[Consequences of uncertainty and overdiagnosis in screening]

Uncertainty in screening has consequences for real people's lives. This article describes the various types of uncertainty, such as false results, diagnostic probabilities, consistency in diagnosing, bias in screening research, cumulative risk of false results over a life span, and the potential risk with certain procedures. Overdiagnosis as an unrecognised cause of harm in screening is also discussed. Every offer of a screening contains a hidden message, saying: "you are not able to assess your own health; even if you think you are healthy, you may have an unknown disease". Hence, the worst effect of screening might be the undermining of people's confidence in their ability to assess their own health. If the concept of screening conveys the idea in the population that only medical examinations can say anything about health status, it implies the use of many other activities in the health care system to convince healthy people that they are still healthy.