The predictive value of a diagnostic test is highlydependent upon disease prevalence. Disease preva-lence, however, varies widely from patient to patient.Since patients in whom the diagnosis is unclear arethe ones most likely to get a diagnostic test, it is help-ful to standardize the predictive value of a diagnostictest to a disease prevalence of 50%. Even more usefulwould be to present predictive values standardized todisease prevalences of 25%, 50%, and 75%