and conducting multiple examinations in the clinic.

3. Thanks to the contributions of Edward Jenner, the following disease was eradicated later by efforts organized by D.A. Henderson: a. Cholera b. Smallpox c. Chickenpox d. Polio e. Zika

Copyright © 2020 by Elsevier, Inc. All rights reserved.

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ANS: B Smallpox was eradicated in 1980. Edward Jenner vaccinated James Phipps in 1796 against smallpox. Almost 200 years later, the World Health Organization (WHO) commissioned D.A. Henderson to lead the efforts to eradicate the disease.

4. Over the past century, a marked decline in the mortality rates of many infectious diseases has been observed. Which of the following is the most likely reason for the observed decline in mortality rates from common infectious diseases? a. Development of penicillin b. Development of insulin c. Development of vaccines d. Improvement in social conditions e. Worse sanitation and unsafe water ANS: D Although medical treatments potentially helped in the decrease of infectious diseases, the advancement in social conditions played a major role. These improvements include better sanitation, safe disposal of waste, better nutrition, and improvement in housing conditions.

Copyright © 2020 by Elsevier, Inc. All rights reserved.

Chapter 02: The Dynamics of Disease Transmission Celentano: Gordis Epidemiology, 6th Edition Test Bank MULTIPLE CHOICE 1. Which term most accurately describes the following definition? “The occurrence in a community or region of cases of an illness, specific health-related behavior, or other healthrelated events clearly in excess of normal expectancy.” [Porta M, ed. A Dictionary of Epidemiology. New York: Oxford University Press; 2014.] a. Endemic b. Epidemic c. Pandemic d. Attack rate e. Incubation period ANS: B An epidemic is the occurrence of health-related events in a community or region, in clear excess of normal expectation. Endemic is not true because it is defined as the constant occurrence of a disease, disorder, or noxious infectious agent in a geographic area or population group. Pandemic is not true because it is defined as an epidemic occurring over a very wide area, crossing international boundaries, and usually affecting a large number of people. Attack rate is not true because it is defined as number of people at risk in whom a certain illness develops over total number of people at risk. Incubation period is not true because it is the interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms).

2. What is the most accurate definition of the incubation period (of an infectious disease)? a. The time of onset of clinical illness or the onset of recognizable symptoms b. The interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms) c. The time of invasion by an infectious agent d. The time between initiation of infection and first shedding or excretion of the agent e. The period between exposure and the onset of infectiousness ANS: B The incubation period is defined as the interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms); in other words, the time between the moment of developing symptoms and the moment of invasion by an infectious agent. “The time of onset of clinical illness or the onset of recognizable symptoms” is not true as it corresponds to “time of onset.” “The time of invasion by an infectious agent” is not true as it corresponds to “time of infection.” “The time between initiation of infection and first shedding or excretion of the agent” and “The period between exposure and the onset of infectiousness” are not true as they correspond to the latent period. (The latent period is

Copyright © 2020 by Elsevier, Inc. All rights reserved.

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focusing on the onset of infectiousness, but the incubation period is focusing on the onset of the symptom.)

3. There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference.

Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. Based only on the information given in this question, how many people are at risk in this food poisoning outbreak? a. 1,000 b. 1,100 c. 1,150 d. 150 e. 50 ANS: B People at risk in this outbreak are people who were exposed to the food at the conference.

Even though 1,150 people were at the conference, 50 people who served the food did not eat the food. Therefore we have to exclude those 50 people.

4. There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference.

Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. After an initial outbreak of food poisoning is reported, an epidemiologist sends surveys to all people at risk to investigate the cause. However, only 900 people among those at risk answer the survey. After analysis of 900 survey results, the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti. What is the overall attack rate for those who ate meatball spaghetti? Use the following table to answer the question.

Summary of Survey Responses Number of people who developed the case definition symptoms

Number of people who ate the food

Pepperoni pizza only

113

275

Meatball spaghetti only

62

375

Both pepperoni pizza and meatball spaghetti

57

150

Neither of pepperoni pizza or meatball spaghetti

10

100

a. 41% b. 38% c. 27%

Copyright © 2020 by Elsevier, Inc. All rights reserved.

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d. 40% e. 23% ANS: E To calculate the food-specific attack rate, we need to define how many people are exposed to the specific food and how many people develop the symptoms in the case definition. In this question, we are asking about “overall” attack rate in those people who ate meatball spaghetti, so we have to add “meatball spaghetti only” and “both pepperoni pizza and meatball spaghetti” to get the overall rate. Which is 525 (375 plus 150), who are at risk of exposure, and 119 (62 plus 57), who developed the symptoms, corresponding to 23% of attack rate.

5. There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference.

Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. After an initial outbreak of food poisoning is reported, an epidemiologist sends surveys to all people at risk to investigate the cause. However, only 900 people among those at risk answer the survey. After analysis of 900 survey results, the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti. What is the most suspected food for food poisoning after cross-tabulation? Use the following table to answer the question.

Summary of Survey Responses Number of people who developed the case definition symptoms

Number of people who ate the food

Pepperoni pizza only

113

275

Meatball spaghetti only

62

375

Both pepperoni pizza and meatball spaghetti

57

150

Neither of pepperoni pizza or meatball spaghetti

10

100

a. Pepperoni pizza only b. Meatball spaghetti only c. Both pepperoni pizza and meatball spaghetti d. Neither pepperoni pizza nor meatball spaghetti e. We cannot determine the cause of food based on this information ANS: A Pepperoni pizza only attack rate is 41.09% (113 divided by 275), and meatball spaghetti only is 16.53% (62 divided by 375). The attack rate of both pepperoni pizza and meatball spaghetti is 38.00% (57 divided by 150). Some may choose both of them which are the most suspected

Copyright © 2020 by Elsevier, Inc. All rights reserved.

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food. If both the foods were the most suspected food, we should have a higher attack rate in meatball spaghetti only group as well.

6. What is the name of the occurrence of a clearly higher than expected number of cases of a disease within a limited geographical region? a. Pandemic b. Epidemic c. Endemic d. Zoonosis e. Attack rate ANS: B The definition of epidemic is precisely the occurrence of a clearly higher than habitual number of cases of a disease within a certain geographic region. Pandemic refers to a worldwide epidemic. Endemic refers to the habitual occurrence. Zoonosis describes a disease that is transmitted from animals to humans.

7. Malaria is a parasitic disease transmitted by the Anopheles mosquito bite. This mode of transmission is called a. direct. b. single exposure. c. multiple exposure. d. mosquitosis. e. vector.

ANS: E Diseases transmitted by mosquitos are called vector borne. Direct, single exposure, and multiple exposure represent other modes of transmission, and mosquitosis does not exist.

8. An outbreak of measles occurred in City A. There were 1,000 confirmed cases among children younger than 10 years old. Unfortunately, 50 children died of measles. Fifty represent 5% of the total number of cases. What concept is being illustrated in this example? a. Attack rate b. Secondary attack rate c. Case-fatality rate d. Incubation period e. Subclinical disease ANS: C Case-fatality rate is defined as the proportion of people who die of a disease, among the total number of cases of that disease. Attack rate and secondary attack rate refer to the proportion of people (at risk) who develop a disease among the total number of people who were at risk for the disease. Incubation period describes the period between the origin of disease and onset of clinical symptoms. Subclinical disease describes a disease that does not manifest clinically.

Copyright © 2020 by Elsevier, Inc. All rights reserved.

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9. During the conquest of Mexico, outbreaks played an important role that favored the Spaniards. There were several outbreaks of smallpox that killed thousands of natives.

Smallpox was introduced into America by the Europeans. Why were the natives particularly afflicted by smallpox outbreaks? a. Among natives, the proportion of susceptibles was higher. b. Among Spaniards, the proportion of immunes was extremely low. c. Spaniards had the cure for smallpox. d. Natives had a gene that made them more prone to die from smallpox. e. Spaniards were protected from smallpox because they had armors.

ANS: A Because natives were not introduced to the smallpox virus until after the Spaniards arrived, all of them were susceptibles. In a population with a higher proportion of susceptibles, outbreaks can initiate and spread easily. Spaniards had a better balance between susceptibles and immunes; therefore the likelihood of an outbreak happening among them was much lower.

10. The population of Oriol City in June 2018 was 612,437. According to the Oriol City’s health department, there were 329 new cases of Raven’s disease during 2018. Counting those new cases, by December 31 it was estimated that there were 6580 persons with Raven’s disease in Oriol City. What was the incidence rate of Raven’s disease in 2018? a. 26 per 100,000 population b. 33 per 100,000 population c. 54 per 100,000 population d. 1074 per 100,000 population e. 5000 per 100,000 population ANS: C The numerator to calculate the incidence rate is the total number of new cases (329), and the denominator is the total number of people who were at risk of developing the condition (in this case we use the population at the middle of that period, 612,437). We express the incidence rate per 100,000 to avoid the decimals: 329/612,437 = 0.000537  100,000 = 53.7.

11. The population of Oriol City in June 2018 was 612,437. According to the Oriol City’s health department, there were 329 new cases of Raven’s disease during 2018. Counting those new cases, by December 31 it was estimated that there were 6580 persons with Raven’s disease in Oriol City. What was the prevalence of Raven’s disease in 2018? a. 26 per 100,000 population b. 33 per 100,000 population c. 54 per 100,000 population d. 1074 per 100,000 population e. 5000 per 100,000 population ANS: D

Copyright © 2020 by Elsevier, Inc. All rights reserved.

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To calculate the prevalence of Raven’s disease, we use the total number of cases present at the end of the period (6580) divided by the total number of people in that city (612,437), thus: 6580/612,437 = 0.01074  100,000 = 1074.

Copyright © 2020 by Elsevier, Inc. All rights reserved.

lOMoARcPSD|8660651

ANS: B Smallpox was eradicated in 1980. Edward Jenner vaccinated James Phipps in 1796 against smallpox. Almost 200 years later, the World Health Organization (WHO) commissioned D.A. Henderson to lead the efforts to eradicate the disease.

4. Over the past century, a marked decline in the mortality rates of many infectious diseases has been observed. Which of the following is the most likely reason for the observed decline in mortality rates from common infectious diseases? a. Development of penicillin b. Development of insulin c. Development of vaccines d. Improvement in social conditions e. Worse sanitation and unsafe water ANS: D Although medical treatments potentially helped in the decrease of infectious diseases, the advancement in social conditions played a major role. These improvements include better sanitation, safe disposal of waste, better nutrition, and improvement in housing conditions.

lOMoARcPSD|8660651

Chapter 02: The Dynamics of Disease Transmission Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which term most accurately describes the following definition? “The occurrence in a community or region of cases of an illness, specific health-related behavior, or other healthrelated events clearly in excess of normal expectancy.” [Porta M, ed. A Dictionary of Epidemiology. New York: Oxford University Press; 2014.] a. Endemic b. Epidemic c. Pandemic d. Attack rate e. Incubation period ANS: B An epidemic is the occurrence of health-related events in a community or region, in clear excess of normal expectation. Endemic is not true because it is defined as the constant occurrence of a disease, disorder, or noxious infectious agent in a geographic area or population group. Pandemic is noN t truR e beIcauG se iB t i. s dCefined as an epidemic occurring over a U boundaries, S N T andOusually affecting a large number of very wide area, crossing international people. Attack rate is not true because it is defined as number of people at risk in whom a certain illness develops over total number of people at risk. Incubation period is not true because it is the interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms).

2. What is the most accurate definition of the incubation period (of an infectious disease)? a. The time of onset of clinical illness or the onset of recognizable symptoms b. The interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms) c. The time of invasion by an infectious agent d. The time between initiation of infection and first shedding or excretion of the agent e. The period between exposure and the onset of infectiousness ANS: B The incubation period is defined as the interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms); in other words, the time between the moment of developing symptoms and the moment of invasion by an infectious agent. “The time of onset of clinical illness or the onset of recognizable symptoms” is not true as it corresponds to “time of onset.” “The time of invasion by an infectious agent” is not true as it corresponds to “time of infection.” “The time between initiation of infection and first shedding or excretion of the agent” and “The period between exposure and the onset of infectiousness” are not true as they correspond to the latent period. (The latent period is

lOMoARcPSD|8660651

focusing on the onset of infectiousness, but the incubation period is focusing on the onset of the symptom.)

3. There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference.

Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. Based only on the information given in this question, how many people are at risk in this food poisoning outbreak? a. 1,000 b. 1,100 c. 1,150 d. 150 e. 50 ANS: B People at risk in this outbreak are people who were exposed to the food at the conference.

Even though 1,150 people were at the conference, 50 people who served the food did not eat the food. Therefore we have to exclude those 50 people.

4. There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference.

Except for 50 people who served N thU eR foS odI, N alG l oTf B th. eC paOrtM icipants and volunteers ate the food from the luncheon at the conference on April 1, 2018. After an initial outbreak of food poisoning is reported, an epidemiologist sends surveys to all people at risk to investigate the cause. However, only 900 people among those at risk answer the survey. After analysis of 900 survey results, the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti. What is the overall attack rate for those who ate meatball spaghetti? Use the following table to answer the question.

Summary of Survey Responses Number of people who ate the Number of people who developed the case definition food symptoms Pepperoni pizza only

113

275

Meatball spaghetti only

62

375

Both pepperoni pizza and meatball spaghetti

57

150

Neither of pepperoni pizza or meatball spaghetti

10

100

a. 41% b. 38% c. 27%

lOMoARcPSD|8660651

d. 40% e. 23% ANS: E To calculate the food-specific attack rate, we need to define how many people are exposed to the specific food and how many people develop the symptoms in the case definition. In this question, we are asking about “overall” attack rate in those people who ate meatball spaghetti, so we have to add “meatball spaghetti only” and “both pepperoni pizza and meatball spaghetti” to get the overall rate. Which is 525 (375 plus 150), who are at risk of exposure, and 119 (62 plus 57), who developed the symptoms, corresponding to 23% of attack rate.

5. There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference.

Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. After an initial outbreak of food poisoning is reported, an epidemiologist sends surveys to all people at risk to investigate the cause. However, only 900 people among those at risk answer the survey. After analysis of 900 survey results, the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti. What is the most suspected food for food poisoning after cross-tabulation? Use the following table to answer the question.

Summary of Survey Responses Nu peoB pl. eC whoM NUmRbSerIoNf G O developed theTcase definition

Number of people who ate the food

symptoms Pepperoni pizza only

113

275

Meatball spaghetti only

62

375

Both pepperoni pizza and meatball spaghetti

57

150

Neither of pepperoni pizza or meatball spaghetti

10

100

a. Pepperoni pizza only b. Meatball spaghetti only c. Both pepperoni pizza and meatball spaghetti d. Neither pepperoni pizza nor meatball spaghetti e. We cannot determine the cause of food based on this information ANS: A Pepperoni pizza only attack rate is 41.09% (113 divided by 275), and meatball spaghetti only is 16.53% (62 divided by 375). The attack rate of both pepperoni pizza and meatball spaghetti is 38.00% (57 divided by 150). Some may choose both of them which are the most suspected

lOMoARcPSD|8660651

food. If both the foods were the most suspected food, we should have a higher attack rate in meatball spaghetti only group as well.

6. What is the name of the occurrence of a clearly higher than expected number of cases of a disease within a limited geographical region? a. Pandemic b. Epidemic c. Endemic d. Zoonosis e. Attack rate ANS: B The definition of epidemic is precisely the occurrence of a clearly higher than habitual number of cases of a disease within a certain geographic region. Pandemic refers to a worldwide epidemic. Endemic refers to the habitual occurrence. Zoonosis describes a disease that is transmitted from animals to humans.

7. Malaria is a parasitic disease transmitted by the Anopheles mosquito bite. This mode of transmission is called a. direct. b. single exposure. c. multiple exposure. d. mosquitosis. e. vector.

ANS: E Diseases transmitted by mosquitos are called vector borne. Direct, single exposure, and multiple exposure represent other modes of transmission, and mosquitosis does not exist.

