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SPECIAL REPORT

Capillary Blood Sampling – Achieving the Perfect Sample Capillary Blood Sampling – Achieving the Perfect Sample Blood Tests from Needle to Pin-Prick with Caution The Point to Point of Care Testing Antigen and Antibody Tests That Can Save Lives and Resources Reliable Micro Fluid Results

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

SPECIAL REPORT

Capillary Blood Sampling – Achieving the Perfect Sample Capillary Blood Sampling – Achieving the Perfect Sample Blood Tests from Needle to Pin-Prick with Caution

Contents

The Point to Point of Care Testing Antigen and Antibody Tests That Can Save Lives and Resources Reliable Micro Fluid Results

Foreword

2

Dr Charles Easmon, Editor

Capillary Blood Sampling – 3 Achieving the Perfect Sample Faye Murray, Junior Product Manager at Owen Mumford Ltd Sponsored by

Published by Global Business Media

Published by Global Business Media Global Business Media Limited 62 The Street Ashtead Surrey KT21 1AT United Kingdom Switchboard: +44 (0)1737 850 939 Fax: +44 (0)1737 851 952 Email: info@globalbusinessmedia.org Website: www.globalbusinessmedia.org Publisher Kevin Bell Business Development Director Marie-Anne Brooks Editor Dr Charles Easmon Senior Project Manager Steve Banks Advertising Executives Michael McCarthy Abigail Coombes Production Manager Paul Davies For further information visit: www.globalbusinessmedia.org

The opinions and views expressed in the editorial content in this publication are those of the authors alone and do not necessarily represent the views of any organisation with which they may be associated. Material in advertisements and promotional features may be considered to represent the views of the advertisers and promoters. The views and opinions expressed in this publication do not necessarily express the views of the Publishers or the Editor. While every care has been taken in the preparation of this publication, neither the Publishers nor the Editor are responsible for such opinions and views or for any inaccuracies in the articles.

Introduction The Trend Towards Increased Point of Care Testing Two Safety Lancet Types Practical Considerations for Capillary Blood Sampling How to Obtain a Capillary Blood Sample Owen Mumford’s Unistik Range of Safety Lancets

Blood Tests from Needle to Pin-Prick with Caution

7

Joanna Hastings, Medical Correspondent

The Value of Near Patient Testing (Point Of Care) A Cautionary Tale of Devices and Dreams What Theranos Offered Summary

The Point to Point of Care Testing

9

Dr Charles Easmon, Editor

The Professional Perspective The Patient Perspective Summary

Antigen and Antibody Tests That 11 Can Save Lives and Resources Joanna Hastings, Medical Correspondent

Pinprick Tests that can Save Lives and Resources Care with Antibiotics Summary

Reliable Micro Fluid Results

13

Dr Charles Easmon, Editor

Negative or Positive (or Interesting?) The Range of a Blood or Micro Fluid Result Summary

© 2016. The entire contents of this publication are protected by copyright. Full details are available from the Publishers. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical photocopying, recording or otherwise, without the prior permission of the copyright owner.

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

Foreword A

NY DEDICATED and determined craftsperson

(the classic line) help make test results ‘instant’ or as

uses the best tools for their job. To get blood

close to instant as possible.

from a fingertip or a heel requires a device well-

Sadly, leaving medical school does not mean leaving

designed and safety tested that has a low risk of

statistics behind and at least a basic understanding

personal injury, cross-infection or pain/discomfort

of what a test result means or could mean in any

to the tester and the tested. Fortunately, such

given circumstances or environment is essential if the

devices are available1.

tools used are not to be wasted or wrongly applied

The ‘sample’ then needs to be interpreted in a

or interpreted.

device that is reliable and consistent. The ideal device

It is a waste of your time and your patient’s time

is regularly calibrated and has known reference

if the tools you use to take blood or micro fluids do

ranges or an acceptable level of true positives as well

not generate the required amount of blood or micro

as true negatives .

fluid to make the test possible and it becomes unkind

2

Point of care testing3 is an exciting and rapidly

to have to pin prick the individual more than once.

advancing area of medicine but cost-effectiveness

An effective lancet that does the job should ideally

and cost-efficiency assessments should always be

be used from the start and then disposed of safely.

taken where possible. Equipment must be bought and

Your patients will be grateful that you and your team

maintained. Staff must be trained how to use it and

chose the right tools and you will find a higher level

associated devices accurately. In the UK, advice and

of satisfaction about a job well done rather than the

training for the taking of blood is available from The

frustration of having to start all over again and waste

National Association of Phlebotomists .

valuable resources and time.

4

Testing requires an understanding of antigens and antibodies and how the two interact. Clever tools that make the interaction visible to the naked eye

Dr Charles Easmon Editor

Dr Charlie Easmon is a medical doctor with 30 years’ experience in the public and private sectors. After qualifying as a physician, he developed his interests in occupational medicine, public health and travel diseases. His interest in liver disease is from both the public health point of view as recommended by the Hepatitis C Trust/The Lancet Commission on Liver Disease and the occupational health point of view.

