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

Abstract

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.