8. An outbreak of measles occurred in City A. There were 1,000 confirmed cases among children younger than 10 years old. Unfortunately, 50 children died of measles. Fifty represent 5% of the total number of cases. What concept is being illustrated in this example? a. Attack rate b. Secondary attack rate c. Case-fatality rate d. Incubation period e. Subclinical disease ANS: C Case-fatality rate is defined as the proportion of people who die of a disease, among the total number of cases of that disease. Attack rate and secondary attack rate refer to the proportion of people (at risk) who develop a disease among the total number of people who were at risk for the disease. Incubation period describes the period between the origin of disease and onset of clinical symptoms. Subclinical disease describes a disease that does not manifest clinically.

lOMoARcPSD|8660651

9. During the conquest of Mexico, outbreaks played an important role that favored the Spaniards. There were several outbreaks of smallpox that killed thousands of natives.

Smallpox was introduced into America by the Europeans. Why were the natives particularly afflicted by smallpox outbreaks? a. Among natives, the proportion of susceptibles was higher. b. Among Spaniards, the proportion of immunes was extremely low. c. Spaniards had the cure for smallpox. d. Natives had a gene that made them more prone to die from smallpox. e. Spaniards were protected from smallpox because they had armors.

ANS: A Because natives were not introduced to the smallpox virus until after the Spaniards arrived, all of them were susceptibles. In a population with a higher proportion of susceptibles, outbreaks can initiate and spread easily. Spaniards had a better balance between susceptibles and immunes; therefore the likelihood of an outbreak happening among them was much lower.

10. The population of Oriol City in June 2018 was 612,437. According to the Oriol City’s health department, there were 329 new cases of Raven’s disease during 2018. Counting those new cases, by December 31 it was estimated that there were 6580 persons with Raven’s disease in Oriol City. What was the incidence rate of Raven’s disease in 2018? a. 26 per 100,000 population b. 33 per 100,000 population c. 54 per 100,000 population d. 1074 per 100,000 population e. 5000 per 100,000 population ANS: C The numerator to calculate the incidence rate is the total number of new cases (329), and the denominator is the total number of people who were at risk of developing the condition (in this case we use the population at the middle of that period, 612,437). We express the incidence rate per 100,000 to avoid the decimals: 329/612,437 = 0.000537  100,000 = 53.7.

11. The population of Oriol City in June 2018 was 612,437. According to the Oriol City’s health department, there were 329 new cases of Raven’s disease during 2018. Counting those new cases, by December 31 it was estimated that there were 6580 persons with Raven’s disease in Oriol City. What was the prevalence of Raven’s disease in 2018? a. 26 per 100,000 population b. 33 per 100,000 population c. 54 per 100,000 population d. 1074 per 100,000 population e. 5000 per 100,000 population ANS: D

lOMoARcPSD|8660651

To calculate the prevalence of Raven’s disease, we use the total number of cases present at the end of the period (6580) divided by the total number of people in that city (612,437), thus: 6580/612,437 = 0.01074  100,000 = 1074.

lOMoARcPSD|8660651

Chapter 03: The Occurrence of Disease: I. Disease Surveillance and Measures of Morbidity Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which of the following statements is the most accurate definition? a. Active surveillance often gathers disease data from all potential reporting health care providers. b. Passive surveillance provides stimulus to health care providers in the form of individual feedback or other incentives. c. Sentinel surveillance is a type of surveillance based on selected population samples chosen to represent the relevant experience of particular groups. d. Active surveillance is continuous analysis, interpretation, and feedback of systematically collected data, generally using methods distinguished by their practicality, uniformity, and rapidity rather than by accuracy or completeness. e. Passive surveillance is an observational investigation, usually descriptive, in which information is systematically collected.

ANS: C

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Sentinel surveillance is a type of surveillance system. Instead of attempting to gather surveillance data from all health care providers, a sentinel surveillance system selects, either randomly or intentionally, a small group of healthproviders from whom to gather data.

“Active surveillance often gathers disease data from all potential reporting health care providers” is not correct. Active surveillance stimulus to health care providers in the form of individual feedback or other incentives. In active surveillance, providers contacted on regular basis to collect information. It is more resource intensive and mostly used for outbreak investigations or pilot studies. “Passive surveillance provides stimulus to health care providers in the form of individual feedback or other incentives” is not correct. Passive surveillance gathers disease data from all potential reporting health care providers. It is the most common type of surveillance. Providers are responsible for reporting. “Active surveillance is continuous analysis, interpretation, and feedback of systematically collected data, generally using methods distinguished by their practicality, uniformity, and rapidity rather than by accuracy or completeness” is not correct. This is one of the general definitions of surveillance. Surveillance is also defined a systematic and continuous collection, analysis, and interpretation of data, closely integrated with the timely and coherent dissemination of the results and assessment to those who have the right to know so that action can be taken.

“Passive surveillance is an observational investigation, usually descriptive, in which information is systematically collected” is not correct. A survey is an observational investigation, usually descriptive, in which information is systematically collected.

2. At an initial examination in Baltimore, Maryland, disease X was found in 10 of 1,000 men aged 40 to 50 years and in 10 of 2,000 women aged 30 to 40 years. Which of the following statement is the most accurate inference for the risk of developing disease X?

lOMoARcPSD|8660651

a. Men have a 2 times greater risk of developing disease X than women. b. Women have a 2 times greater risk of developing disease X than men. c. People aged between 40 and 50 years have a 2 times greater burden of developing disease X than people aged between 30 and 40. d. People aged between 30 and 40 years have a 2 times greater burden of developing disease X than people aged between 40 and 50. e. We cannot make any inference of risk of developing disease X. ANS: E The information provided in question is only prevalence of disease X at an initial examination. Based on information from prevalence, we cannot make any inference for risk of developing disease X. We should have newly diagnosed cases in a certain amount of time with population at risk for risk calculation and comparison. “Men have a 2 times greater risk of developing disease X than women,” “Women have a 2 times greater risk of developing disease X than men,” “People aged between 40 and 50 years have a 2 times greater burden of developing disease X than people aged between 30 and 40,” and “People aged between 30 and 40 years have a 2 times greater burden of developing disease X than people aged between 40 and 50” are not correct. Because we cannot perform a risk comparison based on disease prevalence. The accurate statement on disease prevalence is “Men aged 40 to 50 years have 2 times of greater prevalence of disease X than women aged 30 to 40 years.”

3. What is the incidence rate from influenza in the 2016 season in the young age group at Minas Tirith? Use the following table to answer the question.

Number of Residents, Diagnosed Cases, and Deaths From Influenza by Age No. of U S N TB.COM Age group No. of deaths from residents No. of diagnosed during 2016 season influenza during 2016 cases from influenza season during 2016 season Young

20,000

3,000

300

Old

10,000

1,000

500

a. 3,000 cases b. 150 cases/1,000 people c. 1,000 cases d. 100 cases/1,000 people e. 15 cases/1,000 people ANS: B Incidence rate equals number of diagnosed cases divided by number of people at risk. There are 3,000 diagnosed cases in the young age group, and its population is 20,000 people.

Therefore the incidence rate is 150 cases/1,000 people, which is 3,000 divided by 20,000.

“3,000 cases” is not correct; 3,000 cases is the number of diagnosed cases from influenza in the young age group. “1,000 cases” is not correct; 1,000 cases is the number of diagnosed cases from influenza in the old age group. “100 cases/1,000 people” is not correct; 100 cases/1,000 people is the incidence rate from influenza in the old age group. “15 cases/1,000 people” is not correct; 15 cases/1,000 people is the death rate from influenza in the young age group.

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4. In the student’s health clinic of a certain university, 140 cases of foot-hand-mouth disease were identified among the undergraduate students. This viral infection is usually mild, and none of the students got any complication. Because it is rare to observe this condition in people older than 10 years, the university reported their findings to the city’s health department. Three officers were sent to the university to interview and examine all the infected students and their contacts. By sending the three officers, what type of surveillance was implemented by the city health department in response to the university’s report? a. Sentinel b. Periodic c. Systematic d. Passive e. Active ANS: E When the health officers were asked to specifically go to the university and carry out the investigation, they started the active surveillance. Passive and sentinel surveillance were not used in this example because the city health department sent their personnel to carry out the surveillance rather than wait for the report of providers (students may argue that the university did report the outbreak; however, the question specifically asks about the deployment of health officers to the field). Periodic and systematic are not types of surveillance.

5. An epidemiologist decides to inN vU esR tigSaI teNthGeTinBc. idC enO ceMof diabetes in a population of 300 older adults who live in a nursing home. She visits the nursing home in January 1, 2017 and later in December 31 of the same year. She looks into the records of these patients and learns that in her first visit, 25 patients had diabetes and 35 in her second visit. What number should be in the numerator for her calculation of incidence? a. 10 b. 25 c. 35 d. 300 e. 275 ANS: A These 10 people represent the new cases of diabetes, because at the beginning there were already 25 diabetics. 300 represents the total population, and 275 represents the population at risk of diabetes at the beginning of the study.

6. An epidemiologist decides to investigate the incidence of diabetes in a population of 300 older adults who live in a nursing home. She visits the nursing home in January 1, 2017 and later in December 31 of the same year. She looks into the records of these patients and learns that in her first visit, 25 patients had diabetes and 35 in her second visit. What number should be included in the denominator for her calculation of incidence? a. 10

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b. 25 c. 35 d. 300 e. 275 ANS: E Because 25 patients already had diabetes at the beginning of her study, only 275 were at risk of diabetes. The denominator for calculating incidence should be the population at risk of getting the disease; therefore 275 is the right answer.

7. Suppose that the incidence of all types of cancer remains constant in a given country.

However, thanks to new treatments, the survival of cancer patients increases. What do you expect to happen to the prevalence of cancer in that country? a. Increase b. Decrease c. Remain constant d. Cannot be determined e. Duplicate ANS: A When the duration (survival) of a disease increases and the incidence remains constant, the prevalence will increase (remember that prevalence = incidence  duration).

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Chapter 04: The Occurrence of Disease: II. Mortality and Other Measures of Disease Impact Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. What is the attack rate (case-fatality rate) from influenza during the 2016 season in the young age group at Minas Tirith? Use the following table to answer the question.

Number of Residents, Diagnosed Cases, and Deaths From Influenza by Age Age group

No. of residents during 2016 season

No. of diagnosed cases from influenza during 2016 season

No. of deaths from influenza during 2016 season

Young

20,000

3,000

300

Old

10,000

1,000

500

a. 15% b. 5% c. 1.5% d. 10% e. 50% ANS: D Attack rate equals number of deaths divided by number of diagnosed cases. There are 300 deaths and 3,000 diagnosed cases in the young age group. The attack rate is 0.1 (10%), which is 300 divided by 3,000. 15% is not correct; 15% is the incidence rate from influenza in the young age group. However, percentage is a unit of incidence rate. 5% is not correct; 5% is the mortality rate from influenza in the old age group. However, percentage is a unit of mortality rate. 1.5% is not correct; 1.5% is the mortality rate from influenza in the young age group.

However, percentage is a unit of mortality rate. 50% is not correct; 50% is the attack rate from influenza in the old age group.

2. What is the mortality from influenza during the 2016 season in the old age group at Minas Tirith? Use the following table to answer the question.

Number of Residents, Diagnosed Cases, and Deaths From Influenza by Age Age group

No. of residents during 2016 season

No. of diagnosed cases from influenza during 2016 season

No. of deaths from influenza during 2016 season

Young

20,000

3,000

300

Old

10,000

1,000

500

a. 300 deaths

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b. 500 deaths c. 150 deaths/1,000 people d. 100 deaths/1,000 people e. 50 deaths/1,000 people ANS: E Mortality rate equals the number of deaths divided by the number of people at risk. There are 500 deaths in the young age group, and its population is 10,000 people. The mortality rate is 50 deaths/1,000 people. 300 deaths is not correct; 300 deaths is the number of deaths from influenza in the young age group. 500 deaths is not correct; 500 deaths is the number of deaths from influenza in the young age group. 150 deaths/1,000 people is not correct; 150 deaths/1,000 people is the incidence rate from influenza in the young age group with the wrong unit (incidence rate unit should be cases/people). 100 deaths/1,000 people is not correct; 100 deaths/1,000 people is the incidence rate from influenza in the old age group with the wrong unit (incidence rate unit should be cases/people).

3. For a disease such as seasonal influenza, which is less fatal and of short duration? a. Incidence rates and mortality rates will be similar. b. Mortality rates will be much higher than incidence rates. c. Incidence rates will be much higher than mortality rates. d. Incidence rates will be unrelated to mortality rates. e. None of the above.

ANS: C Due to the characteristics of the short duration of disease and low fatality, most of the newly diagnosed cases of influenza are recovered quickly. And only a few cases of deaths contribute to mortality rate. Therefore we normally have higher incidence rates from seasonal influenza compared with mortality rates from seasonal influenza.

4. What is the crude death rate from disease X for City A? Use the following table to answer the question.

Number of Residents and Deaths From Disease X by Age Group in City A and City B City A

City B

Age group

No. of residents

No. of deaths from disease X

No. of residents

No. of deaths from disease X

Age < 65

3,000

30

6,000

60

Age > 65

6,000

450

3,000

225

a. 53 deaths/1,000 people b. 32 deaths/1,000 people c. 10 deaths/1,000 people d. 75 deaths/1,000 people e. 43 deaths/1,000 people

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ANS: A Mortality rate equals number of deaths divided by number of people at risk. There are 480 deaths in City A, and its population is 9,000 people. The mortality rate is 53.3 deaths/1,000 people. 32 deaths/1,000 people is not correct; 32 deaths/1,000 people is the mortality rate from disease X in City B. 10 deaths/1,000 people is not correct; 10 deaths/1,000 people is the age-specific mortality rate of age younger than 65 from disease X in City A and City B. 75 deaths/1,000 people is not correct; 75 deaths/1,000 people is the age-specific mortality rate of age older than 65 from disease X in City A and City B. 43 deaths/1,000 people is not correct; 43 deaths/1,000 people is a crude mortality rate from disease X in City A and B (and also age-adjusted mortality rate from disease X in City A and City B).

5. What is the age-specific mortality rate from disease X in City B for age younger than 65?

Use the following table to answer the question.

Number of Residents and Deaths From Disease X by Age Group in City A and City B City A

City B

Age group

No. of residents

No. of deaths from disease X

No. of residents

No. of deaths from disease X

Age < 65

3,000

30

6,000

60

Age > 65

6,000

450

3,000

225

a. 53 deaths/1,000 people b. 32 deaths/1,000 people c. 10 deaths/1,000 people d. 75 deaths/1,000 people e. 43 deaths/1,000 people ANS: C The age-specific mortality rate of City B for age younger than 65 equals the number of deaths for age younger than 65 divided by the number of individuals at risk for age younger than 65.

There are 60 deaths for age younger than 65 in City A, and its population is 6,000 people for age younger than 65. The age-specific mortality rate of City B for age younger than 65 is 10 deaths/1,000 people.

6. Calculate the age-adjusted death rate from disease X in cities A and B by the direct method, using the total of both cities as the standard population. What is the age-adjusted death rate from disease X for City B? Use the following table to answer the question.

Number of Residents and Deaths From Disease X by Age Group in City A and City B City A

City B

Age group

No. of residents

No. of deaths from disease X

No. of residents

No. of deaths from disease X

Age < 65

3,000

30

6,000

60

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Age > 65

6,000

450

3,000

225

a. 53 deaths/1,000 people b. 32 deaths/1,000 people c. 10 deaths/1,000 people d. 75 deaths/1,000 people e. 43 deaths/1,000 people ANS: E The age-adjusted mortality rate of City B equals the sum of the expected number from agespecific strata divided by the overall standard population. The expected number for age younger than 65 equals the “age-specific mortality rate for age younger than 65” multiplied by the “age-specific standard population for age younger than 65,” which is 90 (60 divided by 6,000 multiplied by 9,000). The expected number for age greater than 65 equals the “agespecific mortality rate for age older than 65” multiplied by the “age-specific standard population for age older than 65,” which is 675 (225 divided by 3,000 multiplied by 9,000).