References: www.owenmumford.com Accessed 8/6/2016

1 2

http://labtestsonline.org.uk/ Accessed 8/6/2016

3

http://orion.bme.columbia.edu/~sia/Sam_LOC_b817915h.pdf

4

Accessed 8/6/2016 http://www.phlebotomy.org/home Accessed 8/6/2016

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

Capillary Blood Sampling – Achieving the Perfect Sample Faye Murray, Junior Product Manager at Owen Mumford Ltd A review of best clinical practice for capillary blood sampling using safety lancet devices.

Introduction Capillary blood sampling is a method used for obtaining relatively small blood samples that requires puncturing the dermal layer of the skin to access the tiny capillaries closest to the surface. It is becoming increasingly common in healthcare settings, as an alternative to laboratory testing, for Point of Care (POC) diagnostic testing. In many countries, safety lancets have now become the routine device used by healthcare professionals to obtain a capillary blood sample. Safety lancets contain a mechanism that causes/ allows the needle to automatically retract into the body of the device following skin penetration, and cannot be re-used. This protects healthcare professionals from needle stick injuries and patients from cross-infection. Safety lancets vary according to type, needle gauge and needle length. Determining which lancet to use will depend upon the patient, the diagnostic test for which the sample is required and consideration of pain reduction. The latter factor is especially important for patients from whom samples must be collected repeatedly. This article provides a guide to choosing the most appropriate safety lancet, and how to obtain the optimum capillary blood sample for the POC test at hand.

The Trend Towards Increased Point of Care Testing Blood glucose testing is the most commonly conducted POC test, and is forecast to account for over 40% of the global market by 20181. Other commonly performed POC tests include blood coagulation tests, whose use is growing rapidly in the emergency and critical care contexts2. The testing of rapid cardiac markers is the fastest growing of all the POC applications1, largely driven by clinical evidence of the advantages of POC testing patients with

acute coronary syndrome (ACS) over traditional laboratory testing2. More generally, the trend towards increased POC testing is being influenced by the benefits of bringing tests closer to the patient for immediate results and faster diagnosis, and by advances in diagnostic devices and technology.

Two Safety Lancet Types Contemporary safety lancets are available in two broad types – puncture blade and motion blade variants. Puncture blade safety lancets (Figure 1, overleaf) are generally used for finger sampling and operate by penetrating the skin in an up-and-down motion, to a range of safe, pre-determined depths. Motion blade, or arched blade, safety lancet devices (Figure 2, overleaf) are often used to obtain heel samples from babies. They are designed to achieve a greater blood volume than puncture blade devices, as they operate by cutting through more capillaries3. Motion blade devices are also designed to minimise patient discomfort, by penetrating deep enough to obtain a sample, but to an insufficient depth to disturb deeper dermal pain fibres3.

Bringing together world-class research, design expertise and engineering excellence to create products that improve lives and reduce healthcare costs. Owen Mumford is a global industry leader in medical device design and manufacturing. We develop pioneering medical products under our Owen Mumford brands as well as custom device solutions for the world’s leading pharmaceutical and diagnostic companies.

Practical Considerations for Capillary Blood Sampling 1. Selecting the length of safety lancet The World Health Organisation (WHO) reports that pain increases with lancet penetration depth4,5, which is partly determined by the length of the lancet being used. It notes that, for a finger sample, the depth of penetration should not go beyond 2.4mm and that pressure applied during sampling compresses the skin so that ultimate puncture depth will be slightly greater than the length of lancet used. The WHO therefore recommends that 2.2mm is the maximum

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

In many countries, safety lancets have now become the routine device used by healthcare professionals to obtain a capillary blood sample

FIGURE 1. PUNCTURE BLADE DEVICE

FIGURE 2. MOTION BLADE DEVICE

length of lancet that should typically be used for finger sampling in adults and older children4. For paediatric sampling, the WHO recommends that, for children between six months and eight years, a puncture depth no deeper than 1.5mm should be used. For heel sampling in babies, it is generally recommended that the safety lancet should not penetrate deeper than 2mm, as at greater penetration depths there is a risk of making contact with bone6.

therefore, would be suitable for collecting smaller volumes of blood. With regard to lancet length, in general, the deeper the penetration depth (or, the longer the lancet) the greater the volume of blood collected. Therefore, higher blood volumes are most effectively collected by longer lancets and thicker (lower gauge) needles8.

2. Selecting for volume of blood required The volume of blood required to perform a diagnostic test varies depending on the POC device being used and the specific test being conducted. Blood glucose monitors require very small amounts of blood. For example, the Roche Accu-Chek® Performa blood glucose monitor requires a sample of 0.6 µL of capillary blood1. In contrast, there are a number of cardiac marker POC meters that require a sample of up to 250 µLof blood2 (approximately 6 drops). For newborn screening tests, a sample of up to 400 µL may be required3. There are a number of factors which influence the possible blood volume derived from any given sampling episode. These include patient hand temperature, lancet specification and post-lancing massage technique. Research has highlighted the wide variation of blood volume achieved from site to site in the same patient and with the use of different post-lancing techniques, such as pressure application7. When conducting a POC test, it is recommended that the safety lancet needle gauge (thickness) and length be chosen to collect the minimum volume of blood required to successfully complete the diagnostic test. Lancets are available in a range of gauges, as well as lengths, with gauge size being inversely proportional to needle diameter (i.e. the higher the gauge, the smaller the lancet needle diameter). For example, a 30-gauge (30G) needle has a smaller diameter than a 21G needle and,

