Prospective diagnosis of the initial prodrome for schizophrenia based on the Structured Interview for Prodromal Syndromes: preliminary evidence of interrater reliability and predictive validity.

OBJECTIVE This study was conducted to determine the interrater reliability and predictive validity of a set of diagnostic criteria for the prodrome of the first episode of schizophrenic psychosis when based on the Structured Interview for Prodromal Syndromes. METHOD The subjects were patients referred for evaluation because of a suspected schizophrenia prodromal syndrome. For the reliability study, two to four raters independently diagnosed 18 patients on the basis of face-to-face or videotaped interviews. For the validity study, 6- and 12-month outcome data were collected for 29 patients. RESULTS Agreement in differentiating prodromal from nonprodromal patients was 93%. The prodromal features had converted to schizophrenic psychosis for 46% of the prodromal patients at 6 months and for 54% at 12 months. CONCLUSIONS In small groups of subjects, these diagnostic criteria for the schizophrenic prodrome and the Structured Interview for Prodromal Syndromes showed promising interrater reliability and predictive validity.