The Italian version of the 92-item Prodromal Questionnaire: Concurrent validity with the SIPS and factor analysis in a sample of 258 outpatients aged 11–36 years

Background Current early screeners for psychosis-risk states have still to prove ability in identifying at-risk individuals. Among screeners, the 92-item Prodromal Questionnaire (PQ-92) is often used. We aimed to assess the validity of its Italian translation in a large Italian adolescent and young adult help-seeking sample. Methods We included all individuals aged 12–36 years seeking help at psychiatric mental health services in a large semirural Roman area (534,600 population) who accepted to participate. Participants completed the Italian version of the PQ-92 and were subsequently assessed with the Structured Interview of Prodromal/Psychosis-Risk Syndromes (SIPS). We examined diagnostic accuracy (sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios) and content, concurrent, and convergent validity between PQ-92 and SIPS using Cronbach's alpha, Cohen's kappa, and Spearman's rho, respectively. We tested the validity of adopted cut-offs through Receiver Operating Characteristic (ROC) curves plotted against SIPS diagnoses and the instrument's factor-structure through Principal Component Analysis. Results PQ-92 showed high internal consistency, acceptable diagnostic accuracy and concurrent validity, and excellent convergent validity. ROC analyses pointed to scores of 18 on the Positive subscale and 36 on the total PQ-92 as best cut-offs. The Scree-test identified a four-factor solution as fitting best. Conclusions Psychometric properties of Italian PQ-92 were satisfactory. Optimal cut-offs were confirmed at ≥ 18 on the positive subscale, but at ≥ 36 on the total scale was able to identify more SIPS-positive cases.