Therefore the age-adjusted mortality rate of City B is 43 deaths per 1,000 people (765 divided by 18,000). 53 deaths/1,000 people is not correct; 53 deaths/1,000 people is the mortality rate from disease X of City A. 32 deaths/1,000 people is not correct; 32 deaths/1,000 people is the mortality rate from disease X of City B. 10 deaths/1,000 people is not correct; 10 deaths/1,000 people is the age-specific mortality rate of age younger than 65 from disease X of City A and City B. 75 deaths/1,000 people is not correct; 75 deaths/1,000 people is the age-specific mortality rate of age older than 65 from disease X of City A and City B. 7. Which of the following statements is the most accurate interpretation of disease occurrence in City A and City B? Use the following table to answer the question.

Number of Residents and Deaths From Disease X by Age Group in City A and City B City A

City B

Age group

No. of residents

No. of deaths from disease X

No. of residents

No. of deaths from disease X

Age < 65

3,000

30

6,000

60

Age > 65

6,000

450

3,000

225

a. The age-adjusted mortality rate of City A is still higher than the mortality rate of City B, as compared with the crude mortality rate. b. The age-adjusted mortality rates for City A should be used to make decisions regarding allocation of funding for hospital care of the dying in City A. c. For direct age-adjustment, the weight for a given age category is the percentage of deaths for that age group. d. For direct age-adjustment, the weight for a given age category is the number of individuals in the standard population for that age group. e. The difference in the adjusted mortality rates between City A and City B is always attributable to differences in age composition between the two populations.

ANS: D

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For direct age-adjustment, we multiply the number in the standard population for that age group then divide by the total number of people in the standard population, which corresponds to the explanation “weight for a given age category is the number of individuals in the standard population for that age group”. “The age-adjusted mortality rate of City A is still higher than the mortality rate of City B, as compared with the crude mortality rate” is not correct. After direct age-adjustment, the mortality rate of City A is the same as the mortality rate of City B. “The age-adjusted mortality rates for City A should be used to make decisions regarding allocation of funding for hospital care of the dying in City A” is not correct. Crude mortality is the actual burden of disease, and crude mortality should be used for the decisionmaking process. “For direct age-adjustment, the weight for a given age category is the percentage of deaths for that age group” is not correct. See the previous answer. “The difference in the adjusted mortality rates between City A and City B is always attributable to differences in age composition between the two populations” is not correct. The difference in the adjusted mortality rates between City A and City B is attributable to differences in age composition between the two populations and differences in mortality rates between the two populations.

8. In 2016 there were 7,467 million people in the world. According to the World Health Organization, in the same year there were 56.9 million deaths worldwide; of those, 15.2 million were due to ischemic heart disease or stroke. What was the proportionate mortality of those two causes combined for that year? a. 0.8% b. 0.2% c. 3.7% d. 13.5% e. 26.7 % ANS: E The proportionate mortality represents the percentage of all deaths that are due to a specific cause (in this example, two causes combined). We calculate it using the following procedure: 56.9 million if the total number of deaths = 100% deaths. There were 15.2 million deaths due to ischemic heart disease or stroke; therefore 15.2 million represents 26.7% of all deaths.

Another way to express this number is 26.7% of all deaths were due to ischemic heart disease or stroke: (15.2  100)/56.9 = 26.7%.

9. According to the Centers of Disease Control and Prevention (CDC), during the Ebola outbreak of 2014 in West Africa, there were a total of 14,124 Ebola cases in Sierra Leone and 3,956 deaths due to Ebola. What was the case fatality rate in that country? a. 3.5% b. 22% c. 28% d. 3,956 e. 14,124 ANS: C

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3,956 deaths represent 28% of the total number of cases of Ebola. This proportion is known as the case-fatality rate.

10. A researcher finds that the standardized mortality rate (SMR) for epidemiologists compared with the general population is 100. What does that mean? a. The observed number of deaths for epidemiologists is the same as the expected. b. Epidemiologists have a mortality rate 100 times greater than the general population. c. Epidemiologists have a mortality rate 100 times lower than the general population. d. The general population experience a mortality rate increased as compared with epidemiologists. e. Nothing can be said with this information.

ANS: A SMR = 100 indicates that the observed number of deaths is the same as the expected.

11. The mayor of Baby City is interested in comparing the infant mortality rate (infants are defined as babies younger than the age of 12 months) of Baby City with the infant mortality rate of Adult City. He argues that the age distributions of these cities are very different and therefore asks you to calculate the age-adjusted infant mortality rate. What is the best approach? a. Use direct adjustment. b. Use indirect adjustment. c. Calculate the standardized mortN alU itR y rSaI tioN. d. Explain that no age adjustment is needed when comparing with age-specific mortality rates. e. Use the World Health Organization standard population to calculate an adjusted rate.

ANS: D Adjusted rates are calculated to compare the overall (all ages) mortality rates in two different places that have different age distributions. However, if age-specific mortality rates are to be compared, there is no need to adjust for age. In this example, infant mortality rates can be directly compared because both rates are age specific.

12. City A suffered some political changes and was divided into two cities named Alpha and Beta. Five years after the division, mortality rates in both cities are compared. The all-cause mortality rate in City Alpha is much higher than the rate in Beta. When looking at the demographic characteristics in the cities, you notice that the age distribution is almost exactly the same in both cities. What do you expect to find when the age-adjusted mortality rates are calculated and compared? a. City Alpha will have a much higher age-adjusted mortality rate than Beta. b. City Beta will have a much higher age-adjusted mortality rate than Alpha. c. The age-adjusted mortality rate will be much lower than the unadjusted rate in Alpha. d. The age-adjusted mortality rate will be much lower than the unadjusted rate in Beta. e. The answer cannot be determined without the actual numbers.

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ANS: A Because the age distribution in both cities is almost the same, we do not expect to see differences between the age-adjusted and the unadjusted mortality rates. Therefore, even after adjusting for age, Alpha will still have a much higher mortality rate than Beta.

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Chapter 05: Assessing the Validity and Reliability of Diagnostic and Screening Tests Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which of the following statements about specificity is the most accurate? a. The probability that a diseased person (case) in the population tested will be identified as diseased by the test. b. The probability that a person without the disease (noncase) in the population tested will be identified as nondiseased by the test. c. The probability that a person identified as diseased by the test will be a diseased person (case) in the population. d. The probability that a person identified as nondiseased by the test will be a person without the disease (noncase) in the population. e. The probability that a diseased person (case) in the population tested will be identified as nondiseased by the test.

ANS: B Specificity is the probability of coN rrecR tly I diagGnosB in. gC a person without the disease will be U test.

S NThe Tprobability identified as nondiseased status by the that a diseased person (case) in the population tested will be identified O “ as diseased by the test” corresponds to sensitivity, “The probability that a person identified as diseased by the test will be a diseased person (case) in the population” corresponds to the positive predictive value, “The probability that a person identified as nondiseased by the test will be a person without the disease (noncase) in the population” corresponds to the negative predictive value, and “The probability that a diseased person (case) in the population tested will be identified as nondiseased by the test” corresponds to false-positive.

2. A physical examination, digital rectal exam, was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men, all of whom showed no evidence of cancer at biopsy. The results of the physical examination were positive in 136 cases and in 165 control men. What is the sensitivity of the physical examination? a. 32% b. 47% c. 56% d. 57% e. Cannot calculate it based on given information ANS: B

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Sensitivity equals the “number of people who identified as diseased by the test” divided by the “number of people who actually have the disease.” The sensitivity is 0.47 (136 divided by 290).

3. A physical examination, digital rectal exam, was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men, all of whom showed no evidence of cancer at biopsy. The results of the physical examination were positive in 136 cases and in 165 control men. What is the specificity of the physical examination? a. 32% b. 47% c. 53% d. 68% e. Cannot calculate it based on given information ANS: D Specificity equals the “number of people who were identified as nondiseased by the test” divided by the “number of people who actually do not have the disease.” The specificity is 0.68 (351 divided by 516).

4. A physical examination, digital rectal exam, was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men, all of whom showed no evidence of cancer at biopsy. The results of the physical examination were positive in 136 cases and in 165 cN onU trR olSmIeN n.GNToB w. , tC heOhMealth commissioner in City A decides to use a physical exam, digital rectal exam, as a primary screening test for prostate cancer. What will be the positive predictive value of the physical examination? a. 45% b. 47% c. 68% d. 82% e. Cannot calculate it based on given information ANS: E To calculate the positive predictive value, we should have a prevalence of the disease in the population. However, in this question, we do not have any information on the prevalence of the disease. Therefore we cannot calculate the positive predictive value. Positive predictive value equals the “number of people who were identified as diseased by the test among who actually have the disease” divided by the “total number of people who were identified as diseased by the test.”

5. Which of the following statement about positive predictive value is the most accurate? a. Positive predictive value is a fixed characteristic of the test. It will not change over the person, place, and time. b. Positive predictive value is affected by the sensitivity of the test only. c. Specificity will not affect the positive predictive value.

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d. Positive predictive value is the probability that a diseased person (case) in the population tested will be identified as diseased by the test. e. None of above.

ANS: E Positive predictive value is the proportion of those who test positive who do have the disease or the probability that a person identified as diseased by the test will be a diseased person (case) in the population. “Positive predictive value is a fixed characteristic of the test. It will not change over the person, place, and time” is not correct, because positive predictive value is influenced by the prevalence of the disease. It is not a fixed characteristic of the test. It will change over the person, place, and time. “Positive predictive value is affected by the sensitivity of the test only” and “Specificity will not affect the positive predictive value” are not correct. Positive predictive value is affected by sensitivity, specificity, and prevalence.

“Positive predictive value is the probability that a diseased person (case) in the population tested will be identified as diseased by the test” is not correct as this is a definition of sensitivity.

6. Two physicians were asked to independently classify 250 ultrasounds as positive or negative. The comparison of their classification is shown in the following table. What is the simple percent agreement between the two physicians out of the total? Use the following table to answer the question.

Number of Positive and Negative Cases by Physician 1 and Physician 2 Physician 2

Physician 1

NURSINGTB.COM Positive

Negative

Positive

45

15

Negative

25

165

a. 24% b. 28% c. 53% d. 67% e. 84% ANS: E The simple percent agreement equals the “number of agreements” divided by the “total readings.” The simple percent agreement equals 0.84 (210 divided by 250).

7. Two infectious disease epidemiologists want to investigate a new laboratory test that identifies tuberculosis (TB) infections. Dr. Merritt uses the standard test, which has a sensitivity of 80% and a specificity of 90%. Dr. Foundry uses the new laboratory test, which is 90% sensitive and 99% specific. In City A, it is known that 100 of 1,000 people have TB infections. What is the positive predictive value of the standard test in City A? a. 10%

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b. 47% c. 53% d. 80% e. 90% ANS: B Positive predictive value is the proportion of those who test positive who do have the disease or the probability that a person identified as diseased by the test will be a diseased person (case) in the population. Let us say there are 10,000 people in City A; 100 of 1,000 people actually have TB infection in City A which is 1,000 individuals. Therefore we have 1,000 cases and 9,000 noncases in City A (hypothetically). The number of people who identified as test positive from cases is 800. Among 1,000 people who actually have TB, 80% of people will be identified as test positive (sensitivity). The number of people who identified as test positive from noncases is 900. Among 9,000 people who actually have TB, 90% of people will be identified as test negative (specificity) and 10% of people will be identified as test positive. Among 1,700 people who identified as test positive, there are 800 people who actually have the disease. Therefore positive predictive value equals 800 divided by 1,700 (equals 0.47).

8. Two infectious disease epidemiologists want to investigate a new laboratory test that identifies TB infections. Dr. Merritt uses the standard test, which has a sensitivity of 80% and a specificity of 90%. Dr. Foundry uses the new laboratory test, which is 90% sensitive and 99% specific. Now, epidemiologists decide to run those two test as sequential tests (two-stage testing). What is the effect on net sensitivity of sequential tests? a. 72% b. 80% c. 89% d. 90% e. 98% ANS: A In sequential screening tests, net sensitivity is a multiplicative value from each sensitivity value. Net sensitivity from sequential tests equals the sensitivity of test 1 multiplied by the sensitivity of test 2. The net sensitivity is 0.72 (0.8 multiplied by 0.9).

9. Mr. Patient tested positive for disease X. He went to see Dr. Gordis and asked him what was the probability of truly being sick given the results of the test. To answer that question, Dr. Gordis must know what about the test? a. Sensitivity b. Specificity c. Prevalence d. Positive predictive value e. Negative predictive value ANS: D

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The positive predictive value precisely represents the probability of having a disease given that the result from a test was positive. Sensitivity and specificity are the abilities of a test to recognize people with and without the disease, respectively. However, they do not provide information regarding the probability of having a disease given the result of the test. Negative predictive value represents the probability of not having a disease when the result of the test is negative.

10. A patient is weighed in the hospital by a nurse, and she is told she weighs 170 pounds.

The next morning she weighs herself at home, and her weight is 168 pounds. Assuming that both scales were calibrated and the patient was measured under the same circumstances (no shoes, light clothing). What can explain the difference in weight? a. Intrasubject variability b. Intersubject variability c. Intraobserver variability d. Low specificity of the test e. Low sensitivity of the test ANS: A Intrasubject variability refers to the changes that occur naturally over time in most variables measured for humans, such as weight, blood pressure, and blood glucose, among many others.

11. A 60-year-old patient was tested for Raven disease; his test came back negative.

However, he feels the test might bN eU wR roS nI gN anG dT wB an.tsCtO oM know what is the probability of not having Raven disease given that his test came back negative.

Test Disease (+) No disease (−) Total Positive (+) 84 44 128 36 836 872 Negative (−) Total 120 880 1,000 Using this table, answer to the following question: what proportion of the patients who tested negative are truly disease free? a. 4% b. 33% c. 66% d. 70% e. 96% ANS: E In other words, this question is asking, for the negative predictive value, “if a test result is negative, what is the probability that this patient does not have the disease?” The negative predictive value is calculated by dividing the number of true negatives (836 in this case) by the total number of negative tests (872 in this case); 836/872 = 0.958, or 96%.

12. A 60-year-old patient, who is an epidemiologist, was tested for Raven disease; his test came back positive. However, he is curious about the sensitivity of the test.

Test Disease (+) No disease (−) Total

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Positive (+) 84 44 128 Negative (−) 36 836 872 Total 120 880 1,000 Using this table, calculate the sensitivity of the test. a. 4% b. 33% c. 66% d. 70% e. 96% ANS: D The test’s sensitivity is calculated by dividing the number of true positives (84 in this case) by the total number of people with the disease (120 in this case); 84/120 = 0.70, or 70%.

13. A diagnostic test with a very high sensitivity but very low specificity has the following problem: a. It will miss a big proportion of true cases (label them as negatives). b. It will correctly identify all negative cases. c. It will label a big proportion of healthy people as sick (false-positives). d. It will be very expensive to administer. e. Specificity is the single most important characteristic of a test.

ANS: C A test with high sensitivity will be able to identify most of the cases. However, if its specificity is low, a big proportion of healthy people will be also labeled as positives (falsepositives).

14. The following are problems generated when a patient is given a false-positive diagnosis, except: a. Generate unnecessary expenses, as those labeled positive often go through other diagnostic procedures. b. Generates anxiety and worry. c. Increased burden to the healthcare system d. The opportunity for an effective intervention is missed. e. Unnecessary treatments are administered.

ANS: D “Generate unnecessary expenses, as those labeled positive often go through other diagnostic procedures,” “Generates anxiety and worry,” “Increased burden to the healthcare system,” “Unnecessary treatments are administered” represent problems that arise when a falsepositive diagnosis is given. “The opportunity for an effective intervention is missed” describes a problem that arises when a false-negative diagnosis is given.

