Issues of validity in the diagnostic interview schedule

The Diagnostic Interview Schedule, the chief instrument in contemporary studies in psychiatric epidemiology, enhances the reliability of psychiatric diagnosis and enables lay interviewers to closely reproduce psychiatric interviews. However, despite frequent references in the literature to the validity of the Diagnostic Interview Schedule, most studies fundamentally represent variations of reliability paradigms to the neglect of criterion-related validity. Mistaken assertions of validity persist in the psychometric language used to describe the Diagnostic Interview Schedule. This article examines the basis for claims and counterclaims of validity in accordance with standard psychometric definition, and identifies sources of erroneous reasoning in attempts to infer validity from reliability. The article presents a general framework organizing the process of diagnostic validation and discusses strategies for research seeking to validate psychiatric diagnoses achieved through the Diagnostic Interview Schedule.