A Review on the Methodologyfor AssessingDiagnosticTests

Evaluation of diagnostic tests by the following principles are reviewed: error rates, scores based on posterior probabili-ties, and the excess loss considered in a decision theoretic context. Error rates or the complementary non-error rates, specificity and sensitivity, are simple measures which pro-vide a rough indication of the discriminative value. In clinical practice, where a test serves as a decision support together with other information, conversion of test results to posterior probabilities is recommended. An aggregate score of these probabilities expresses the value of the test. Finally, in simple, well-defined cases-for example, screening situa-tions, where the prevalence of disease and the relative consequences of false-positive and-negative classifications can be estimated-a Bayesian decision analysis is appropri-ate. The optimal discrimination limit is selected, and the tota