Neuropsychiatric decision making: the role of disorder prevalence in diagnostic testing

Although the performance of medical diagnostic tests is usually described in terms of their sensitivity and specificity, these accuracy indices by themselves are of little help to clinicians who need to make decisions about patient care. Estimating the probability that a patient with a positive or negative test has or lacks a disorder requires the clinician to include the pretest probability of the disorder in the interpretation of the test result. This article described several approaches to the problem of interpreting diagnostic data in actual clinical contexts.