The Italian version of the 16-item prodromal questionnaire (iPQ-16): field-test and psychometric features

OBJECTIVE: Among current early screeners for psychosis-risk states, the Prodromal Questionnaire-16 items (PQ-16) is often used. We aimed to assess validity and reliability of the Italian version of the PQ-16 in a young adult help-seeking population. METHODS: We included 154 individuals aged 18-35years seeking help at the Reggio Emilia outpatient mental health services in a large semirural catchment area (550.000 inhabitants). Participants completed the Italian version of the PQ-16 (iPQ-16) and were subsequently evaluated with the Comprehensive Assessment of At-Risk Mental States (CAARMS). We examined diagnostic accuracy (i.e. specificity, sensitivity, negative and positive likelihood ratios, and negative and positive predictive values) and content, convergent, and concurrent validity between PQ-16 and CAARMS using Cronbach's alpha, Spearman's rho, and Cohen's kappa, respectively. We also tested the validity of the adopted PQ-16 cut-offs through Receiver Operating Characteristic (ROC) curves plotted against CAARMS diagnoses and the 1-year predictive validity of the PQ-16. RESULTS: The iPQ-16 showed high internal consistency and acceptable diagnostic accuracy and concurrent validity. ROC analyses pointed to a cut-off score of ≥5 as best cut-off. After 12months of follow-up, 8.7% of participants with a PQ-16 symptom total score of ≥5 who were below the CAARMS psychosis threshold at the baseline, developed a psychotic disorder. CONCLUSIONS: Psychometric properties of the iPQ-16 were satisfactory.