176 | Noncommunicable Diseases in Saudi Arabia
substantial net benefit, whereas a grade of B indicates that there is either (1) a high certainty of moderate net benefit or (2) a moderate certainty of moderate to substantial net benefit. Given the current state of evidence, there is weak justification for mammography in average-risk, asymptomatic women. A large, well-designed 25-yearlong RCT finds no effect of mammography on mortality (Miller et al. 2014), with virtually the same findings for women ages 40–49 and 50–59. Moreover, there is little or no evidence that mammography has a beneficial effect on breast cancer mortality rates (Gøtzsche and Jørgensen 2013). For this reason, a panel of experts appointed by the Swiss government has recommended stopping mammography in Switzerland (Biller-Andorno and Jüni 2014). A review of systematic reviews finds no consistent conclusion regarding the effectiveness of mammography (Raichand et al. 2017). It is possible that a newer type of mammogram called digital breast tomosynthesis (also known as three-dimensional mammography) is superior to the standard version, but the available evidence is insufficient to draw any conclusions. Co-testing with both mammography and magnetic resonance imaging (MRI) has high sensitivity (Warner et al. 2008). As a result, co-testing has been incorporated into the breast cancer screening guidelines for women who are at high risk, such as those with a known BRCA1 or BRCA2 gene mutation (see, for example, Saslow et al. 2009; UK National Institute for Clinical Excellence 2019a; Warner et al. 2018). Screening for and treatment of childhood obesity can reduce BMI slightly in the short run, but it is unclear whether this small reduction is clinically significant and whether it would be sustained and have longer-term benefits. The US Preventive Services Task Force (2017) states that comprehensive, intensive behavioral interventions in children and adolescents who are obese can reduce weight for up to 12 months. According to a review by Kumar and Kelly (2017, 251), “Lifestyle interventions have shown only modest effect on weight loss, particularly in children with severe obesity,” and there is limited information on the longterm efficacy and safety of weight loss medications and bariatric surgery in children. Similarly, a review of diet, physical activity, and behavioral interventions for the treatment of overweight or obese children concludes that such interventions “may be beneficial in achieving small, short-term reductions in BMI,” but the small reduction “may not be sufficient to improve or prevent obesity-related comorbidities” and the quality of the evidence overall is “low or very low.” The researchers cite the need for longer-term follow-up (Mead et al. 2017). Using only screen-and-treat policies for high blood sugar is unlikely to have a substantial impact on type 2 diabetes. In a systematic review of 49 studies of screening tests, researchers find that screening for high blood sugar using HbA1c is likely neither specific nor sensitive for detecting prediabetes, whereas fasting glucose is specific but not sensitive (Barry et al. 2017). Despite the inaccuracy of screenings, interventions in people identified through screening as having prediabetes have shown some efficacy in preventing or delaying type 2 diabetes.
COST-EFFECTIVENESS OF SCREENING In Western countries, population-wide colorectal cancer screening is regarded as cost-effective in adults ages 50 and older. A review conducted for the US Preventive Services Task Force concludes that the cost-effectiveness of