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3. Minimising pain for the patient Research into the pain associated with the use of safety lancets highlights that the key factors implicated are ease of skin penetration and the size of the resultant injury5. The first of these factors is determined by lancet geometry and the quality of the lancet tip. The second factor is determined by lancet diameter and penetration depth. In order to make the procedure as comfortable as possible for the patient, a good quality lancet should always be selected, with a lancet size that provides just enough blood for the procedure. 4. Selecting a suitable sample site The WHO4 recommends that the ‘side of the ball of the finger, perpendicular to the lines of the fingerprint’ (4 p41), be used for capillary blood testing on adults and children over six months (weighing more than 10kg). Testing should be conducted on the middle and ring fingers; the thumb and index fingers are precluded because of the potential for calluses, and ‘the little finger because the tissue is thin’ (4 p41) (Figure 3). For pre-term and newborn babies, the side of the bottom of the heel is recommended and for those requiring repeated blood samples, the base of the heel is recommended (Figure 4)6.

How to Obtain a Capillary Blood Sample Sampling in adults The WHO recommends that the sample site should first be cleaned with alcohol and allowed


CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

to dry4. If a large blood volume is required, the sample site can be warmed. Ideally, the site should then be lanced in one quick motion, and the first drop of blood wiped away to avoid contaminating the sample with tissue fluid or debris. Gentle pressure should then be applied to encourage the flow of blood, while avoiding pressing too vigorously, as this will dilute the sample with plasma and ‘increase the probability of haemolysis’(4 p43). The sample should be collected in a blood capillary tube or similar receptacle. When the collection is complete, firm pressure should be applied to the site to stop the bleeding. The safety lancet should now be disposed of in a sharps container, and any other contaminated material disposed of in appropriate medical waste. Sampling in children Taking blood from children could be distressing, no matter how small the sample required. It is best to ask the parent to sit with the child on their lap before taking a sample. The procedure itself is technically similar to that used for adults, so guidelines for lancing and blood collection should be followed as above. To ensure there is sufficient blood flow following lancing, the parent can be asked to ‘rhythmically tighten and release the child’s wrist’(4 p44). It is important to keep the child warm by ‘removing as few clothes as possible’ (4 p44), leaving only the hand exposed. The child should, naturally, be comforted and reassured following the procedure4.

Sampling in babies Before taking a sample from babies, the heel should be washed thoroughly according to institutional guidelines9. Some guidelines recommend that the sample should be obtained using an ‘age-appropriate automated lancing device’ (6 p15). The foot should not be squeezed ‘in an attempt to increase blood flow’ (6 p17), however gentle massaging can be used if the blood flow ceases. When sample collection is complete, excess blood should be wiped from the heel and gentle pressure applied to the wound with cotton wool or gauze6.

Owen Mumford’s Unistik® Range of Safety Lancets Unistik®3, Unistik® Touch and Unistik® Tiny TouchTM are premium quality, single-use safety lancets designed to provide comfort and ease of use during capillary blood sampling. Unistik 3 is activated by pressing a button on the side of the device, while the Unistik Touch devices are activated by pressing against the sample site. Available in a range of gauge sizes and needle lengths, Unistik 3 and Touch lancets feature patented Comfort Zone Technology®, comprising eight raised pressure points at the patient end of the device. When pressed against the sample site, these pressure points stimulate nerve endings. This sends a signal of comfort to the brain, helping to reduce the pain associated with the sampling procedure10.

The world’s first pen needle system that features an integrated needle removal chamber, which offers convenient needle change.1

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Available in 4mm, 5mm, 6mm, 8mm and 12mm Compatibile3 with leading diabetes medication injection pens 1. HRW (2014). Impact of Unifine® Pentips® Plus on pen needle changing behaviour amongst people with diabetes medicating with injectable formats. 2. Melab GmbH Testing (2014). 3. Compatible with all major brands of injection pens – Compatibility data 01/09/14. * The used pen needle is secured in the interim container and must be placed in a sharps bin at the earliest opportunity.

FIGURE 3. RECOMMENDED SAMPLE SITE FOR

FIGURE 4. RECOMMENDED SAMPLE SITE FOR HEEL

FINGER SAMPLING

SAMPLING: A = FOR PRE-TERM AND NEWBORN BABIES; B = FOR BABIES REQUIRING REPEATED HEEL SAMPLING6

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

When conducting a POC test, it is recommended that the safety lancet needle gauge (thickness) and length be chosen to collect the minimum volume of blood required to successfully complete the diagnostic test

About Owen Mumford Owen Mumford manufactures class-leading medical devices that are used around the world, exporting over 85% of its products to more than 60 companies. Established over sixty years ago, it remains privately-owned and, with a history of world firsts in device innovation, offers proven design, research, development and delivery capabilities to a global audience. Selected as one of the World Economic Forum’s Global Growth Companies (2014), Owen Mumford is a trusted partner of many of the world’s best-known medical device and pharmaceutical companies, and works with international organisations to support its product users at the local level with consistent and dedicated care.

