Tests using single markers

Abstract

This chapter describes screening based on the measurement of a single variable. Before considering the screening test in detail, it is necessary to consider the disorder for which screening is being carried out, its definition, its prevalence, its natural history, and the efficacy of its treatment or prevention. Information on the overlap of test values from affected and unaffected individuals is necessary to determine detection rates and false-positive rates, which, together with data on prevalence, permit the estimation of the risk of being affected. This information is also needed for subsequent screening or diagnostic tests.