Diagnostic stability 2 years after treatment initiation in the early psychosis intervention programme in Singapore.

OBJECTIVE: To evaluate the diagnostic stability of psychotic disorders over a 2 year period in patients presenting with first-episode psychosis.

METHODS: One hundred and fifty-four patients were recruited from an early psychosis intervention programme (EPIP). They were diagnosed by the attending psychiatrist using the Structured Clinical Interview for DSM-IV Axis I at first contact (baseline) and after 24 months. The diagnoses were classified into the following categories: schizophrenia spectrum disorders (schizophrenia, schizophreniform disorder and schizoaffective disorder), affective psychosis (bipolar and major depressive disorders with psychotic symptoms), and other non-affective psychosis (delusional disorder, psychosis not otherwise specified and brief psychotic disorder). Two measures of stability, the prospective and the retrospective consistency were determined for each diagnosis.

RESULTS: The diagnoses with the best prospective consistency were schizophrenia (87.0%) and affective psychosis (54.5%). The shift into schizophrenia spectrum disorder was the most frequent diagnostic change. Duration of untreated psychosis was found to be the only significant predictor of shift.

CONCLUSION: It is difficult to make a definitive diagnosis at first contact. The clinical need to review the diagnosis throughout the period of follow up is emphasized.