The study aims to establish the concordant validity of the Early Detection Primary Care Checklist (PCCL); a 20 item tool designed to help primary care practitioners identify young people in the early stages of psychosis. The checklist was completed by the referring practitioners of 176 young people referred to early detection teams across the UK. The concordant validity of the checklist was established by comparing screen results with a standardised psychiatric assessment for identifying young people who may be at a risk of developing psychosis (CAARMS). Preliminary analysis found that the simple checklist as originally conceived had excellent sensitivity (96%) but poor specificity (10%). Subsequent exploratory analysis led to the development of two better performing models for the combination of item responses to predict CAARMS outcomes. The first retained the use of all 20 checklist items and achieved sensitivity of 89% and specificity of 60%. The second retained six checklist items with p-values of 0.2 or above and achieved sensitivity of 88% and specificity of 47%. Although the initial checklist did not perform well as a screening tool the two models perform well in comparison to other, much longer, screening tools for this population. These tools are not intended as a diagnostic instrument; rather it has been designed as a bridge between primary care and specialist services and to build on the skills and knowledge already held by primary care practitioners. Following a consideration of the limitations of this study, the continued evaluation of the tools performance in practice is recommended.
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