Cross Validation of the Prodromal Questionnaire 16-Item Version in an Adolescent Help-Seeking Population

Abstract

Abstract The Prodromal Questionnaire 16-item version (PQ-16) is used as a screener in the early detection of psychosis. We wished to cross-validate it in a help-seeking population of adolescents aged 12–17 who had been referred for assessment and treatment to an outpatient Center for Child and Adolescence Psychiatry (CCAP). To examine the psychometric properties of the PQ-16 for adolescents, we used reliability analysis and receiver-operating-characteristic (ROC) curves. The internal consistency of the 16-item version was good, with Chronbach’s α = 0.84. A cutoff of 7 or more items marked as true, showed good sensitivity (.85) and acceptable specificity (.42). Half (51.3%) of the above cutoff sample were classified by the Comprehensive Assessment of At-Risk Mental States (CAARMS) assessment as having Ultra-High Risk (UHR) status or as having reached the psychosis threshold. Choosing a higher cutoff of 8 produces less false positives, but also loses 8% false negatives. Differentiation between boys and girls showed that the use of distress scores improved sensitivity and specificity values for girls but worsened them for boys. When a cutoff score of 7 or more items marked as true is used, the PQ-16 is a feasible instrument with acceptable screening properties for UHR and psychosis in boys and girls aged 12–17 attending a CCAP.