RESUMEN
AIM: Diagnosis during the initial stages of first-episode psychosis is particularly challenging but crucial in deciding on treatment. This is compounded by important differences in the two major classification systems, International Classification of Diseases, 10th revision (ICD-10) and Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). We aimed to compare the concordance between an operationalized diagnosis using Operational Criteria Checklist (OPCRIT) and treating clinician-generated diagnosis in first episode psychosis diagnosis and its correlation with treatment prescribed. METHODS: Operationalized polydiagnostic assessments were conducted on 150 first-episode psychosis patients using OPCRIT. OPCRIT generated ICD-10, DSM-IV and treating clinician diagnoses were compared. The association between these diagnoses and choice of treatment was evaluated. RESULTS: General agreement between the three classification systems was moderate to good, with kappa values between 0.460 and 0.674. There was a higher frequency of schizophrenia diagnosis in ICD-10 (n = 85) comparing to DSM-IV (n = 45) and similar in clinical diagnosis (n = 76), with moderate to good agreement between classifications (kappa between 0.602 and 0.731). No significant differences were found for ratings of psychotic depressive and manic/bipolar disorders with psychosis, with affective disorders having the higher agreement. Heterogeneous group of 'other disorders' achieved a kappa value from 0.250 (DSM-IV/ICD-10) to 0.566 (DSM-IV/clinical diagnosis). CONCLUSION: Despite the challenges in first-episode psychosis diagnosis, it is possible to have a good agreement between OPCRIT-generated (DSM-IV and ICD-10) diagnoses and clinician based diagnoses, although some differences exist. The choice of psychopharmacological treatment prescribed matches well with these operationalized diagnoses.