Screening-related prevalence and incidence for non-recurrent diseases

Expressions for prevalence (P) and incidence (I) in open dynamic populations are derived. When screenings are performed every s:th year, P and I will be functions of s. It is shown how the true values of P and l, which would have been obtained with continuous screening, can be estimated from screening data. A solution is also given to the following problem: Given that subsets of the population have different P's and I's and that resources are limited so only a fraction of the total population can be screened every year, which should be screened and how often in order to maximize the total proportion of detected cases