The ethics, the risks and the benefits of screening.

The ethical principles underlying screening are reviewed. It is concluded that the ethical requirements for the introduction of screening are stringent, and that screening should not be offered in the absence of unequivocal evidence of effectiveness except in a carefully conducted research study. Part of the reasons for this are the risks associated with screening, which extend beyond the risk of the test itself, to those associated with invitations for screening, false reassurance for false negatives, the diagnostic process and the problem of false positives, and the overtreatment of those with borderline abnormalities. Finally, the benefits expected from screening are considered, especially reduction in mortality from the disease, but also reduction in incidence if a precursor is detected by the test, less radical treatment for cases detected, reassurance for those who test true negative, and resource savings, though it has to be demonstrated that these exceed resource costs.