Many probabilities are uncertain, and the accumulation of a cascade of events, each with an uncertain probability, can result in substantial error. These complex events occur at various times, often over decades. To describe the clinical consequences of the alternative screening strategies more comprehensively, the panel commissioned a study to model the effects of each strategy for average-risk people to begin screening at age 50 and to continue in the same strategy until age 85 or death. The model included not only the screening test but also the diagnostic and surveillance testing induced by the screening test. All of the screening strategies were found to be more effective in saving lives than no screening.
Individual strategies vary in the number of cancers prevented, tests undertaken, and risk.
All strategies result in many false positive tests. All strategies include colonoscopy, to a greater or lesser extent, and much of the risk of all screening strategies is related to colonoscopy. Although this risk is relatively small for each procedure, it accumulates for a population, as some members undergoing screening and diagnostic and surveillance testing repeatedly. . All contents 2001 American Gastroenterological Association. All Rights Reserved.