McLean-Harvard International First-Episode Project: two-year stability of ICD-10 diagnoses in 500 first-episode psychotic disorder patients.

OBJECTIVE

Because clinical and biologic research and optimal clinical practice require stability of diagnoses over time, we determined stability of ICD-10 psychotic disorder diagnoses and sought predictors of diagnostic instability.

METHOD

Patients from the McLean-Harvard International First-Episode Project, conducted from 1989 to 2003, who were hospitalized for first psychotic illnesses (N = 500) were diagnosed by ICD-10 criteria at baseline and 24 months, on the basis of extensive prospective assessments, to evaluate the longitudinal stability of specific categorical diagnoses and predictors of diagnostic change.

RESULTS

Diagnostic stability averaged 90.4%, ranking as follows: schizoaffective disorder (100.0%) > mania with psychosis (99.0%) > mixed affective episode (94.9%) > schizophrenia (94.6%) > delusional disorder (88.2%) > severe depressive episode with psychotic symptoms (85.2%) > acute psychosis with/without schizophrenia symptoms = unspecified psychosis (all 66.7%) >> acute schizophrenia-like psychosis (28.6%). Diagnoses changed by 24 months of follow-up to schizoaffective disorder (37.5%), bipolar disorder (25.0%), schizophrenia (16.7%), or unspecified nonorganic psychosis (8.3%), mainly through emerging affective features. By logistic regression, diagnostic change was associated with Schneiderian first-rank psychotic symptoms at intake > lack of premorbid substance use.

CONCLUSIONS

We found some psychotic disorder diagnoses to be more stable by ICD-10 than DSM-IV criteria in the same patients, with implications for revisions of both diagnostic systems.