Applicability of the Chinese version of the Prodromal Questionnaire

Early detection and intervention of psychosis is clinically important. This study aimed to test the applicability of the Chinese version of the Prodromal Questionnaire (CPQ) for identifying prodromal states of psychosis.

This is a two-group cross-sectional comparative study. The Prodromal Questionnaire (PQ) was translated into traditional Chinese based on Brislin's Revised Model. Like the PQ, the CPQ provides results on four subscales: (1) positive symptoms, (2) negative symptoms, (3) disorganized symptoms, and (4) general symptoms. An expert panel of five senior psychiatrists established the content validity of the CPQ. The experimental group was a sample of 100 first-visit patients to a psychiatric outpatient department (FVPOD). The comparison group comprised 98 nursing students without any history of psychiatric disturbances. Both the CPQ and the Chinese Health Questionnaire-12 were administered to all 198 subjects. Clinical psychosis was assessed using the Chinese version of the Diagnostic Interview for Genetic Studies, and 30 of the 100 FVPOD subjects were thus identified as psychotic patients and the remaining 70 were non-psychotic.

Content validity of the CPQ was confirmed by an expert panel of five senior psychiatrists, achieving an overall reliability in the range of 0.86-0.93. The FVPOD group and comparison group had significantly different mean scores on all four subscales of the CPQ. In identifying psychotic cases, the 35-item positive symptom subscale had high sensitivity (97%) and low specificity (30%) with a cutoff value of 8. Due to the low specificity, patients identified as potential psychotic cases were referred for further clinical evaluation.

Applicability of the CPQ was demonstrated by its high reliability and good ability to discriminate between clinical patients and a comparison group. The 35-item positive symptom subscale can be useful alone in general mental health settings for screening psychotic cases.