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.