Contact Owen Mumford Ltd Brook Hill Woodstock Oxford OX20 1TU United Kingdom T: 0800 731 6959 E: info@owenmumford.co.uk owenmumford.com

References: Point of Care Diagnostic Testing World Markets. Trends, Industry Participants, Product Overviews and Market Drivers. TriMark Publications; 2015.

1

Point-of-Care (POC) Testing for a Panel of Cardiac Markers. Oxford: Diagnostic Evidence Co-operative Oxford; 2014. Horizon Scan Report 0033.

2

Shah V et al. Evaluation of a New Lancet Device on Pain Response and Success of Procedure in Term Neonates. Arch Pediatr Med 2003; 157: 1075-1078.

3

WHO guidelines on drawing blood: best practices in phlebotomy. World Health Organisation; 2010.

4

Fruhstorfer H, Schmelzeisen-Redeker G, Weiss T. Capillary blood sampling: relation between lancet diameter, lancing pain and blood volume. Eur J Pain 1999; 3(3): 283-286.

5

Guidelines for Newborn Blood Spot Sampling. London: Public Health England; 2016. First edition.

6

Grady M, Pineau M, Pynes MK, Katz B, Ginsberg B. A Clinical Evaluation of Routine Blood Sampling Practices in patients with Diabetes: Impact on Fingerstick Blood volume and pain. J Diabetes Sci Technol 2014; 8 (4): 691-698.

7

Fruhstorfer H, Muller T, Scheer E. Capillary blood sampling: how much pain is necessary? Part 2: Relationship between penetration depth and puncture pain. Prac Diab Int 1995; 12:184-185.

8

Blood Collection on Filter Paper for Newborn Screening Programs. Clinical and Laboratory Standards Institute. Wayne PA; 2007. Fifth edition, approved standard, CLSI document LA4-A5.

9

Melzack R, Wall PD. The Challenge of Pain. Harmondsworth UK. Penguin; 1982: 233 p.

10

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

Blood Tests from Needle to Pin-Prick with Caution A range of safety lancets, designed for safe, comfortable and controlled blood sampling.

Joanna Hastings, Medical Correspondent

F

OR OVER a thousand years the views of Galen (c.130 AD - c.210 AD)1,2,3 predominated medical science. He wrongly believed that humans were made up of 4 humours (blood, phlegm, black bile and yellow bile4) and that these circulated in the body like a sixties neon lamp and in various conditions one was predominant so that one might be choleric or bilious etc. This probably contributed to the long-lasting fetishism around bloodletting5 as a solution for many medical conditions. It was not just the release of blood, but the release of the ‘wrong’ humours. William Harvey6 was a dedicated medical scientist and scholar who happily dissected many a corpse and in the Western world it is to him that we owe the discovery of the circulation of blood. He realised that we have arteries to take blood from the heart and veins and to return blood to it. He appreciated that the heart acted as a pump and that the lungs acted to re-oxygenate the blood. We test blood routinely, but we leave tissue to histopathologists. What magical things can we find in blood and what do they tell us? We are all aware that a blood test can tell us the basics of blood group, full blood count, kidney function, liver function, cholesterol, glucose and hormone levels. Since red cells have an average life of 3 months, the specific study of them or their cell membrane can tell us an average of something such as the HBA1c, which tells us how much sugar the blood of a diabetic has been exposed to in the preceding 3 months. The traditional tools to analyse blood have been either the microscope or the spectrometer7. The microscope with the correct staining can tell us red and white cell numbers, shapes and sizes. It can tell us if the cells have been invaded by microorganisms such as the parasite of malaria. The spectrometer can tell us more specific chemical details of what is in the blood. The traditional spectrometer has similarities to the large early computers. It was very large but is getting smaller by the day following its own version of Moore’s law.

A laboratory-based spectrometer is a few feet wide and high depending on what is being tested, but the dream of near patient testing with smaller spectrometers is ever closer. Specific tests can now be done on just a drop of blood or micro fluid and for this to work a cutting device is required that causes minimal discomfort and provides the quantity required. Those doctors over a certain age will remember having to find a patient’s vein and then using a needle with attached syringe to extract blood. The problems were that some patients’ veins were hard to find and that the vein collapsed with the suction of the syringe, and after a while it became difficult to fill more blood bottles. This problem was largely solved by the introduction of vacuum bottles.

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The Value of Near Patient Testing (Point Of Care) Imagine that you are old and infirm and that you see the doctor in his or her surgery. At one point, he/she would take your blood or send you to his/her practice nurse to have the blood taken. However, now, more often than not, you are given a form to take to a hospital for this and any imaging that may be required. That requires a second or third journey to have the necessary investigations carried out. But imagine if the General Practitioner had the relevant test kit in his/ her surgery and just needed to prick your finger to get the result?