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Chapter 06: The Natural History of Disease: Ways of Expressing Prognosis Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. What is the effective number exposed to risk of dying in the 13- to 24-month interval? Use the following table to answer the question.

Survival of Patients With Metastatic Cancer Z Following Diagnosis Interval since beginning treatment (months)

Alive at beginning of interval

Died Withdre during w during interva interval l

Effective number exposed to risk of dying

Proporti on who died during interval

Proportion who did not die during interval

Cumulative proportion who survived from enrollment to end of interval

x

Ix

dx

Wx

I’x

qx

px

Px

1–12

200

10

40

13–24

150

20

30

25–36

100

30

20

37–48

50

40

10

a. 40 b. 90 c. 120 d. 135 e. 160 ANS: D The effective number of exposed to risk of dying is defined as the “number of alive at beginning of interval” less “half of number withdrew during interval.” The effective number of exposed to risk of dying is 130. See the following table. x

Ix

dx

Wx

I’x

13–24

150

20

30

140

qx

px

Downloaded by Sturdy Drone (sturdydrone2707@gmail.com)

Px

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2. What is the probability of dying in those who did not die during the 25- to 36-month interval?

Use the following table to answer the question.

Survival of Patients With Metastatic Cancer Z Following Diagnosis Interval since beginning treatment (months)

Alive at beginning of interval

Died Withdre during w during interva interval l

Effective number exposed to risk of dying

Proporti on who died during interval

Proportion who did not die during interval

Cumulative proportion who survived from enrollment to end of interval

x

Ix

dx

Wx

I’x

qx

px

Px

1–12

200

10

40

13–24

150

20

30

25–36

100

30

20

37–48

50

40

10

a. 0.30 b. 0.33 c. 0.38 d. 0.67 e. 0.70 ANS: D The probability who did not die during interval of dying is defined as “1 minus proportion who died during interval.” The proportion who died during interval equals the “number of deaths during interval” divided by the “effective number exposed to risk of dying.” The effective number of exposed to risk of dying is defined as the “number of alive at beginning of interval” less “half of number withdrew during interval.” See the following table. x

Ix

dx

Wx

I’x

qx

px

Px

25–36

100

30

20

90

0.33

0.67

N/A

= The probability who did not die during interval of dying = 1 − dx/(Ix − ½  Wx) = 1 − 30/(100 − ½  20) = 0.67 3. What is the cumulative probability of surviving to the end of the 4-year follow-up period? Use the following table to answer the question.

Survival of Patients With Metastatic Cancer Z Following Diagnosis

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Interval since beginning treatment (months)

Alive at beginning of interval

Died Withdre during w during interva interval l

Effective number exposed to risk of dying

Proporti on who died during interval

Proportion who did not die during interval

Cumulative proportion who survived from enrollment to end of interval

x

Ix

dx

Wx

I’x

qx

px

Px

1–12

200

10

40

13–24

150

20

30

25–36

100

30

20

37–48

50

40

10

a. 0.06 b. 0.11 c. 0.54 d. 0.67 e. 0.89 ANS: A The cumulative probability of surviving (Px) is a multiplication of the probability of surviving each interval. For detailed calculation, see the following table. x

Ix

dx

Wx

I’x

qx

px

Px

1–12

200

10

40

180

0.06

0.94

0.94

13–24

150

20

30

135

0.15

0.85

0.80

25–36

100

30

20

90

0.33

0.67

0.54

37–48

50

40

10

45

0.89

0.11

0.06

4. What is the most important assumption in this type of analysis? Use the following table to answer the question.

Survival of Patients With Metastatic Cancer Z Following Diagnosis Interval since beginning treatment

Alive at beginning of interval

Died Withdre during w during interva interval l

Effective number exposed to risk of

Proporti on who died during

Proportion who did not die during interval

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Cumulative proportion who survived

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(months)

x

Ix

dx

Wx

1–12

200

10

40

13–24

150

20

30

25–36

100

30

20

37–48

50

40

10

dying

interval

I’x

qx

from enrollment to end of interval px

Px

a. There has been no secular (temporal) change in the effectiveness of treatment or in survivorship over calendar time. b. The effect of treatment has improved during the period of the study. c. The survival experience of people who are lost to follow-up is better than the experience of those who are followed up. d. The survival experience of people who are lost to follow-up is worse than the experience of those who are followed up. e. An equal number of men and women enrolled each year.

ANS: A There are two important assumptions made in using life-time table. The first one is that there has been no improvement on treatment effect. The second one is that the survival experience of people who are lost to follow-up is same as the experience of those who are followed up. “The effect of treatment has improved during the period of the study” is not correct. The treatment effect should be the same during the period of the study. “The survival experience of people who are lost to follow-up is better than the experience of those who are followed up” and “The survival experience of people who are lost to follow-up is worse than the experience of those who are followed up” are not correct. The survival experience of people who are lost to followup should be the same as the experience of those who are followed up. “An equal number of men and women enrolled each year” is not correct. An equal number of men and women enrolled in the study does not have any meaning in life-time table.

5. The following table describes the survival of patients treated from disease X from 2015 to 2017 followed for 3 years (assuming no loss to follow-up). What was the probability of surviving the third year?

Number alive at the end of year Year of treatment Number of patients treated 1 year 2 year 3 year 2015 100 67 42 30 2016 50 31 18 2017 75 52

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Totals

225

150

60

30

a. 0.29 b. 0.33 c. 0.61 d. 0.67 e. 0.71 ANS: E Please see calculations for each year: P1 = Probability of surviving the first year = 150/225 = 0.67, or 67% P2 = Probability of surviving the second year = 60/(150−52) = 0.61, or 61% P3 = Probability of surviving the third year = 30/(60−18) = 0.71, or 71% 6. The following table describes the survival of patients treated from disease X from 2015 to 2017 followed for 3 years (assuming no loss to follow-up). If a person is treated and using all the information from the table, what is the probability of surviving 3 years after treatment?

Number alive at the end of year Year of treatment Number of patients treated 1 year 2 year 3 year 2015 100 67 42 30 2016 50 31 18 75 2017 .5C2M Totals 225 15O 0 60 30 a. 0.29 b. 0.33 c. 0.61 d. 0.67 e. 0.71 ANS: A Please see calculations for each year: P1 = Probability of surviving the first year =150/225 = 0.67, or 67% P2 = Probability of surviving the second year = 60/(150−52) = 0.61, or 61% P3 = Probability of surviving the third year = 30/(60−18) = 0.71, or 71% Now the probability of surviving 3 years is the product of the probability of surviving each year.

Therefore 0.67  0.61  0.71 = 0.29, or 29%.

7. Which of the following illustrates a violation to one of the assumptions made when using the Kaplan-Meier method? a. Some patients who dropped out of the study have a similar probability of survival as those who remained in it. b. Patients present the outcome at different time intervals.

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c. An event of interest different from death is studied. d. There is a significant improvement in the treatment of the condition being studied in the middle of the duration of the study. e. The median survival time is longer than the duration of the study.

ANS: D A significant improvement in the treatment of the condition being studied is known as a secular (temporal) trend. One of the assumptions to use the Kaplan-Meier method is that no secular trends happen in the duration of the study.

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Chapter 07: Observational Studies Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which term most accurately describes the following definition?

“Analysis based on aggregated or grouped data; errors in inference may result because associations may be artifactually created or masked by the aggregation process.” [Porta M, ed. A Dictionary of Epidemiology. New York: Oxford University Press; 2014.] a. Ecologic study b. Cross-sectional study c. Case-control study d. Cohort study e. Randomized trial ANS: A Ecologic studies are studies of group characteristics to determine whether an association exists. “Cross-sectional study” is not correct. Cross-sectional studies define a population and determine the presence or absence of exposure and the presence or absence of disease for each individual at the same time. Both exposure and disease outcome are determined NU RScon IN GTstudy” B.CO simultaneously for each subject. “C asetrol is not correct. In case-control studies, investigators identify a group of individuals with the disease and a group of individuals without the disease to examine the possible relation of an exposure to a certain disease.

“Cohort study” is not correct. In cohort studies, investigators select a group of exposed individuals and a group of nonexposed individuals and follows up both groups to compare the incidence of disease in two groups. “Randomized trial” is not correct. A randomized trial is a clinical-epidemiologic experiment in which subjects are randomly allocated into groups, usually called test and control groups, to receive or not to receive a preventive or a therapeutic procedure or intervention.

2. Which term most accurately describes the following definition?

“A study that examines the relationship between diseases (or other health outcomes) and other variables of interest as they exist in a defined population at one particular time.” [Porta M, ed. A Dictionary of Epidemiology. New York: Oxford University Press; 2014.] a. Ecologic study b. Cross-sectional study c. Case-control study d. Cohort study e. Randomized trial ANS: B Cross-sectional studies define a population and determine the presence or absence of exposure and the presence or absence of disease for each individual at the same time. Both

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exposure and disease outcome are determined. “Ecologic study” is not correct. Ecologic studies are studies of group characteristics to determine whether an association exists. “Casecontrol study” is not correct. In case-control studies, investigators identify a group of individuals with the disease and a group of individuals without the disease to examine the possible relation of an exposure to a certain disease. “Cohort study” is not correct. In cohort studies, investigators select a group of exposed individuals and a group of nonexposed individuals and follows up both groups to compare the incidence of disease in two groups.

“Randomized trial” is not correct. A randomized trial is a clinical-epidemiologic experiment in which subjects are randomly allocated into groups, usually called test and control groups, to receive or not to receive a preventive or a therapeutic procedure or intervention.

3. Which term most accurately describes the following definition?

“The observational epidemiological study of persons with the disease (or another outcome variable) of interest and a suitable control group of persons without the disease (comparison group, reference group).” [Porta M, ed. A Dictionary of Epidemiology. New York: Oxford University Press; 2014.] a. Ecologic study b. Cross-sectional study c. Case-control study d. Cohort study e. Randomized trial ANS: C In case-control studies, investigatoNrU s iR deSnI tifNyG aT gB ro. upCoOf M individuals with the disease and a group of individuals without the disease to examine the possible relation of an exposure to a certain disease. “Ecologic study” is not correct. Ecologic studies are studies of group characteristics to determine whether an association exists. “Cross-sectional study” is not correct. Cross-sectional studies define a population and determine the presence or absence of exposure and the presence or absence of disease for each individual at the same time. Both exposure and disease outcome are determined simultaneously for each subject. “Cohort study” is not correct. In cohort studies, investigators select a group of exposed individuals and a group of nonexposed individuals and follows up both groups to compare the incidence of disease in two groups. “Randomized trial” is not correct. A randomized trial is a clinicalepidemiologic experiment in which subjects are randomly allocated into groups, usually called test and control groups, to receive or not to receive a preventive or a therapeutic procedure or intervention.

4. Which of the following statements is not the accurate description of selection bias in casecontrol studies? a. If cases are selected from a single hospital, any risk factors that are identified may be unique to that hospital. b. If the hospital from which the cases are drawn is a tertiary care facility, any risk factors identified in the study may be risk factors only in persons with severe forms of the disease. c. If hospitalized cases are to be used, it is desirable to select the cases from several hospitals in the community. d. Using hospitalized patients as controls is the best way to characterize the reference population because they are a captive population and are clearly identified.

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e. Best friends controls and neighborhood controls are examples of use of nonhospitalized people as controls.

ANS: D Hospitalized patients represent a sample of an ill-defined reference population, not the general reference population. Moreover, hospital patients differ from people in the community. Therefore using hospitalized patients as controls is not the best way to characterize the reference population. The best way to characterize the reference population is using nonhospitalized people as controls with probability sampling from the community (but rarely possible).

5. Which of the following biases is the most accurate explanation of the following situation?

Epidemiologists are studying the possible relationship of cholera infections to drinking water.

They conduct a case-control study and interview patients with cholera infection (cases) and persons without cholera infection (controls). A patient who was diagnosed with cholera often tries to identify all kinds of information related to drinking water. However, controls who were not diagnosed with cholera may not remember water they drink which is not from an unhygienic source. a. Recall bias b. Selection bias c. Misclassification bias d. Publication bias e. Exclusion bias ANS: A In a case-control study, cases are more likely to recall exposures that they believe may have contributed to the outcome. “Selection bias,” “Misclassification bias,” “Exclusion bias” are related to the selection of cases. “Publication bias” is about bias observed in published articles.

6. In the paper [Gold E, Gordis L, Tonascia J, et al. Risk factors for brain tumors in children.

Am J Epidemiol. 1979;109(3):309–319], investigators conducted a case-control study to identify risk factors for brain tumors in children. Children with brain tumors were compared with two groups of controls: The first control group, called normal controls, consisted of children with no known malignant disease. The second control group, called cancer controls, consisted of children with malignancies other than brain tumors. What is the benefit of using multiple controls in case-control studies? a. This may reduce the recall bias from participants. b. This may reduce the selection bias for participation. c. This may reduce the potential confounders from investigators. d. This may reduce the placebo effect from participants. e. None of above.

ANS: A

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Cases are more likely to recall exposures that they believe may have contributed to the outcome. In this case, cancer controls are also likely to remember previous exposures, then we may reduce recall bias. “This may reduce the selection bias for participation” might be guaranteed by choosing community controls instead of hospital controls. “This may reduce the potential confounders from investigators” is acquired by randomization. “This may reduce the placebo effect from participants” is an explanation about blinding (masking) in clinical trial.

7. Epidemiologists tried to examine the distribution of multimorbidity, and of comorbidity of physical and mental health disorders, in relation to age and socioeconomic deprivation. They extracted data on 40 morbidities from a database of 1,751,841 people registered with 314 medical practices in Scotland as of March 2007. They analyzed the data according to the number of morbidities, disorder type (physical or mental), sex, age, and socioeconomic status. They defined multimorbidity as the presence of two or more disorders. [From Barnett K, Mercer SW, Norbury M, et al. Epidemiology of multimorbidity and implications for health care, research, and medical education. Lancet. 2012;380(9836):37–43.] What is the proper classification for this study? a. Cross-sectional study b. Prospective cohort study c. Case-control study d. Randomized trial e. Case report ANS: A Because this study captured all data from 1,751,841 individuals at the same time (with exposure and outcome), cross-sectional study is the most accurate classification of the study.

“Prospective cohort study” is not correct; they did not follow up the participants. “Casecontrol study” is not correct; they did not classify participants by disease status. “Randomized trial” is not correct; they did not randomly allocate exposure status. “Case report” is not correct; they did not report a single or series of disease cases.

8. Researchers wanted to provide additional support for a causal association between human papillomavirus (HPV) and oropharyngeal cancers. They performed an epidemiologic study of 100 patients with newly diagnosed oropharyngeal cancer and 200 control patients without cancer to evaluate associations between HPV infection and oropharyngeal cancer. [D’souza G, Kreimer AR, Viscidi R, et al. A study of human papillomavirus and oropharyngeal cancer.

N Engl J Med. 2007;356(19):1944–1956.] What kind of study design is this? a. Retrospective cohort study b. Prospective cohort study c. Case-control study d. Randomized trial e. Case report ANS: C Investigators classified participants by disease status, cases, and controls, then investigated the exposure status. “Retrospective cohort study” and “Prospective cohort study” are not

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correct; they did not follow up the participants in either direction. “Randomized trial” is not correct; they did not randomly allocate exposure status. “Case report” is not correct; they did not report a single or series of disease cases.

9. A researcher study of Baltimore’s neighborhoods showed that those neighborhoods with lower median household income experienced a higher teen pregnancy rate. What type of study design was used? a. Cohort b. Case-control c. Ecologic d. Experimental e. Randomized trial ANS: C Ecologic studies are characterized by studying groups of people (in this case, neighborhoods) rather than individuals.

10. A researcher study of Baltimore neighborhoods showed that those with lower median household income experience a higher teen pregnancy rate. After reading this, someone concludes that a teenager with low income is more likely to get pregnant. What is the name of this mistaken conclusion? a. Selection bias b. Information bias c. Confounding d. Ecologic fallacy e. Group misinterpretation ANS: D Ecologic fallacy is making individual-level conclusions from ecologic studies, which collect group-level data.

