Informed consent for screening by community sampling.

Screening requires that people with no symptoms undergo testing to find out whether they have occult disease. Therefore, there is a strong ethical imperative to ensure that high-quality evidence is available from randomized trials and that screening is judged to have more benefits than harms. But how should this judgment be made, and by whom? Delaying a death by screening is a substantial benefit that accrues to few people, but screening also has disadvantages and presents harms to many people. Benefits are often long term and include reductions in mortality or in morbidity due to the disease.1 Disadvantages or harms are often immediate, arising from the screening test itself or the need for further investigation in those whose test results are positive. There may be inconvenience and discomfort for those screened. In up to 5% to 10% of screenees,1, 2 false-positive test results may result in anxiety and physical harm associated with further investigation. Some true-positive patients have abnormalities that would not have led to any adverse events during their lifetime and therefore have no potential for any benefit from screening.3–5 As an example, consider mammographic screening in women starting at 40 years of age. To avert 1 death in the next 10 years, more than 1000 women need to be screened 5 times, and about 300 would be recalled for further investigation.6 Most of these would turn out to have false-positive results. In some countries, about 35 women would have biopsies, whereas in others, the number could be three times as great.7 About 15 cases of invasive cancer would be detected early, and about 3 ductal carcinomas in situ would be found, some of which might never have progressed.6 Given this information, individuals may vary in their desire to be screened. Screening for communicable disease is different. In addition to the benefits and harms for the individual, society benefits because of reduced transmission. Similarly, for some noncommunicable diseases, such as phenylketonuria, screening may save money for society and extend the benefits beyond the individual. However, most current screening is for noncommunicable disease and costs society more than it saves. Any benefit of screening accrues to—and harms or inconveniences are borne by— the individuals being screened and their families, and the total benefit to society is the sum of the net benefit to these people. In this circumstance, it seems inappropriate to frame the objective of screening as a reduction in mortality and disability from the disease being detected, when the goal of achieving this “hard” end point may be won at the cost of decreased health—broadly defined—for people being screened.8–11 It seems more appropriate that people to whom screening is being offered should give informed consent to be screened.