A Cautionary Tale of Devices and Dreams In May 2016, the estimated fortune of a lady called Elizabeth Holmes was reduced from $4.5 billion dollars to zero by the highly respected Forbes magazine. Her previous valuation was based on a revolutionary new point of care testing system called Edison as part of her company Theranos8. She had a long list of medical, defence and political experts on her board and had charmed much of Wall Street. Her company was what is known in Silicon Valley as a unicorn – the rare breed of billion dollar valued ‘tech’

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

A bad pinprick can lead to pain at the time and on-going pain, discomfort or throbbing, sometimes for weeks

companies. Sadly, slim white graceful unicorns do not exist but rhinoceroses do and they are fat and to some very ugly. The ugly truth to Theranos seems to be that it was claimed that it could do much more than was actually the case. The FDA has only approved their device for herpes virus testing and none of the other 240 tests it offers currently. Theranos is a cautionary tale for the public, investors and the medical profession. Amazing things are possible but miracles are not. Since the days of Star Trek the dream of easy to use medical technology has stayed with us. The X prize9 was set up to discover a scientific tricorder and one of the competitors was Scanadu10. However, the early days of new diagnostic medical technology are like the early days of mobile phones when the early adopters rushed to acquire the expensive ‘greatest gift to mankind’ only to find it had operational deficiencies and that, by the time it landed on their doorstep, it had already been superseded.

What Theranos Offered The company was based on the Holy Grail of a small amount of fluid to do lots of important tests quickly on a device that it had developed itself. The device was called ‘Edison’ but has

never been peer reviewed in scientific journals and once the FDA started investigating it had grave concerns and sanctioned only 1 test out of 24011 the company had previously claimed for its Edison device (it is now thought that these other tests are performed on conventional existing laboratory technology). This one test was for the herpes virus12. Thomas Edison was the undoubted genius of the American technical revolution alongside Nikola Tesla13. Tesla’s name has been used by entrepreneur and visionary Elon Musk14 who has created a successful electric car/electric battery company but, sadly, Edison’s light has not shone on Theranos15,16.

Summary A bad pinprick can lead to pain at the time and on-going pain, discomfort or throbbing, sometimes for weeks. In some cases, a feeling of paraesthesia may occur. More rarely infection may be caused. Pinprick testing not done by you requires the correctly manufactured, safe stylette devices administered by trained people who do not use excessive force. The tests carried out should be scientifically validated and reliable. Trust is a key component of testing. Better pricing is good, but quality of results is most important.

References: http://www.bbc.co.uk/history/historic_figures/galen.shtml Accessed 4/6/2016 http://www.sciencemuseum.org.uk/broughttolife/people/galen Accessed 4/6/2016 3 http://www.sciencemuseum.org.uk/broughttolife/techniques/humours Accessed 4/6/2016 4 http://www.sciencemuseum.org.uk/broughttolife/techniques/humours Accessed 4/6/2016 5 http://www.sciencemuseum.org.uk/broughttolife/techniques/bloodletting Accessed 4/6/2016 6 http://www.sciencemuseum.org.uk/broughttolife/people/williamharvey Accessed 4/6/2016 7 http://bwtek.com/spectrometer-introduction/ Accessed 4/6/2016 8 https://www.theranos.com/ Accessed 6/6/2016 9 http://www.xprize.org/grand-challenges/life-sciences Accessed 8/6/2016 10 https://www.indiegogo.com/projects/scanadu-scout#/ Accessed 8/6/2016 11 https://www.theranos.com/test-menu Accessed 6/6/2016 12 http://www.accessdata.fda.gov/cdrh_docs/reviews/k143236.pdf Accessed 6/6/2016 13 http://www.history.com/topics/inventions/nikola-tesla Accessed 6/6/2016 14 http://www.biography.com/people/elon-musk-20837159 Accessed 6/6/2016 15 http://www.bloomberg.com/news/articles/2016-06-03/theranos-says-only-1-of-results-affected-some-doubt-tests Accessed 6/6/2016 16 http://www.theverge.com/2016/3/28/11320328/theranos-comparison-study-labcorp-quest-diagnostics-not-reliable Accessed 6/6/2016 1 2

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

The Point to Point of Care Testing Contact activated single use lancets, designed to make capillary sampling simple and easy.

Dr Charles Easmon, Editor

Comfort Zone Technology ®

30G

1.5mm The Economic Perspective Point of care tests require a capital outlay for the equipment, the reagents, the calibration and the maintenance of the equipment. To ensure that the tests are accurate and have an acceptable level of sensitivity and specificity, ideally, tests should be aligned with a traditional laboratory that can undertake regular quality checks and control1. The equipment should be bought from trusted manufacturers who have obtained the appropriate CE2 markings and where necessarily approval from the Medical & Healthcare Products Regulatory Agency (MHRA3) and the National Health Service (NHS) supply chain4. Once bought, the equipment must, of course, be maintained and checked by calibration with ‘control’ reagents. The reagent strips used must be kept and maintained in the right conditions and not used beyond their expiry date. An assigned practice staff member must be in charge of all these quality control aspects and a clear policy should be adopted and adhered to by all5. Once all this is taken into account, the cost per test may often be the same or even slightly higher than those at a hospital or local laboratory. A practical cost element in England may be the fact that tests done outside the practice do not impact on the GP budget whereas point of care tests do.