11. A group of physicians working in the same hospital noticed a rare presentation of male young patients, free of typical risks factors, who presented to the hospital with rapidly progressing acute kidney failure. They documented their findings and described in detail the progression of disease. What is the study design described here? a. Case report b. Case series c. Cohort study d. Ecologic study e. Meta-analysis ANS: B

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The study described is a case series, where a group of patients under observation are comprehensively described. It is not a case report because, in this case, multiple patients were identified.

12. To determine the prevalence of smoking among new students in a university, researchers conduct an anonymous survey at the first day of classes. They find that 22% of women and 28% of men were smokers. What type of study design was used? a. Ecologic b. Cross-sectional c. Cohort d. Case-control e. Systematic review ANS: B This type of surveys, in which participants are seen once by researchers and several variables are measured at one time point, is called cross-sectional studies. These studies are particularly good to estimate the prevalence of a disease or exposure; for that reason, they are also called “prevalence studies.”

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Chapter 08: Cohort Studies Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Some researchers want to investigate the association of work stress and risk of cardiovascular mortality. Investigators selected a systematic sample of 902 participants in strata by sex, age, and occupational group from the Valmet factories in Jyväskylä, in central Finland. Baseline examination in 1973 determined cases of cardiovascular disease, behavioral and biologic risks, and stressful characteristics of work. Follow-up examinations included measurement of blood pressure, cholesterol concentration, and body mass index in 1978 and in 1983. [Kivimäki M, Leino-Arjas P, Luukkonen R, et al. Work stress and risk of cardiovascular mortality: a study of industrial employees. BMJ 2002;325(7369):857.] What kind of study design is this? a. Cross-sectional study b. Prospective cohort study c. Case-control study d. Randomized trial e. Case report ANS: B Investigators defined their exposure (work stress), followed up the participants, and measured outcome (cardiovascular mortality). “Cross-sectional study” is not correct; they did not capture all information (exposure and outcome) from participants at the same time. “Casecontrol study” is not correct; they did not classified participants by disease status.

“Randomized trial” is not correct; they did not randomly allocate exposure status. “Case report” is not correct; they did not report a single or series of disease cases.

2. Which of the following statements is the most accurate characteristic of cohort studies? a. It is an efficient study designs for studying rare disease. b. The temporality of the exposure preceding the outcome is hard to determine. c. The incidence rate of disease in the exposure group is compared directly to the incidence rate of disease in the unexposed group. d. The exposure and outcomes are captured at the same time. e. The participants are randomly allocated to exposure and nonexposure categories.

ANS: C The incidence rate of disease in the exposure group is compared directly to the incidence rate of disease in the unexposed group because direct comparison of incidence rate, the risk, is one of the most distinctive characteristics of cohort study. “It is an efficient study designs for studying rare disease” is not correct. A cohort study is not an efficient study design for studying a rare disease. “The temporality of the exposure preceding the outcome is hard to determine” is not correct. The temporarily of the exposure preceding the outcome is easy to

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determine. “The exposure and outcomes are captured at the same time” is not correct. In a cohort study, exposure is measured at the beginning of the study, then outcomes are captured.

“The participants are randomly allocated to exposure and nonexposure categories” is not correct. In a cohort study, investigators cannot allocate the exposure status; this is an explanation of randomized clinical trial.

3. Which of the following statements is the most accurate characteristic of the nested casecontrol study? a. A control who is selected early in the study could later develop the disease but cannot be a case in the same study. b. In nested case-control studies, controls are a sample of individuals who are at risk for the disease at the time each case of disease develops. c. Controls are randomly chosen from the defined cohort with which the study began. d. The problems of possible recall bias from conventional case-control studies still remains. e. Nested case-control studies are often less economical to conduct.

ANS: B In a nested case-control study, controls are selected from noncases individuals (who are at the risk) when cases are selected. “A control who is selected early in the study could later develop the disease but cannot be a case in the same study” is not correct. A control who is selected early in the study can be a case in the same study later (when the case develops the disease at that time). “Controls are randomly chosen from the defined cohort with which the study began” is not correct and is an explanation of controls in a case-cohort study Control is selected when the case is defined.N. U “TRhS eI prN obGleTmBs. oC f pOoM ssible recall bias from conventional case-control studies still remains” is not correct. Because a nested case-control is conducted based on an earlier existing cohort study, recall bias from a conventional case-control study can be eliminated. “Nested case-control studies are often less economical to conduct” is not correct. Because a nested case-control is conducted based on an earlier existing (cohort) study, it is normally considered more economical to conduct.

4. In which of the following study designs is possible to calculate incidence rate? a. Cross-sectional b. Case-control c. Cohort d. Case-series e. Report of a case ANS: C To calculate incidence, it is necessary to follow up a group of individuals without the disease to detect new cases. The only option that describes such a study is a cohort study.

5. The Baltimore Longitudinal Study of Aging (BLSA) is a research study of normative aging started in the 1950s. Volunteers, free of chronic conditions, are recruited and followed every 4, 2, or 1 year(s) until their death. What type of study design is this? a. Cross-sectional

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b. Ecologic c. Randomized trial d. Retrospective cohort e. Prospective cohort ANS: E This is a prospective observational longitudinal study. These characteristics are unique of a prospective cohort study.

6. The main difference between a cohort study and a randomized trial is that a. cohort studies are longitudinal and randomized trials are cross-sectional. b. only clinical trials can evaluate the effect of a drug. c. randomized trials are experimental and cohort studies are observational. d. clinical trials are observational and cohort studies are experimental. e. at the beginning of a clinical trial, participants are free of disease, and cohort studies start with patients with a disease.

ANS: C Clinical trials are experimental studies in which participants are randomly assigned to receive an intervention. Cohort studies are observational; participants carry on with their usual lifestyle without any assignment by researchers.

7. In 1999 the army of country Z sNtaUrtR edStI oN coGllT ecB t. daC taOfM rom all their recruits. As part of the process, they conducted a full physical examination in which audition was measured and reported as normal hearing, low hearing loss, and severe hearing loss. Unfortunately, 5 years later country Z went into a war with country Y. In 2018 a researcher from University U decided to conduct a study in which she investigated the association between hearing loss and suffering a war injury. What type of study design is being illustrated in this example? a. Case-control study b. Cross-sectional study c. Ecologic study d. Prospective cohort study e. Retrospective cohort study ANS: E The study design described in this question is a retrospective cohort in which the exposure to hearing loss was ascertained from past records collected by the army.

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Chapter 10: Assessing Preventive and Therapeutic Measures: Randomized Trials Celentano: Gordis Epidemiology, 6th Edition Test Bank MULTIPLE CHOICE 1. Participants in a clinical trial might report different symptoms when they know they are part of the intervention group instead of the control group. To avoid that, researchers use the following: a. Confounding b. Randomization c. Concealment of random allocation d. Masking e. Effect modifiers ANS: D Masking is used to prevent participants from knowing whether they are receiving an intervention (most times a drug) or a control (placebo). hU t iR nfS luI enNcG eT thB e. seC leO ctM ion of participants into a group 2. In a clinical trial, researchers migN (intervention or control), hence introducing bias into the study. What can be done to prevent from this threat to the validity of the study? a. Confounding b. Randomization c. Concealment of random allocation d. Masking e. Effect modifiers ANS: B The main purpose of randomization is to prevent the potential bias on the part of the investigators from assigning participants into the groups of the trial.

3. In a clinical trial, sometimes patients agree to receive an intervention but later decide to stop taking the medication. Moreover, some patients who were assigned to placebo decide to stop taking the placebo pill and buy the drug on their own (even when they do not know that they are taking a placebo pill). When this happens, researchers typically do the analysis according to the original assignment of the treatment regardless of the actual treatment received. What is the name of this procedure to analyze the data? a. Randomization

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b. Intention-to-treat analysis c. Concealment of random allocation d. Analysis as treated e. Mediation analysis ANS: B Regardless of the actual treatment that patients receive, researchers typically analyze the data respecting the original assignment of patients to the study arms. For example, a patient is assigned to receive treatment A (taking a pill daily), but he decides to stop taking such pill.

When the analysis is done, this patient will be categorized into the treatment A group. This analysis is called intention-to-treat.

4. Two similar drugs (drug A and drug B) to alleviate back pain were released simultaneously.

An investigator decides to test which of the drugs works better. He decides to conduct a trial in which randomly, half of the participants receive drug A for a month while the other half received drug B. After 2 weeks without any medication, participants switch the drug they were receiving (those who received A start taking B, and those who received B start taking A). What type of study design was illustrated in this example? a. Cross-sectional study b. Factorial randomized clinical trial c. Crossover randomized clinical trial d. Crossover cohort study e. Phase II clinical trial ANS: C In a crossover clinical trial, participants receive one drug and later switch to another one. The effect of these drugs is compared within the same population.

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Chapter 11: Randomized Trials: Some Further Issues Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. What is the primary purpose of randomization? a. To prevent bias in the assignment of treatment b. To provide a probability basis for statistical testing c. To ensure the same number of people are randomized to each group d. To ensure that the subjects not to know which group they are assigned to e. To guarantee the comparability of the different treatment groups ANS: A The primary purpose of randomization is to reduce the bias from investigator to assign the treatment to participants. “To provide a probability basis for statistical testing” is not correct.

Probability basics are not related with randomization. “To ensure the same number of people are randomized to each group” is not correct. The same number of people to each group can be guaranteed by other ways such as exclusion or dropping participants. “To ensure that the subjects not to know which group they are assigned to” is not correct and this is a description of blinding (masking). “To guarantee the comparability of the different treatment groups” is NUtion RSinc INreas GTesB.C not correct. Even though randomiza the cOomparability of different treatment group, it cannot guarantee the comparability and it is not the primary purpose of randomization.

2. Epidemiologists decided to investigate the effect of sunscreens on sunburns. They ran an epidemiologic study to see the association of sunscreens and sunburns. Overall, 460 people have enrolled in the study. Investigators randomly allocated 230 people to the treatment group (sunscreens) and 230 to the control group (placebo). They exposed those 460 people to the high mountain trail on a sunny day. At the end of the study, 30 people developed sunburns in the sunscreen group and 130 people developed sunburns in the placebo group.

What type of study design is this? a. Cross-sectional study b. Prospective cohort study c. Case-control study d. Randomized trial e. Case-control study ANS: D Investigators randomly allocated the exposure status to the participants. Therefore it is a randomized trial. “Cross-sectional study” is not correct because they did not capture exposure and outcome status at the same time. “Prospective cohort study” is not correct because they did not recruit the people based on their exposure status. “Case-control study” is not correct

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because they did not define the people based on their outcome status. “Case-control study” is not correct because they did not report a case or series of cases.

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Chapter 12: Estimating Risk: Is There an Association?

Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Epidemiologists decided to investigate the effect of sunscreens on sunburns. They ran an epidemiologic study to see the association of sunscreens and sunburns. Overall, 460 people have enrolled in the study. Investigators randomly allocated 230 people to the treatment group (sunscreens) and 230 to the control group (placebo). They exposed those 460 people to the high mountain trail on a sunny day. At the end of the study, 30 people developed sunburns in the sunscreen group and 130 people developed sunburns in the placebo group.

What is the risk of developing sunburns in the placebo group? a. 0.13 b. 0.15 c. 0.23 d. 0.57 e. 1 ANS: D The population at risk in the placebo group is 230, and the number of positive outcomes RSThe INrefo GTreB.C M of developing sunburns in the (sunburns) in the placebo group isN1U 30. the rO isk placebo group is 0.57 (130 divided by 230).

2. Epidemiologists decided to investigate the effect of sunscreens on sunburns. They ran an epidemiologic study to see the association of sunscreens and sunburns. Overall, 460 people have enrolled in the study. Investigators randomly allocated 230 people to the treatment group (sunscreens) and 230 to the control group (placebo). They exposed those 460 people to the high mountain trail on a sunny day. At the end of the study, 30 people developed sunburns in the sunscreen group and 130 people developed sunburns in the placebo group.

What is the relative risk of sunburns in the sunscreen treatment group compared with the control group in this study? a. 0.12 b. 0.13 c. 0.23 d. 1.33 e. 4.33 ANS: C The risk of sunburns in the exposure group is 30 divided by 230 (0.13), and the risk of sunburns in the placebo group is 130 divided by 230 (0.57). The relative risk is 0.23 (0.1 divided by 0.57).

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3. The following information summarizes the exercise status and obesity status in a casecontrol study. What are the odds of regular exercise in the obesity group? Use the following table to answer the question.

Exercise Status by Obesity Status Obesity status Yes

No

Yes (regular exercise)

7

27

No (no exercise)

43

73

Exercise status

a. 0.16 b. 0.26 c. 0.37 d. 0.44 e. 0.59 ANS: A The number of regular exercise in the obesity group is 7, and the number of no exercise in the same group is 43. Therefore the odds of exercise in the obesity group is 0.16 (7 divided by 43).

4. The following information summarizes the exercise status and obesity status in a casecontrol study. What is the odds ratio of regular exercise in this study? Use the following table to answer the question.

Exercise Status by Obesity Status Obesity status Yes

No

Yes (regular exercise)

7

27

No (no exercise)

43

73

Exercise status

a. 0.16 b. 0.26 c. 0.37 d. 0.44 e. 0.59 ANS: D

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The odds of exercise in the obesity group is 7 divided by 43 (0.163), and the odds of exercise in the nonobesity group is 27 divided by 73 (0.370). The odds ratio is 0.44 (0.163 divided by 0.370).

5. What is the estimated odds ratio of cases when analyzing this study as a matched casecontrol study design? Use the information from a case-control study table.

Exposure Status by Disease Status Pair no.

Cases

Controls

1

Exposed

Unexposed

2

Exposed

Exposed

3

Unexposed

Exposed

4

Exposed

Unexposed

5

Exposed

Unexposed

6

Unexposed

Exposed

7

Exposed

Exposed

8

Unexposed

Unexposed

9

Exposed

Unexposed

10

NURSIN Unexposed

Unexposed

11

Exposed

Exposed

12

Unexposed

Exposed

13

Exposed

Unexposed

14

Exposed

Unexposed

15

Unexposed

Unexposed

a. 0.50 b. 0.67 c. 1.00 d. 2.00 e. 2.25 ANS: D The number of exposed pairs is 3, the number of exposed-case and unexposed-control pairs is 6, the number of unexposed-case and exposed-control pairs is 3, and the number of unexposed pairs is 3. Therefore the odds ratio from matched case-control study is (number of exposed-case and unexposed-control pair) divided by (number of unexposed-case and exposed-control pair); 6 divided by 3 equals 2.

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6. Unmatch the pairs. What are the estimated odds of exposure in controls when analyzing this study as an unmatched case-control study design? Use the information from a casecontrol study table.

Exposure Status by Disease Status Pair no.

Cases

Controls

1

Exposed

Unexposed

2

Exposed

Exposed

3

Unexposed

Exposed

4

Exposed

Unexposed

5

Exposed

Unexposed

6

Unexposed

Exposed

7

Exposed

Exposed

8

Unexposed

Unexposed

9

Exposed

Unexposed

10

Unexposed

Unexposed

11

N ExUpR osS edI

Exposed

12

Unexposed

Exposed

13

Exposed

Unexposed

14

Exposed

Unexposed

15

Unexposed

Unexposed

a. 0.50 b. 0.67 c. 1.00 d. 2.00 e. 2.25 ANS: B The odds of exposure among controls is found by dividing the number of exposed people among controls (6) by 9 (the number of unexposed people among controls), which equals 0.67.

7. Unmatch the pairs. What is the estimated odds ratio of cases when analyzing this study as an unmatched case-control study design? Use the information from a case-control study table.

Exposure Status by Disease Status

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Pair no.

