DIAGNOSTIC INTERVIEW FOR GENETIC-STUDIES - RATIONALE, UNIQUE FEATURES, AND TRAINING

This article reports on the development and reliability of the Diagnos tic Interview for Genetic Studies (DIGS), a clinical interview especia lly constructed for the assessment of major mood and psychotic disorde rs and their spectrum conditions. The DIGS, which was developed and pi loted as a collaborative effort of investigators from sites in the Nat ional Institute of Mental Health (NIMH) Genetics Initiative, has the f ollowing additional features: (1) polydiagnostic capacity; (2) a detai led assessment of the course of the illness, chronology of psychotic a nd mood syndromes, and comorbidity; (3) additional phenomenologic asse ssments of symptoms; and (4) algorithmic scoring capability. The DIGS is designed to be employed by interviewers who exercise significant cl inical judgment and who summarize information-in narrative form as wel l as in ratings. A two-phase test-retest (within-site, between-site) r eliability study was carried out for DSM-III-R criteria-based major de pression, bipolar disorder, schizophrenia, and schizoaffective disorde r. Reliabilities using algorithms were excellent (0.73 to 0.95), excep t for schizoaffective disorder, for which disagreement on estimates of duration of mood syndromes relative to psychosis reduced reliability. A final best-estimate process using medical records and information f rom relatives as well as algorithmic diagnoses is expected to be more reliable in making these distinctions. The DIGS should be useful as pa rt of archival data gathering for genetic studies of major affective d isorders, schizophrenia, and related conditions.