Informed choice for screening: implications for evaluation

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Abstract
Value all benefits and harms Evidence from randomised trials that screening reduces mortality is necessary but not sufficient to justify screening. Decisions should be based on an assessment of all the benefits and harms, not only of the screening test but also of follow up tests and treatments. As the UK criteria state, the screening programme must be clinically, socially, and ethically acceptable to the public and the benefits outweigh the harm.3 A holistic approach to evaluation requires studies to identify the benefits and harms perceived by consumers and clinicians. Harms include: Complications of investigation of screen detected abnormalities Unexpected effects, such as increased morbidity and mortality from side effects of screening or subsequent management Overdetection—the identification of disease that would not have presented during the person's lifetime, and Psychosocial effects. Some harms or downsides may seem trivial, but, unlike the benefits, occur soon after screening and are common. For example, biennial mammographic screening has been estimated to avert only two deaths in 1000 women aged 50-59 over 10 years but requires 5000 screens, 242 recalls, and 64 women to have at least one biopsy.5 Moreover, five women will have a ductal carcinoma in situ detected, some of which may never have progressed if left untreated. This information may lead some people to decide that the downsides of screening outweigh avoidance of longer term serious but rare outcomes.6 Consultation about screening policy between policy makers and an informed public is essential. The public can be involved through methods such as citizen juries, deliberative panels, and round table discussions with community members.7 Community surveys among representative samples can provide policy makers with useful information about how benefits are valued against harms in the population.6 8 9 Preferences can be measured directly: “Given the benefits and harms, would you prefer to be screened or not screened?” or through utility measurement techniques that assess individuals' preferences through specific trades or gambles (choices) associated with the benefits and harms of screening.