Cases

Controls

1

Exposed

Unexposed

2

Exposed

Exposed

3

Unexposed

Exposed

4

Exposed

Unexposed

5

Exposed

Unexposed

6

Unexposed

Exposed

7

Exposed

Exposed

8

Unexposed

Unexposed

9

Exposed

Unexposed

10

Unexposed

Unexposed

11

Exposed

Exposed

12

Unexposed

Exposed

13

Exposed

Unexposed

14

NURS

Exposed

Unexposed

15

Unexposed

Unexposed

a. 0.50 b. 0.67 c. 1.00 d. 2.00 e. 2.25 ANS: E The odds ratio of exposure among controls is found by dividing 1.5 (the odds of exposed people among cases) by the odds of exposed people among controls (2 over 3, which equals 2.25).

8. Which of the following measures represents the absolute risk of getting a disease? a. Prevalence b. Odds ratio c. Risk ratio d. Incidence e. Risk difference

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ANS: D The incidence of a disease is the only measure of absolute risk. Prevalence represents the proportion of people who have a disease at a certain time point or period, but only the incidence provides information about the chances of getting a disease because it considers only new cases. Odds ratio, risk ratio, risk difference represent measures of risk that compare two groups, usually exposed and unexposed.

9. The following table summarizes the findings of a cohort study. Participants were enrolled in January 1, 2015, and followed up until December 31, 2015. Researchers were interested in the effect of physical activity on cardiovascular disease.

Cardiovascular events No events Total Physically active 28 1,972 2,000 Inactive 75 2,925 3,000 Based on the previous information, calculate the incidence per 1,000 per year of cardiovascular events among those who were categorized as physically active. a. 14/1,000 per year b. 25/1,000 per year c. 28/1,000 per year d. 75/1,000 per year e. 99/1,000 per year ANS: A Incidence in that group is calculated by dividing the number of events over the total number of participants in that group (28/2,000 = 0.014).

10. The following table summarizes the findings of a cohort study. Participants were enrolled in January 1, 2015, and followed up until December 31, 2015. Researchers were interested in the effect of physical activity on cardiovascular disease.

Cardiovascular events No events Total Physically active 28 1,972 2,000 Inactive 75 2,925 3,000 Based on the previous information, calculate the relative risk of cardiovascular events for those who were physically active. a. 0.38 b. 0.56 c. 1.50 d. 1.79 e. 2.68 ANS: B The risk for active participants is 14/1,000 per year, and the risk for inactive is 25/1,000 per year. Thus the relative risk is calculated as follows: (14/1,000)/(25/1,000) = 0.56.

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11. Consider the following 2  2 table from a hypothetical cohort study. Calculate the incidence of cardiovascular disease (CVD) among the not exposed participants.

Serum fasting glucose Developed CVD Did not develop CVD Total 126 mg/dL (exposed) 125 325 450 <126 mg/dL (not exposed) 50 500 550 Total 175 825 1000 a. 9 per 100 population b. 28 per 100 population c. 44 per 100 population d. 50 per 175 population e. 72 per 100 population ANS: A In a 2  2 table that is setup in this format, we can apply the formula: c/(c + d) to calculate the incidence of disease in the not exposed group: 50/(50 + 500) = 0.09  100 = 9% or 9 per 100 population.

12. Consider the following 2  2 table from a hypothetical cohort study. Calculate the relative risk of CVD comparing those with high fasting glucose (126 mg/dL) with those with normal fasting glucose (<126 mg/dL) Serum fasting glucose Developed CVD Did not develop CVD Total 25TB.C M 126 mg/dL (exposed) N RSIN1G 325 450 <126 mg/dL (not exposed) 50 500 550 Total 175 825 1000 a. 0.33 b. 0.75 c. 1.02 d. 3.08 e. 5.34 ANS: D In a 2  2 table that is set up in this format, we can apply the formula: (a/(a + b))/(c/(c + d)) to calculate the relative risk: (125/(125 + 325))/(50/(50 + 500)) = 3.08.

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Chapter 13: More on Risk: Estimating the Potential for Prevention Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. What is the best measure of association to explain what percentage of the new diagnoses of disease X are explained by exposure to Y among those exposed to Y? a. Relative risk b. Risk ratio c. Odds ratio d. Attributable risk e. Incidence rate ratio ANS: D The attributable risk is the measure of association that explain what proportion of the cases are due to a particular exposure among the people exposed to that particular factor.

2. A politician asks an epidemiologist how many cases of coronary heart disease can be prevented if they manage to eliminate the exposure to smoking in city A. The epidemiologists explain that, if they eliminate smoking, they could prevent 22% cases of coronary heart Nn R I sed GTtoB.C disease. What measure of associatioU wS as uN answOer this question? a. Population attributable risk b. Odds ratio c. Relative risk d. Incidence rate e. Risk ratio ANS: A The population attributable risk is a measure that allows to calculate the proportion of cases that are due to a particular exposure in a particular population.

3. The incidence of disease X is 56/1,000 per year among smokers and 33/1,000 per year among nonsmokers. What proportion of cases of disease X are due to smoking among those who smoke? a. 23% b. 33% c. 41% d. 56% e. 59% ANS: C

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In other words, this question asks for the attributable risk. The attributable risk is calculated as follows: (incidence in exposed − incidence in unexposed)/(incidence in exposed); in this example: (56/1,000 − 33/1,000)/(56/1,000) = 0.41, or 41%.

4. In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. What is the relative risk of smoking in this cohort study? a. 0.5 b. 1.7 c. 3.5 d. 4.8 e. 7.5 ANS: D Because this study is a cohort study, the incidence rate can be considered as a risk. The risk of myocardial infarction among smokers is found by dividing 250 by 7,000. The risk of myocardial infarction among nonsmokers is found by dividing 150 by 20,000. The relative risk of myocardial infarction is 35.7 per 1,000 divided by 7.5 per 1,000, which equals 4.8.

5. In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. What is the attributable risk (risk N R I G B.C M difference) of smoking?

U S N T O a. 2.8 per 1,000 b. 3.6 per 1,000 c. 7.5 per 1,000 d. 28.2 per 1,000 e. 35.7 per 1,000 ANS: D

The attributable risk, risk difference, equals the incidence in the exposed minus the incidence in the nonexposed. In this study, the incidence of myocardial infarction among smokers is 35.7 per 1,000 and the incidence among the nonexposed is 7.5 per 1,000. Subtracting the latter from the former, the difference in the incidence rate is 28.2 per 1,000.

6. In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. From another source, a cross-sectional study, we know that 30% of the total population in City A were smokers. What is the population proportion attributable risk of smoking in City A? a. 15% b. 30% c. 53% d. 79%

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e. 90% ANS: C The population proportion attributable risk (PPAR) equals the incidence in the total population minus the incidence in the nonexposed divided by the incidence in the total population. In this data, the total population incidence is 35.7 times 0.3 plus 7.5 times 0.7.

This gives a total population incidence of 16.0 per 1,000 persons. Using the total population incidence in the PPAR calculation then gives an estimate of 53%. This is found by subtracting 7.5 from 16.0 and dividing this result by 16.0.

7. Which of the following statements is the most accurate description of the risk and relative risk of lung cancer deaths in this study? Use the following information: Lung Cancer and Coronary Health Disease Mortality by Smoking Status Age-adjusted death rates per 100,000 Smokers

Nonsmokers

Lung cancer

150

70

Coronary heart disease

700

300

[Modified from Doll R, Peto R. Mortality in relation to smoking: 20 years’ observations on male British doctors. Br Med J. 1976;2(6051):1525–1536.] a. The risk of lung cancer deaths is 2.1 times greater in smokers compared with nonsmokers.

INs GleTssB.C b. The risk of lung cancer deaths isNU 2.1RS time in smOokers compared with nonsmokers. c. Because investigators followed up participants over 20 years, deaths rate cannot be used as a risk. d. The risk of lung cancer deaths among smokers is 70 per 100,000. e. The risk of lung cancer deaths among nonsmokers is 150 per 100,000.

ANS: A In this study, investigators followed up participants over 20 years, which indicated that this study is a cohort study. In a cohort study, an age-adjusted death rate (or cumulative incidence) can be used as a risk. The risk of lung cancer deaths among smokers is 150 per 100,000, and the risk of lung cancer deaths among nonsmokers is 70 per 100,000. The relative risk of lung cancer deaths by smoking 150 divided by 70, which equals 2.1. This can be interpreted to indicate that “the risk of lung cancer deaths is 2.1 times greater in smokers compared with nonsmokers.”

8. Which of the following statements is the most accurate description of the attributable risk (deaths per 100,000) of coronary heart disease for smokers in this study? Use the following information: Lung Cancer and Coronary Health Disease Mortality by Smoking Status Age-adjusted death rates per 100,000 Smokers

Nonsmokers

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Lung cancer

150

70

Coronary heart disease

700

300

[Modified from Doll R, Peto R. Mortality in relation to smoking: 20 years' observations on male British doctors. Br Med J. 1976;2(6051):1525–1536.] a. The attributable risk of coronary heart disease deaths is 700 deaths per 100,000. b. The attributable risk of coronary heart disease deaths is 400 deaths per 100,000. c. Attributable risk cannot be used as an indicator of the disease burden reduction that could be achieved if the risk factor eliminated. d. The risk of coronary heart disease deaths among smokers is 70 per 100,000. e. The risk of coronary heart disease deaths among nonsmokers is 30 per 100,000.

ANS: B The attributable risk equals the incidence rate in the exposed group minus the incidence rate in the nonexposed group. The risk of coronary heart disease deaths among smokers is 700 per 100,000, and the risk of coronary heart disease deaths among nonsmokers is 300 per 100,000.

The attributable risk is 400 per 100,000. This estimate is interpreted to mean that 300 of the 700 incident cases of coronary heart disease deaths occurring in 100,000 individuals among smokers are due to the smoking exposure itself.

9. The following is a measure of the strength of association, typically used in case-control studies to measure the association between exposure and disease: a. Incidence rate b. Population attributable fraction c. Attributable fraction d. Prevalence e. Odds ratio ANS: E Odds ratio is a measure of the strength of an association that is typically used in case-control studies. “Population attributable fraction” and “attributable fraction” describe measures of the potential preventive effect of eliminating an exposure. “Incidence rate” and “prevalence” describe measures of disease frequency.

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Chapter 14: From Association to Causation: Deriving Inferences From Epidemiologic Studies Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Lack of physical activity is a known factor associated with colon cancer. However, colon cancer develops even among active individuals. Moreover, several individuals who perform very little levels of physical activity never develop colon cancer. Hence, in the causal relationship between physical inactivity and colon cancer, the lack of physical activity is a. necessary and sufficient. b. sufficient but not necessary. c. necessary but not sufficient. d. neither necessary not sufficient. e. confounded.

ANS: D Based on the previous information, physical inactivity is neither necessary nor sufficient to cause colon cancer.

N R I G B.C M

U asS VO N 2 max T in mL/kg/min O 2. Cardiorespiratory fitness, measured (maximum oxygen consumption), is associated with increased longevity. Recent evidence suggests that higher fitness increases the life span. Those with a low VO2 max have a life expectancy after 60 years of 7 years, those with moderate VO2 max of 15 years, and those with a high VO2 max have a life expectancy after 60 of 23 years. Which of the causal criteria is illustrated with this example? a. Temporal relationship b. Strength of association c. Replicability of findings d. Specificity of association e. Dose-response effect ANS: E This example shows a dose-response effect, where increasing fitness is associated with increased life expectancy after age of 60.

3. Temporal relationship is a necessary criterion to establish causality. Which of the following epidemiologic study design allows to evaluate temporal relationship? a. Cross-sectional b. Case-control c. Transversal d. Cohort

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e. Literature review ANS: D Among these options, only cohort studies have follow-up; therefore only these studies can show whether an exposure precedes the outcome of interest. Longitudinal study is necessary to show temporal relationship.

4. Which of the following statements is not evidence suggesting Exposure A as a causative agent on Disease X? a. Exposure A is clearly linked to mediator M. Approximately 11% of mediator M patients will go on to have Disease X over a 10-year period. b. Many of the observations regarding Exposure A and Disease X have been replicated repeatedly. c. Prevalence of Exposure A in patients with Disease X is 90% to 100%. d. Eradication of Exposure A heals Disease X at the same rate as other treatment of choice. e. None of above ANS: E All of the answers suggest causal relationship between exposure and outcome. “Exposure A is clearly linked to mediator M. Approximately 11% of mediator M patients will go on to have Disease X over a 10-year period” indicates the temporal relationship. “Many of the observations regarding Exposure A and Disease X have been replicated repeatedly” indicates replication of the findings. “PrevaN leU ncReS oI f ENxG poTsB ur. eC AOinMpatients with Disease X is 90% to 100%” means there is specificity of the association. “Eradication of Exposure A heals Disease X at the same rate as other treatment of choice” is a cessation of exposure. All of the answers indicate that Exposure A is a causative agent for Disease X. 5. Human papillomavirus (HPV) infections are known to be a cause of cervical cancer. In most cases, HPV goes away on its own and does not cause any health problems. However, the worldwide HPV prevalence in cervical carcinomas is 99.7%. This indicates that HPVnegative carcinoma is extremely uncommon. In this case, HPV is which of the following? a. A necessary and sufficient cause b. A necessary but not sufficient cause c. A sufficient but not necessary cause d. Neither necessary nor sufficient e. None of the above ANS: B Because most of all cervical cancer patients present HPV infection, this indicates that HPV is a necessary cause for cervical cancer. However, all HPV infection does not develop as cervical cancer, which means HPV is not sufficient to cause for cervical cancer. Therefore HPV is a necessary but not sufficient cause.

6. In a hypothetical cross-sectional study, marriage was found to be strongly associated with increased levels of happiness. Authors concluded that marriage was a cause of happiness.

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However, a reviewer of this study argued that because it is a cross-sectional study, it could not be determined whether marriage caused happiness or happiness caused marriage. What criterion of causal relationships was not met in the study according to the reviewer? a. Strength of association b. Biologic plausibility c. Dose response d. Temporal relationship e. Replication of findings ANS: D A temporal relationship cannot be assessed in a cross-sectional study; therefore it is not possible to assess whether marriage leads to happiness or happy people are more likely to get married. This criterion has to be met to establish causality.

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Chapter 15: More on Causal Inference: Bias, Confounding, and Interaction Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Smoking participants of a cohort study are more likely to drop out. It is known that the effect of asbestos on getting cancer is much stronger among smokers. When analyzing data for this study, researchers find no association between asbestos and cancer. A potential explanation for the results of the study is a. confounding. b. effect modification. c. selection bias. d. information bias. e. specificity of association.

ANS: C Because those participants who dropped the study were particular regarding the association (smokers), those who remained in the study showed a biased attenuated association.

2. In a case-control study, a researcher found no association between exposure to A and RSwa INs Ga Tmisclas B.COsification when measuring exposure to disease B. Later she found out thatNtU here A, in both cases and controls. What is a potential explanation for the results (no association) of this case-control study? a. Nondifferential misclassification b. Differential misclassification c. Selection bias d. Confounding e. Effect-modification ANS: A This is an example of nondifferential misclassification. The fact that the misclassification affected both cases and controls indicates a nondifferential misclassification, which dilutes the association between A and B. 3. Investigators think that income might be a confounder in the relationship between Hispanic ethnicity and cardiovascular disease. They conduct a case-control study, and they match cases and controls based on income. They find that Hispanics are more likely to have cardiovascular disease as compared with non-Hispanics. What is the measure of association used in such study? a. Risk ratio b. Relative risk c. Incidence rate ratio

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d. Attack rate e. Odds ratio ANS: E Odds ratio is the proper measure of association used in case-control study.

4. Investigators think that income might be a confounder in the relationship between Hispanic ethnicity and cardiovascular disease. They conduct a case-control study and they match cases and controls based on income. They find that Hispanics are more likely to have cardiovascular disease as compared with non-Hispanics. What would you conclude about income as a potential confounder in this association? a. Income is a confounder. b. Income is not a confounder. c. Income is an effect modifier. d. Income is not associated with cardiovascular disease. e. Income is not associated with ethnicity.

