Diagnosis and screening for psychotic disorders in a study of the homeless.

In a survey of homeless men, the authors found that screening scales for psychotic symptoms (Psychiatric Epidemiology Research Instrument) and signs (6-item scale of observational ratings) predicted a rating of psychosis (possible, probable, or definite) on a diagnostic interview (Structured Clinical Interview for DSM-III-R: Psychotic Disorders) reasonably well, in a sample where psychosis was common. Although the two scales performed well when used in conjunction, neither scale showed adequate predictive power when used alone. The authors conclude that screening for psychotic disorders in community studies is feasible for some purposes. They suggest approaches to the use of diagnostic interviews and screening scales in future community studies that might enhance the interpretability as results as well as the efficacy of screening.