Reliability of the Italian version of the Brief (21-item) Prodromal Questionnaire (IPQ-B) for psychosis risk screening in a young help-seeking population

Objective Among current screeners for psychosis-risk mental states, the Prodromal Questionnaire- Brief (21 items) (PQ-B) is used. We aimed to assess reliability of the Italian version of the PQ-B in a young help-seeking sample. Methods - We included 151 individuals, aged 13-35 years, 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-B (iPQ-B) and were subsequently evaluated with the Comprehensive Assessment of At-Risk Mental States (CAARMS). We examined test-retest reliability, internal consistency and diagnostic accuracy (i.e. sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios) between PQ-B and CAARMS UHR-defined criteria using coefficient of stability (k), Cronbach's alpha and Cohen's kappa, respectively. Results The iPQ-B showed excellent short term test-retest reliability (k = 0.891), high internal consistency (α = 0.876) and acceptable diagnostic accuracy (sensitivity = 91.4% at the proposed cut-off of ≥ 6 on total distress score). Conclusions Psychometric properties of the iPQ-B were satisfactory. The iPQ-B is a suitable screening tool for routine use in mental health care services. Indeed, it is short and therefore easy to implement in routine assessment of early psychosis.