[Summary of a new assessment strategy in positive occult blood tests in mass screening].

Effective regulations of the Federal Association of Health Insurance Physicians (Kassenärztliche Bundesvereinigung) require prompt evaluation of positive fecal occult blood tests (FOBTs) in the nationwide cancer screening programme using rectoscopy, double contrast barium enema and colonoscopy, the latter occasionally being recommended as a primary investigation. In symptomless screenees the prevalence of positive FOBTs is much higher than that of detected malignancies. Hence a major proportion of all follow-up investigations are negative. A simple model yields the following conclusion: waiving immediate and maximum follow-up efforts in favour of a two-stage screening procedure will result in a loss of some detectable cases; on the other hand, the number (and with it inconveniences, risks, and costs) of follow-up investigations may be reduced to such an extent that a two-stage screening programme along with some modifications of the FOBT itself should be tested.