Reliability and concordance in the subtyping of schizophrenia

The authors examined the reliability, frequency, concordance, and demographic characteristics of subtypes of schizophrenia in patients from the Iowa 500 study as defined by four major diagnostic systems: DSM-III, Research Diagnostic Criteria (RDC), ICD-9, and the Tsuang-Winokur criteria. Reliability was higher in diagnostic systems with operationalized than in those with unoperationalized criteria and consistently higher for the paranoid subtype. The frequency of individual subtypes varied widely for the different systems. Concordance for subtype diagnoses between systems ranged from quite high to quite low. Demographic characteristics of the individual subtypes were similar according to all systems.