ANS: B In a case-control study, if, after matching for a potential confounder, we still find an association between the exposure and the outcome, we can say that the potential confounder is actually not a confounder.

5. This table shows incidence rateN s (UpR erS1I 00N,0G0T 0)Bo. fC grO ouMps exposed to neither risk factors or to one or two risk factors for lung cancer. What is the expected value of incidence rate X on asbestos exposure group among smokers in additive scale?

Incidence Rates of Lung Cancer by Asbestos and Smoking Exposure Status Smoking status

Asbestos exposure

No

Yes

No

2.0

6.0

Yes

4.0

X

a. 4.0 b. 6.0 c. 8.0 d. 12.0 e. 24.0 ANS: C Among nonsmokers, asbestos exposure increased the incidence rate of lung cancer 2 cases per 100,000 (4 − 2) in additive scale. Simply applying that additive effect to the next column,

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smokers, we can expect to observe 8 cases per 100,000 (6 + 2) among asbestos-exposed smokers in additive scale.

6. This table shows incidence rates (per 100,000) of groups exposed to neither risk factors or to one or two risk factors for lung cancer. What is the expected value of incidence rate X on asbestos exposure group among smokers in multiplicative scale?

Incidence Rates of Lung Cancer by Asbestos and Smoking Exposure Status Smoking status

Asbestos exposure

No

Yes

No

2.0

6.0

Yes

4.0

X

a. 4.0 b. 6.0 c. 8.0 d. 12.0 e. 24.0 ANS: D Among nonsmokers, asbestos expN osUuR reSinIcN reG asT edBt. heCiO ncMidence rate of lung cancer 2 times (4/2) in multiplicative scale. Simply applying that multiplicative effect to the next column, smokers, we can expect to observe 12 cases per 100,000 (6 × 2) among asbestos-exposed smokers in multiplicative scale.

7. Epidemiologists tried to investigate the role of factor Y in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor Y. In this analysis, what is the odds ratio in the overall population?

Overall Case

Control

Exposed

1,000

500

Unexposed

200

500

Case

Control

Exposed

800

250

Unexposed

100

250

Factor Y present

Factor Y absent

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Case

Control

Exposed

200

250

Unexposed

100

250

a. 0.5 b. 1.0 c. 2.0 d. 5.0 e. 8.0 ANS: D Using the information from the table, the odds ratio can be easily calculated and equals the odds of exposure among the cases (1,000/200) divided by the odds of exposure among the controls (500/500). This ratio equals 5.

8. Epidemiologists tried to investigate the role of factor Y in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor Y. Based on the information given, what is the role of factor Y in the exposure-disease relationship?

Overall Case

Control

Exposed

1,000

500

Unexposed

200

500

Case

Control

Exposed

800

250

Unexposed

100

250

Case

Control

Exposed

200

250

Unexposed

100

250

Factor Y present

Factor Y absent

a. Factor Y is a confounder. b. Factor Y is an effect measure modifier. c. Factor Y is a mediator. d. Factor Y is an outcome. e. Factor Y does not have any role in the exposure-disease relationship.

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ANS: B In the overall table, the odds ratio equals the odds of exposure among the cases (1,000/200) divided by the odds of exposure among the controls (500/500). The ratio in overall equals 5.

In the table when Y is present, the odds ratio equals the odds of exposure among the cases (800/100) divided by the odds of exposure among the controls (250/250). This ratio in overall equals 8. In the table when Y is absent, the odds ratio equals the odds of exposure among the cases (200/100) divided by the odds of exposure among the controls (250/250). This ratio in overall equals 2. The odds ratios of exposure vary by the presence of factor Y, and the overall odds ratio is also different from stratified odds ratios. This association indicates that factor Y is an effect measure modifier which changes the effect of exposure to the outcome by its status.

9. Epidemiologists tried to investigate the role of factor X in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor X. Based on the information given, what is the role of factor X in the exposure-disease relationship?

Overall Case

Control

Exposed

1,050

500

Unexposed

300

700

Case

Control

Exposed

700

250

Unexposed

200

350

Case

Control

Exposed

350

250

Unexposed

100

350

Factor X present

Factor X absent

a. Factor X is a confounder. b. Factor X is an effect measure modifier. c. Factor X is a mediator. d. Factor X is an outcome. e. Factor X does not have any role in the exposure-disease relationship.

ANS: E In the overall table, the odds ratio equals the odds of exposure among the cases (1,050/300) divided by the odds of exposure among the controls (500/700). The ratio in overall equals

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4.9. In the table when X is present, the odds ratio equals the odds of exposure among the cases (700/200) divided by the odds of exposure among the controls (250/350). This ratio in overall equals 4.9. In the table when X is absent, the odds ratio equals the odds of exposure among the cases (350/100) divided by the odds of exposure among the controls (250/350).

This ratio in overall equals 4.9. The odds ratios of exposure do not vary by the presence of factor X, and the overall odds ratio is same as stratified odds ratios. This association indicates that factor X does not have any role in the relationship between exposure and outcome.

10. Epidemiologists tried to investigate the role of factor Z in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor Z. Based on the information given, what is the role of factor Z in the exposure-disease relationship?

Overall Case

Control

Exposed

200

160

Unexposed

200

240

Case

Control

Exposed

20

90

Unexposed

8N0

210

Case

Control

Exposed

180

70

Unexposed

120

30

Factor Z present

U

Factor Z absent

a. Factor Z is a confounder. b. Factor Z is an effect measure modifier. c. Factor Z is a mediator. d. Factor Z is an outcome. e. Factor Z does not have any role in the exposure-disease relationship.

ANS: A In the overall table, the odds ratio equals the odds of exposure among the cases (200/200) divided by the odds of exposure among the controls (160/240). The ratio in overall equals 1.5. In the table when Z is present, the odds ratio equals the odds of exposure among the cases (20/80) divided by the odds of exposure among the controls (90/210). This ratio in overall equals 0.58. In the table when Z is absent, the odds ratio equals the odds of exposure among the cases (180/120) divided by the odds of exposure among the controls (70/30). This ratio in overall equals 0.64. The odds ratios of exposure do not vary by the presence of factor

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Z, but the overall odds ratio is not the same as stratified odds ratios. This association indicates that factor Z is a confounder in the relationship between exposure and outcome.

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Chapter 16: Identifying the Roles of Genetic and Environmental Factors in Disease Causation Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. The following suggests environmental factors causing a disease: a. Monozygotic twins getting the same disease b. Family history of disease c. Early development d. A rapid change in the trends of disease over time e. Biologic brothers adopted by different families getting the same disease ANS: D Changes in the trends in short periods suggest environmental factors in the causation of disease.

The other options suggest genetic factors in the causation of disease.

2. Huntington disease is an autosomal dominant disease. It is characterized by the adult onset of abnormal movements, cognitive imN paU irR mS enIt,NaG ndT, B of. teC n,OpM sychiatric symptoms. For its type of transmission pattern (autosomal dominant) it is considered a a. complex genetic disease. b. multiple gene disease. c. environmental disease. d. vector borne. e. Mendelian disease.

ANS: E Mendelian diseases are characterized for being mutations in single genes affecting either autosomal or sexual chromosomes, and being either dominant or recessive. Such information is enough to answer this question because the sentence indicates that Huntington is an autosomal dominant disease.

3. A total of 1,500 pairs of adult twins, 600 monozygotic and 900 dizygotic, were studied to estimate the concordance for a childhood cancer. In the 600 monozygotic twins, 40 of the pairs were concordant for the disease, 60 of the pairs were discordant for the disease, and neither twin had the disease in the remaining 500 pairs. In the 900 dizygotic twins, 30 of the pairs were concordant for the disease, 120 of the pairs were discordant for the disease, and neither twin had the disease in the remaining 750 pairs. What is the concordant rate, in monozygotic twins, of the disease in twin pairs with at least one affected member?

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a. 0.1 b. 0.4 c. 0.6 d. 0.7 e. 1.5 ANS: B The concordant rate of the disease in twin pairs with at least one affected member among monozygotic twins is 40, the number of pairs with concordant, divided by 100, 40 plus 60, the total number of pairs with at least one affected member. The concordant rate equals 0.4.

4. A total of 1,500 pairs of adult twins, 600 monozygotic and 900 dizygotic, were studied to estimate the concordance for a childhood cancer. In the 600 monozygotic twins, 40 of the pairs were concordant for the disease, 60 of the pairs were discordant for the disease, and neither twin had the disease in the remaining 500 pairs. In the 900 dizygotic twins, 30 of the pairs were concordant for the disease, 120 of the pairs were discordant for the disease, and neither twin had the disease in the remaining 750 pairs. What is the discordance rate, in dizygotic twins, of the disease in twin pairs with at least one affected member? a. 0.1 b. 0.2 c. 0.6 d. 0.8 e. 1.5 ANS: B The discordance rate of the disease in twin pairs with at least one affected member among of dizygotic twins is 30, the number of pairs with concordant, divided by 150, 30 plus 120, the total number of pairs with at least one affected member. The discordance rate equals 0.2.

5. A total of 1,500 pairs of adult twins, 600 monozygotic and 900 dizygotic, were studied to estimate the concordance for a childhood cancer. In the 600 monozygotic twins, 40 of the pairs were concordant for the disease, 60 of the pairs were discordant for the disease, and neither twin had the disease in the remaining 500 pairs. In the 900 dizygotic twins, 30 of the pairs were concordant for the disease, 120 of the pairs were discordant for the disease, and neither twin had the disease in the remaining 750 pairs. What is the most reasonable conclusion to be drawn from these data? a. Genetic factors are unimportant in the etiology of childhood cancer. b. The data suggest a potentially important genetic component. c. The incidence of childhood cancer within monozygotic twins is higher than dizygotic twins. d. The prevalence of childhood cancer within dizygotic twins is higher than monozygotic twins. e. Environmental factors are the major determinants of child food cancer.

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ANS: B The concordant rate of the disease in twin pairs with at least one affected member among monozygotic twins is 0.4, 40 divided by 100. And the concordant rate of the disease in twin pairs with at least one affected member among dizygotic twins is 0.2, 30 divided by 150. The concordance rate is higher in monozygotic twins than in dizygotic twins, which indicates that there is some role of genetic factors in childhood cancer. “Genetic factors are unimportant in the etiology of childhood cancer” is not correct, because data suggest that genetic factors are important in the etiology of childhood cancer. “The incidence of childhood cancer within monozygotic twins is higher than dizygotic twins” and “The prevalence of childhood cancer within dizygotic twins is higher than monozygotic twins” are not correct. Based on given information, we cannot calculate and compare the incidence rate or prevalence of childhood cancer. “Environmental factors are the major determinants of child food cancer” is not correct. It is hard to say that environmental factors are the major determinants of childhood cancer.

6. In a study of Korean migrants to the United States, the following standardized mortality ratios (SMRs) were found for disease X. What is the most reasonable conclusion to be drawn from these data? Use the table below to answer the question.

Standardized Mortality Ratios by Migrant History Group

SMR

Native Korean living in Korea

219

Korean migrants who left the country at age >30

214

Korean migrants who left the country at age <15

115

Children of Korean ancestry

109

United States whites

104

a. Environmental factors are unimportant in the etiology of disease X. b. The data suggest potentially important genetic components. c. Environmental factors exposed between age 15 and 30 are associated with disease X. d. Migrants are highly representative of the population in their native country. e. Age at the migration is not related with disease X. ANS: C Korean migrants who left the country at age younger than 15 have relatively lower SMR compared with Korean migrants who left the country at age older than 30 and native Korean living in Korea. This indicates that environmental factors to which people are exposed at ages between 15 and 30 have an effect on disease X SMR. “Environmental factors are unimportant in the etiology of disease X” is not correct. If environmental factors were not unimportant, SMR

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will not be changed by immigrant status. “The data suggest potentially important genetic components” is not correct. If genetic components were important factors, SMR in children of Korean ancestry will be high. “Migrants are highly representative of the population in their native country” is not correct. Migrants cannot be representative of the population from the country. “Age at the migration is not related with disease X” is not correct. Age at migration shows a major role for SMR in this study.

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Chapter 17: Using Epidemiology to Evaluate Health Services Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which of the following statements is the most accurate definition of efficacy? a. Testing a drug in a group of participants who have agreed to join clinical trial. b. A measure of a specific intervention, procedure, regimen, or service, when deployed in the usual circumstances of living and practice. c. Testing a new drug in a community where individuals have various compliances of drug intake. d. Estimating the cost-benefit ratio based on agent effectiveness. e. The effects or end results achieved in relation to the effort expended in terms of money, resources, and time.

ANS: A Measuring the effect of intervention, procedures, regiment, or service in ideal setting is an example of efficacy. “A measure of a specific intervention, procedure, regimen, or service, when deployed in the usual circumstances of living and practice” and “Testing a new drug in a community where individuals have various compliances of drug intake” are not correct.

NUatin RSgIthNeGcT B.CO Those indicate effectiveness. “Estim ost-ben efitMratio based on agent effectiveness” and “The effects or end results achieved in relation to the effort expended in terms of money, resources, and time” are not correct. Those indicate efficiency.

2. Which of the following statements is the most accurate definition of effectiveness? a. Testing a vaccine in a group of consenting individuals. b. A measure of a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions. c. Testing a vaccine in a community where some of individuals do not want to be vaccinated. d. The process of making the best use of scarce resources. e. The effects or end results achieved in relation to the effort expended in terms of money, resources, and time.

ANS: C Measuring the effect of intervention, procedures, regiment, or service in the real world is an example of effectiveness. “Testing a vaccine in a group of consenting individuals” and “A measure of a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions” are not correct. Those indicate efficacy. “The process of making the best use of scarce resources” and “The effects or end results achieved in relation to the effort expended in terms of money, resources, and time” are not correct. Those indicate efficiency.

3. Which of the following statements is the most accurate definition of efficiency?

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a. A measure of a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions. b. The process of testing a vaccine in a community where some of individuals do not want to be vaccinated. c. The process of testing a new drug in a community where individuals have various compliances of drug intake. d. The process of estimating the best effort of intervention or procedure. e. The effects or end results achieved in relation to the effort expended in terms of money, resources, and time.

ANS: E Efficiency is more like a measure or comparison of effects of agents related to the money, emotions, pain, time, absenteeism, social stigma, and disability. “A measure of a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions” and “The process of estimating the best effort of intervention or procedure” are not correct. Those indicate efficacy. “The process of testing a vaccine in a community where some of individuals do not want to be vaccinated” and “The process of testing a new drug in a community where individuals have various compliances of drug intake” are not correct.

Those indicate effectiveness.

4. When testing whether we can achieve a less expensive and better way to treat a disease with an intervention that has shown to work previously, we are looking for a. efficacy. b. effectiveness. c. efficiency. d. power. e. feasibility.

ANS: C Efficiency evaluates if effective treatments can achieve a less expensive and better way to work. The cost-benefit ratio is assessed where cost includes money, discomfort, pain, absenteeism, disability, and social stigma.

5. In general terms, a health indicator is a a. rare disease that reflects how the system deals with complex conditions. b. sentinel condition that is assumed to reflect the general level of health care. c. disease that reflects infant health. d. disease that reflects maternal and child health. e. statistical test used to compare the health situation of two countries.

ANS: B A health indicator is a sentinel conditions that is thought to reflect the general level of health care for a specific region.

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6. The government of Country A decided to introduce a new treatment strategy for disease X. It was decided that, starting in January 1, 2019, all patients diagnosed with disease X in public hospitals would receive the new treatment. Researchers were asked to evaluate the new treatment. Which of the following designs is the best approach to evaluate the new treatment? a. Randomized clinical trial b. Case-control study c. Cross-sectional survey d. Before-after study e. Case-series ANS: D Before-after studies are helpful to evaluate a new treatment when randomization is not feasible and there is a clear date when the new treatment was established, such as in this example (January 1, 2019).