The Professional Perspective

28G

Tests are key tools that keep us and our patients on the right track. Without them we can veer off into the wrong diagnosis and unknown directions. A half-baked cake is a waste of ingredients and is inedible. Much has been wasted. A diagnosis without diagnostic tests is often like a half-baked cake. A GP can clinically suspect anaemia or a hormone disorder but, without confirmatory tests, the diagnosis may be just speculation. Managing homeostasis in a diabetic requires knowledge of what is the actual blood or urine sugar level or the HBA1C. Although we, as medical professionals, know that tests are important, we make this key part of our diagnostic armoury difficult by requiring secondary or tertiary appointments in other locations to get this done. The working patient has to schedule and plan more time off work. The non-working patient may need to enlist relatives, friends or charities to get to the ‘testing’ appointment, all of which has economic and social costs not reflected in the NHS budget. If point of care testing was cost-efficient, effective and easy to use and maintain it would be the ideal choice for many simple tests in General Practice. The experience of medical staff in restricted environments can give some clues

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

A GP can clinically suspect anaemia or a hormone disorder but, without confirmatory tests, the diagnosis may be just speculation

as to the utility and frustrations of point of care testing. On board cruise ships, two doctors and a nursing team may be responsible for several thousand patients. The only ground based laboratories are on shore and so, while at sea, the cruise medical staff often must rely on point of care tests6. A positive point of care test at sea has been the biochemistry test but negatives have occurred with regularly failing equipment for testing haemoglobin (as reported to the author).

The Patient Perspective “The doctor will see you now” are wonderful words that many a patient looks forward to hearing, having finally booked their appointment and got their slot. Their face falls when told they must next plan and proceed to the local hospital or assigned laboratory for tests. Many fail to comply for reasons other than the lack of intent7.

Some who fail to have their tests subsequently miss follow up appointments with their GP caused by embarrassment at not having had the tests carried out or seeing such follow up as pointless without the results. One group that we happily and successfully screen using point of care tests is newborns8.

Summary A General Practice or Clinical Commissioning Group (CCG) that introduces point of care testing will probably not save thousands or millions for themselves but they will save money for the overall economy and make life easier for many of their patients newborn, working, disabled and retired. The patient who does not have to take extra time off work to attend hospital for a blood test has a clear benefit, as does the elderly or disabled patient who does not have to send valuable time and effort in doing the same.

References: http://www.cmft.nhs.uk/info-for-health-professionals/laboratory-medicine/point-of-care-testing

1

http://www.ce-marking.org/what-is-ce-marking.html Accessed 8/6/2016

3

https://www.gov.uk/topic/medicines-medical-devices-blood/medical-devices-regulation-safety

4

5

Accessed 8/6/2016 https://www.supplychain.nhs.uk/product-news/contract-launch-briefs/2013/september/point-of-care-testing-systems/ Accessed 8/6/2016 http://www.cmft.nhs.uk/info-for-health-professionals/laboratory-medicine/point-of-care-testing/poct-policy Accessed 8/6/2016

6

http://onlinelibrary.wiley.com/doi/10.1111/jtm.12086/full Accessed 8/6/2016

7

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/228836/7432.pdf

8

10 | WWW.PRIMARYCAREREPORTS.CO.UK

Accessed 8/6/2016

2

Accessed 8/6/2016 http://www.ncbi.nlm.nih.gov/pubmed/27265561 Accessed 8/6/2016


CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

Antigen and Antibody Tests That Can Save Lives and Resources Joanna Hastings, Medical Correspondent

T

HE CLEVER part of medical biochemistry is to get something that you can identify to attach to something that you otherwise could not. Antigens are parts of things whether that is part of a virus, bacteria, parasite or chemical. Antibodies are what the immune system has developed to identify these parts. Once science was able to produce clones of antibodies specific to certain antigens, a whole new world of scientific investigation and detection opened up and this is the province of many point of care tests. As an example, the pregnancy test is based on monoclonal antibodies to the pregnancy hormone HCG1. These monoclonal antibodies will next year, 2017, see the 30th anniversary since they were first pioneered by the remarkable work of Georges Kohler and Cesar Milstein2. Few of us would say that cancer has any good qualities but without cancer cells’ continuous reproductive capacity we would not have monoclonal antibodies. The story gets more complex as we now use humanized3 monoclonal antibodies to attack cancers as therapy and this has revolutionised the treatment of once universally fatal melanomas4.

Pinprick Tests that can Save Lives and Resources (Rapid Diagnostic Detection Tests) RDTs are lateral flow immuno-chromatographic antigen-detection tests, which rely on the capture of dye-labeled antibodies to produce a visible band on a strip of nitrocellulose, often encased in plastic housing, referred to as cassettes. With malaria RDTs, the dye-labeled antibody first binds to a parasite antigen, and the resultant complex is captured on the strip by a band of bound antibody, forming a visible line (T - test line) in the results window. A control line (C- control line) gives information on the integrity of the antibody-dye conjugate, but does not confirm the ability to detect parasite antigen5.

