Sensitivity determination of cancer screening programmes with the aid of "interval cases".

The determination of "interval cases" bears great significance in the estimation of the diagnostic sensitivity of a cancer screening programme and the setting of an appropriate periodicity of the screening terms. The concept can only be applied purposefully with regard to tumor kinetics and its relationships to the probability of tumor detection through the examination methods applied. The methodical considerations presented also result in a criticism of the "length-biased sampling" which has constantly been pointed out in the screening theory in recent years.