Research has identified a syndrome conferring ultra-high risk (UHR) for psychosis, although UHR interviews require intensive staff training, time and patient burden. Previously, we developed the Prodromal Questionnaire (PQ) to screen more efficiently for UHR syndromes.This study examined the concurrent validity of the PQ against UHR status and preliminary predictive validity for later psychotic disorder.We assessed a consecutive patient sample of 408 adolescents who presented to psychiatry clinics in Helsinki, Finland, seeking mental health treatment, including 80 participants who completed the Structured Interview for Prodromal Syndromes (SIPS).A cut-off score of 18 or more positive symptoms on the PQ predicted UHR diagnoses on the SIPS with 82% sensitivity and 49% specificity. Three of 14 (21%) participants with high PQ scores and SIPS UHR diagnoses developed full psychotic disorders within 1 year.Using the PQ and SIPS together can be an efficient two-stage screening process for prodromal psychosis in mental health clinics