In the exotic diseases, malaria (a parasite), Filaria (a parasite), Human Immunodeficiency Virus (HIV), hepatitis B & C 6 (viruses), staphylococcus (bacteria) can all be detected by monoclonal antibodies. The parasite of malaria has 4 human types (Falciparum the most deadly, malaria, ovale and vivax) and to ensure a potentially fatal diagnosis is not missed the rapid diagnostic detection tests7 focus on falciparum but may also detect the other types. There are now more than 200 Malaria rapid diagnostic tests on the market8. With the rise of travel to exotic destinations this diagnosis is becoming more important to the UK General Practitioner and a travel history should always be enquired about. Malaria symptoms can be the great mimicker of many other diseases and can easily be mistaken for other causes of fever9, influenza, migraine or other headaches or food poisoning. If a timely diagnosis is not made, death of course may occur but each year there are many cases of lives saved only after very expensive and extensive periods on Intensive Care Units. For viruses, the antigen may be any part of the virus itself (the DNA or RNA or the protein capsule). In the UK, the number of undiagnosed HIV is estimated at many thousands10. Each of these blood borne viruses could easily and efficiently be detected by separate pin-prick blood tests and results made available after prior counselling within minutes. The health benefits of an early diagnosis to the individual, society and to the National Health Service are almost incalculable but can be estimated in billions of pounds.

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Care with Antibiotics Medical professionals worldwide are exhorted to reduce the prescription of antibiotics. The resistance genes for antibiotics are spreading far and wide since, as a member of the House of Lords Select Committee 11 on antibiotic resistance once said anonymously, the evolution of bacteria is ‘Darwin at the speed of light’.

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

The health benefits of an early diagnosis to the individual, society and to the National Health Service are almost incalculable but can be estimated in billions of pounds

However, many a doctor is faced by an insistent patient with a sore throat who claims that if it is not treated with antibiotics, what started as an upper respiratory tract infection (URTI) will become a lower respiratory tract infection (LRTI) and what then? If, as is widely used in the United States of America, the doctor has an ‘instant’ throat swab test for Streptococcus, then the patient can be reassured one way or the other if the bacteria identified is only a harmless commensal. Blood or micro fluid versions of such tests may be useful additions in the future and, with advances in genetic testing, may actually tell us what antibiotics the infection is already resistant to or which it will respond to.

Summary Testing advances with antigens and antibodies are developing at a healthy rate and, with good scientific validation and protocols, will be of further clinical benefits to General Practitioners as time progresses. However, clinicians need to be vigilant that their chosen test does what it says it does consistently and reliably and is regularly calibrated to ensure that this is actually the case. Those who perform the test need to be able to ensure the safety of the patient, with low risk to themselves from needle-stick injuries, ensure safe disposal of any sharps and ensure that the optimal device for obtaining ‘testable’ blood or micro fluid is used.

References: http://www.abpischools.org.uk/page/modules/infectiousdiseases_immunity/immunity5.cfm

1

12 | WWW.PRIMARYCAREREPORTS.CO.UK

Accessed 6/6/2016

2

http://www.bio.davidson.edu/molecular/MolStudents/01rakarnik/mab.html Accessed 6/6/2016

3

http://pdl.com/technology-products/what-are-humanized-monoclonal-antibodies/ Accessed 6/6/2016

4

http://melanomainternational.org/melanoma-facts/melanoma-treatment-stage-iv/#.V1ZakCMrKlM

Accessed 7/6/2016

5

http://www.who.int/malaria/areas/diagnosis/rapid-diagnostic-tests/about-rdt/en/ Accessed 7/6/2016

6

https://www.nice.org.uk/advice/mib24 Accessed 8/6/2016

7

http://www.who.int/malaria/areas/diagnosis/rapid-diagnostic-tests/en/ Accessed 7/6/2016

8

http://www.who.int/malaria/areas/diagnosis/rapid_diagnostic_tests/en/ Accessed 7/6/2016

9

http://tiny.cc/iyy6by Accessed 7/6/2016

10

http://www.hivaware.org.uk/facts-myths/hiv-statistics Accessed 8/6/2016

11

http://www.publications.parliament.uk/pa/cm201415/cmselect/cmsctech/509/509.pdf Accessed 8/6/2016


CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

Reliable Micro Fluid Results Dr Charles Easmon, Editor

Re-useable insulin delivery pens designed to simplify injections. • Sensitivity and specificity are terms used to evaluate a clinical test. They are independent of the population of interest subjected to the test. • Positive and negative predictive values are useful when considering the value of a test to a clinician. They are dependent on the prevalence of the disease in the population of interest. • The sensitivity and specificity of a quantitative test are dependent on the cut-off value above or below which the test is positive. In general, the higher the sensitivity, the lower the specificity, and vice versa1. The world of testing relies on statistical probability, calculus and calculation. Results need to be interpreted both in terns of the individual and the community in which the testing is done. At medical school, many of us struggled to understand sensitivity, specificity, valid ranges, standard deviations, positive and negative predictive value. Blood is what the heart pumps around and it is returned deoxygenated in the veins. If spun in a centrifuge, blood has the clear component we call serum and the more solid component of the red and white cells. When a pinprick test is carried out, the fluid that oozes out is a mixture of blood as in a normal venepuncture, serum as in a centrifuged process and intracellular fluids. Blood and micro fluid tests can attempt to define a specific thing as negative or positive or give a range of values, some of which are normal and some of which are deemed abnormal. In the positive or negative context, the ideal test would always tell you when the person who has the thing actually has it (100% sensitive) or always when the person who does not have it, if this is the case (100% specific). No test is 100% sensitive or specific. Assuming that we were not colour blind, if everyone with a specific disease like diabetes turned green and everyone with a heart attack turned bright blue, diagnosis would be much easier and the use of proxy measures such as blood tests would be much less needed. But the fact is that we have to use proxy measures, as in clinical tests to determine