7. According to the healthy people 2020, the following is an indicator of access to health services: a. Persons with a usual primary care provider b. Persons with a diagnosed diabetes whose A1c is greater than 9% c. Adolescents with a major depressive episode in the past 12 months d. Knowledge of serostatus among human immunodeficiency virus (HIV)-positive persons e. Adult cigarette smoking ANS: A “Persons with a diagnosed diabetes whose A1c is greater than 9%” is an indicator of clinical preventive services, “Adolescents with a major depressive episode in the past 12 months” is an indicator of mental health, “Knowledge of serostatus among human immunodeficiency virus (HIV)-positive persons” is an indicator of reproductive and sexual health, and “Adult cigarette smoking” is an indicator of tobacco use.

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Chapter 18: Epidemiologic Approach to Evaluating Screening Programs Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which of the following statements is the most accurate example of primary prevention? a. Promoting antismoking campaign in the community b. Taking low-dose computed tomography scan to detect the early stage of lung cancer c. Quitting smoking after diagnosis of chronic obstructive pulmonary disease d. Removal of malignant lung cancer to reduce the pain from tumor e. Participating in cancer rehabilitation programs in primary health care center after surgery ANS: A Primary prevention is a behavior to prevent the disease or eliminating risk factors when the disease is not occurred. “Taking low-dose computed tomography scan to detect the early stage of lung cancer” and “Quitting smoking after diagnosis of chronic obstructive pulmonary disease” are not correct. Those are secondary prevention. “Removal of malignant lung cancer to reduce the pain from tumor” and “Participating in cancer rehabilitation programs in N R” I G t B.C M primary health care center after surgUeryS arN e noT correct. Those are tertiary prevention.

2. Which of the following statements is the most accurate example of secondary prevention? a. Providing human papillomavirus (HPV) vaccines to kids who are 11 or 12 years of age b. Using condoms to prevent sexually transmitted disease c. Taking a routine Pap smear test d. Receiving a hysterectomy after diagnosis of cervical cancer e. Participating in rehabilitation programs to reduce the pain after surgery ANS: C Secondary prevention is a behavior to detect the disease as early as possible. “Providing human papillomavirus (HPV) vaccines to kids who are 11 or 12 years of age” and “Using condoms to prevent sexually transmitted disease” are not correct. Those are primary prevention. “Receiving a hysterectomy after diagnosis of cervical cancer” and “Participating in rehabilitation programs to reduce the pain after surgery” are not correct. Those are tertiary prevention.

3. Which of the following statements is the most accurate example of tertiary prevention? a. Receiving a yellow fever vaccination at a tertiary hospital

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b. Using a mosquito net while visiting a malaria-endemic country c. Taking preventative malaria drug before getting an infection d. Receiving regular blood smear test to detect the malaria early e. Joining malaria rehabilitation programs to reduce or eliminate long-term impairments and disabilities from previous infections ANS: E Tertiary prevention is a kind of behavior to reduce or eliminate the impact of long-term disease. “Receiving a yellow fever vaccination at a tertiary hospital,” “Using a mosquito net while visiting a malaria-endemic country,” and “Taking preventative malaria drug before getting an infection” are not correct. Those are primary prevention. “Receiving regular blood smear test to detect the malaria early” is not correct. This is secondary prevention.

4. Epidemiologists decided to investigate the validity of new diagnostic tool for breast cancer.

They used this new diagnostic tool for breast cancer in 150 women with biopsy-proven breast cancer in 300 age- and race-matched control women. The results of the new tool were positive in 136 cases and in 35 control women, all of whom showed no evidence of cancer at biopsy. What is the sensitivity of new diagnosis tool for breast cancer? a. 9% b. 12% c. 33% d. 91% e. 88% ANS: D The sensitivity of the new diagnostic test is the number of positive cases among cases divided by the number of total cases, which equals 136 divided by 150. The sensitivity is 91%.

5. Epidemiologists decided to investigate the validity of new diagnostic tool for breast cancer.

They used this new diagnostic tool for breast cancer in 150 women with biopsy-proven breast cancer in 300 age- and race-matched control women. The results of the new tool were positive in 136 cases and in 35 control women, all of whom showed no evidence of cancer at biopsy. Now, the epidemiologists want to use the new diagnostic tool for screening program in Cities A and B. Based on previous cross-sectional studies, the prevalence of breast cancer is 5% in City A and 1% in City B. What is the expected positive predictive value of new diagnosis tool for breast cancer in City A? a. 30% b. 43% c. 81% d. 89%

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e. 91% ANS: A The sensitivity of new diagnostic test is 91%, from 136 divided by 150. The specificity of new diagnostic test is 89%, from 265 divided by 300. The prevalence of breast cancer in City A is 5%. Let us assume we have 100,000 people in City A; 5,000 individuals have breast cancer, and 95,000 individuals do not have breast cancer. The total number of people who test positive by the new diagnostic test equals the number of people who test positive from people who have cancer plus the number of people who test positive from people who do not have cancer. The number of people who test positive from people who have cancer equals 4,550 (5,000 multiplied by 0.91; the sensitivity). The number of people who test positive from people who do not have cancer equals 10,450 (95,000 multiplied by 0.11; 1 minus the specificity). The number of people who test positive by the new diagnostic test is 15,000.

Therefore the positive predictive value is 0.30 (equals 4,550 divided by 15,000).

6. Epidemiologists decided to investigate the validity of new diagnostic tool for breast cancer.

They used this new diagnostic tool for breast cancer in 150 women with biopsy-proven breast cancer in 300 age- and race-matched control women. The results of the new tool were positive in 136 cases and in 35 control women, all of whom showed no evidence of cancer at biopsy. Now, the epidemiologists want to use the new diagnostic tool for screening program in Cities A and B. Based on previous cross-sectional studies, the prevalence of breast cancer RSt I GT Uha is 5% in City A and 1% in City B.NW is N the mB.C ost reO asonable conclusion to be drawn from these data? a. Positive predictive value of new diagnostic tool for breast cancer in City A is higher than expected positive predictive value in City B. b. Positive predictive values will be higher than sensitivity. c. Positive predictive value is affected by the specificity of the test only. d. Prevalence will not affect the positive predictive value. e. Positive predictive value is a fixed characteristic of the test. Therefore the positive predictive value in City A will be same as positive predictive value in City B. ANS: A The sensitivity of new diagnostic test is 91%, from 136 divided by 150. The specificity of new diagnostic test is 89%, from 265 divided by 300. The positive predictive value is the number of people who test positive from people who have cancer divided by total number of people who test positive from people who have cancer and people who do not have cancer, which equals sensitivity multiplied by prevalence divided by addition of sensitivity multiplied by prevalence and 1 minus specificity multiplied by 1 minus prevalence. Therefore the positive predictive value of the test in City A is 0.30, which equals 0.05 multiplied by 0.91 divided by addition of 0.05 multiple 0.91 and 0.11 multiplied by 0.95. The positive predictive value of the test in City A is 0.01, which equals 0.01 multiplied by 0.91 divided by

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addition of 0.01 multiplied by 0.91 and 0.11 multiplied by 0.99. “Positive predictive values will be higher than sensitivity” is not correct. Positive predictive values are lower than sensitivity. “Positive predictive value is affected by the specificity of the test only” and “Prevalence will not affect the positive predictive value” are not correct. Positive predictive values are affected by sensitivity, specificity, and prevalence. “Positive predictive value is a fixed characteristic of the test. Therefore the positive predictive value in City A will be same as positive predictive value in City B” is not correct; positive predictive value is not a fixed characteristic of the test.

7. Which of the following statements is not an accurate description of epidemiologic studies using large group data such as National Hospital Discharge Survey or National Health Interview Survey? a. The advantage of using large data sets is that the data refer to real-world populations; the issue of representativeness is minimized. b. Because the data sets exist at the time the research is initiated, analysis can be completed and results generated relatively rapidly. c. Given the large data sets used, sample size is usually considered a major problem. d. Data are usually gathered for fiscal and administrative purposes; they may not be well suited for scientific research. e. When necessary variables or questions are absent, the investigators may consciously or subconsciously change the research questions.

N R I G

ANS: C Because the large data sets used have large participants in the study, sample size is usually not considered as a problem except in a subgroup analysis. “The advantage of using large data sets is that the data refer to real-world populations; the issue of representativeness is minimized” and “Because the data sets exist at the time the research is initiated, analysis can be completed and results generated relatively rapidly” are correct explanations. Those are advantages of using large group data in epidemiologic studies. “Data are usually gathered for fiscal and administrative purposes; they may not be well suited for scientific research” and “When necessary variables or questions are absent, the investigators may consciously or subconsciously change the research questions” are correct explanations. However, those explanations are disadvantages of using large group data.

8. In the model of the Natural History of Disease, the period of time between the onset of signs and symptoms of disease and its ultimate outcome (cure, control, or death) is known as a. preclinical phase. b. clinical phase. c. clinical horizon. d. incubation period. e. latent period.

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ANS: B In the model of Natural History of Disease, there are two phases once the disease is present.

The preclinical phase is the time when disease is present but has not manifested clinically (no signs or symptoms) and it ends with the onset of symptoms and signs. The clinical phase starts with the onset of symptoms and signs and ends with the ultimate outcome of the disease (cure, control, or death).

9. In the model of the Natural History of Disease, when is the ideal time to do screening for a disease? a. Preclinical phase b. Clinical phase c. Clinical horizon d. Before disease starts e. Latent period ANS: A The best time for a screening program is the preclinical phase. In such phase, the disease is present but has not manifested clinically and therefore is typically not diagnosed. The NanReSarly INdia GTgnosis.

B.CO M screening program would allow for U 10. The usual time to death after diagnosis of disease X is 2 years. A screening program allows for the early detection of disease X, on average 1 year earlier than the usual diagnosis; however, there is no available treatment even in early stages of disease X. With the screening program it seems like the time to death has increased to 3 years; however, this is only due to the early diagnosis thanks to the screening program. What is the name of the issue previously described? a. Timing bias b. Survival bias c. Selection bias d. Confounding e. Lead-time bias ANS: E Lead-time bias describes the false, seemingly increased survival due to an early diagnosis with no delay in the time of death.

11. The following is a reason for an apparent lack of benefit from a screening program:

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a. The available treatments are not effective even when administered early in the disease progression. b. The clinical phase of disease is long and usually ends with the death of the patient. c. The usual diagnosis of disease happens very late in the disease progression. d. The preclinical phase of disease is very long. e. The current therapies are very effective when administered in the preclinical phase of disease.

ANS: A Screening programs will be effective only when the available treatments are more effective when administered in the preclinical or early stages in the disease progression.

12. A recent study found that screening for disease X led to increased survival. In the study, those who were screened were generally younger, healthier, and more aware of their health than those who were not screened. This makes it hard to evaluate whether the improvement in survivorship was due to the screening program or due to the characteristics of those who are screened. What is the name of this issue when evaluating the effect of a screening program? a. Lead time bias b. Overdiagnosis bias c. Selection bias d. Misclassification bias e. Length-biased sampling ANS: C Selection bias is an important issue to consider when evaluating the effectiveness of screening programs. Usually, participants of a screening program are healthier than the general population, and therefore it becomes hard to assess whether the screening program was effective or whether the characteristics of those who participate in it make it seem effective.

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Chapter 19: Epidemiology and Public Policy Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. Which of the following statements is not an accurate description of epidemiology in health policy? a. A major role of epidemiology is a basis for developing policies that may affect human health. b. One of the roles of epidemiology in public health policy is for risk assessment. c. Some researchers use systematic review or meta-analysis to synthesize the literature regarding a specific health topic. d. Epidemiology is the only relevant scientific discipline in the process of risk assessment. e. Journals that may not want to publish the studies report no association will increase the publication bias.

ANS: D Epidemiology is not the only relevant scientific discipline; for example, toxicology also is a relevant scientific discipline in the process of risk assessment. However, epidemiologic data are essential in each of the processes, nN otUoR nlS yI inNthGeTpB ro. ceCsO s oMf risk assessment. “A major role of epidemiology is a basis for developing policies that may affect human health,” “One of the roles of epidemiology in public health policy is for risk assessment,” “Some researchers use systematic review or meta-analysis to synthesize the literature regarding a specific health topic,” and “Journals that may not want to publish the studies report no association will increase the publication bias” are accurate explanations of epidemiology in health policy.

2. The same epidemiologic question regarding the effectiveness of a treatment can be addressed by several studies. Often, there are inconsistencies between such studies. What can be done when such discrepancies are found? a. Trust the study done by senior researchers. b. Trust the study with bigger sample size. c. Conduct a systematic review with a meta-analysis. d. Trust the study that makes more sense. e. None of the previous.

ANS: C Systematic reviews with meta-analyses allow for the integration of multiple findings, and metaanalyses help to aggregate the results from a set of studies to provide a comprehensive answer to an epidemiologic question.

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3. What is the name of the chart that is typically used to depict the results of a meta-analysis? a. Forest plot b. Pie chart c. Box plot d. Manhattan plot e. Bar chart ANS: A Forest plots are typically used to represent the results of meta-analysis. The rest of the options describe other charts used in epidemiology but not typically in meta-analysis.

4. When decision makers are in the process of assessing whether a new policy should be implemented to avoid a certain health risk, besides considering the scientific evidence available, they should also take into account the following societal consideration: a. If that decision would make them look good with constituents b. The proportion of the population would be protected by such policy c. If that new policy was proposed by prestigious academics d. The media’s opinion about the policy e. The incidence rate of the disease ANS: B The societal issues that should be considered when deciding about a new policy include the proportion of the population protected by that policy, costs, and willingness of the population to adopt that policy, among others. None of the other options is a societal issue that should be considered.

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Chapter 20: Ethical and Professional Issues in Epidemiology Celentano: Gordis Epidemiology, 6th Edition MULTIPLE CHOICE 1. One difference between epidemiology and other scientific disciplines, regarding the impact of their findings, is that a. epidemiologic findings are not prone to falsification. b. epidemiology is the only science that deals with humans. c. epidemiologic findings have immediate policy implications for clinical practice and public health. d. epidemiologic findings are not prone to misinterpretations. e. epidemiologic findings are the easiest to understand.

ANS: C Historically, epidemiologic findings have immediate implications for clinical practice and public health. The removal of the handle of the Broad Street pump in an effort to control a cholera outbreak is an example of that. Moreover, epidemiology, as any other scientific discipline, is prone to falsification and misinterprN etU atR ioS nI ; tN heG reTfoBre.“CeO piM demiologic findings are not prone to falsification” and “epidemiologic findings are not prone to misinterpretations” are incorrect.

2. What of the following is an obligation that researchers have with study participants? a. Provide a financial incentive to participate in the study. b. Provide free treatment for any condition the subjects have. c. Communicate the study results clearly. d. Enroll all family members of the participants if they want to be part of the study. e. Provide free diagnostic procedures, even if those are not related with the study.

ANS: C Researchers must communicate clearly with the participants the results of the study, including the identification of potential health risks that are found as part of the study. For example, if as part of the study it is found that exposure to A is associated with disease D, researchers must inform all participants exposed to A that they are at increased risk of D. 3. To abide with the ethical principle of autonomy, epidemiologic research requires a. epidemiologists to provide financial incentives. b. to obtain participant’s consent before collecting any information. c. to investigate only participants who are in excellent health.

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d. share participant’s information with any institution. e. that only one researcher is able to access the data collected.

ANS: B The ethical principle of autonomy argues for the informed consent of participants before the formal investigation begins.

4. A challenge in epidemiologic research that explores the effect of race on cardiovascular disease is that a. measuring race is hard because is a poorly understood concept and its validity is questionable. b. measuring race requires DNA testing. c. there are too many human races. d. race is usually not associated with health outcomes. e. cardiovascular disease is not well defined.

ANS: A Race is a poorly understood concepts and its biologic validity is questionable. Race is often used to characterize individuals, but there is no biologic evidence of different human races. However, this construct is associated with health outcomes, potentially for socioeconomic differences between subjects characterized into different races.