disease, diagnoses and results and these, by their nature, are never perfect.

Negative or Positive (or Interesting?) The great lateral thinker, Edward de Bono2, encourages us to think beyond just negative and positive (or plus) but to consider, also, things somewhere in between, which he calls ‘interesting’. This approach is hard to apply to clinical blood or micro fluid tests. We need to know if someone has malaria or not or Hepatitis C infection or not. The first principle is sensitivity and the second is specificity, but after that you want to know both the positive predictive value and the negative predictive value for the population in which the test is being used. Specificity is specific to those not having disease whilst sensitivity is sensitive to those who do have the disease. Sensitivity = true positive rate Specificity = true negative rate False positive rate = 1- specificity For example, if the specificity is 0.65 or 65% of all tests deemed negative are actually negative, that means that 35% of tests are false positives. The confusion often comes at the next stage when we need to realise that, although we are still dealing with similar numbers, both the context and the denominator have changed. So, whilst sensitivity and specificity are in no way dependent on the actual population to be tested, the Positive and Negative Predictive Value3 (PPV and NPV) are entirely dependent on the population to be tested and, for example, will have different values for a blood test for heart attack on a cardiac ward than on a health farm. The ‘Post test probability’ of a disease (which is highly dependent on the prevalence of the disease in the sample) is a Bayesian4 concept. In the simplest of terms, it tells us that, if the sample is not enriched with disease, the PPV decreases and the NPV increases.

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The Range of a Blood or Micro Fluid Result Laboratories must decide what range to call normal for many tests from cholesterol to Haemoglobin and they usually use the standard

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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

When a pinprick test is carried out, the fluid that oozes out is a mixture of blood as in a normal venepuncture, serum as in a centrifuged process and intracellular fluids

statistical Bell curve to do this. They take the area covered by 95% of a ‘normal’ population and exclude the 5% of outliers (2.5% at the lower end and 2.5% at the higher end). However, caution is required about the normal range in terms of any individual test, that test in the context of other related tests. An individual test range of heights can be a good way of explaining the problem to yourself or to a patient. In an average high street, we do not see many giants or many dwarves and so, if we estimate a range of height based on our observed Bell curve, a dwarf and a giant would be outliers, but they are not ‘abnormal’ in either their humanity or their physiology. Isolated gamma GT is a good example in the context of a range of tests because if the liver is damaged by viruses, fatty infiltration, alcohol, chemicals or inflammation one would and should expect abnormalities in the alanine trnsaminase (ALT), aspartate aminotransferase (AST), alkaline

phosphatase as well as the gamma GT. How the results vary between them all can give some clue as to the most likely cause of the liver damage. However, an isolated rise in gamma GT with normal ALT, AST and alkaline phosphate may be an individual quirk or caused by a harmless genetic conditions such as Gilbert’s disease5.

Summary We can put a drop of something on to something else and say it shows X, Y or Z but we must always question the accuracy and the consistency of the answer given because, to fail to do so, could lead to wrongful diagnoses in both senses (false negatives and false positives) and could lead to the mismanagement of a patient’s care (high, normal or low blood sugar or cholesterol for example). The ideal tools to take the ‘drop of something’ must be sterile, effective and cause minimal pain to the patient.

References: http://ceaccp.oxfordjournals.org/content/8/6/221.full Accessed 6/6/2016

1

2 3

4

Accessed 6/6/2016 http://whatis.techtarget.com/definition/Bayesian-logic Accessed 8/6/2016

5

14 | WWW.PRIMARYCAREREPORTS.CO.UK

http://whatis.techtarget.com/definition/PMI-plus-minus-interesting-retrospective Accessed 8/6/2016

http://sphweb.bumc.bu.edu/otlt/MPH-Modules/EP/EP713_Screening/EP713_Screening5.html

http://www.nhs.uk/conditions/Gilbertssyndrome/Pages/Introduction.aspx Accessed 8/6/2016


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CAPILLARY BLOOD SAMPLING – ACHIEVING THE PERFECT SAMPLE

Notes:

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Primary Care Reports – Capillary Blood Sampling – Achieving the Perfect Sample  

Primary Care Reports – Capillary Blood Sampling – Achieving the Perfect Sample – Owen Mumford

Primary Care Reports – Capillary Blood Sampling – Achieving the Perfect Sample  

Primary Care Reports – Capillary Blood Sampling – Achieving the Perfect Sample – Owen Mumford