Congruence of diagnoses 2 years after a first-admission diagnosis of psychosis

Background: Diagnostic changes may reflect evolution of an illness, emergen ce of newly disclosed information, or unreliability of assessment. This stu dy evaluates the stability of research diagnoses in a heterogeneous first-a dmission sample with psychosis. Methods: A group of 547 subjects initially diagnosed with a psychosis were reassessed 6 and 24 months after enrollment. The DSM-IV consensus diagnoses were formulated by psychiatrists blind to previous research diagnoses. The analysis focuses on agreement over time and the effects of demographic, fa mily history, and clinical variables on the shift from a nonschizophrenia d iagnosis to schizophrenia. Results: Seventy-two percent of 6- and 24-month diagnoses were congruent. T he most temporally consistent 6-month categories were schizophrenia (92%), bipolar disorder (83%), and major depression (74%); the least stable were p sychosis not otherwise specified (44%), schizoaffective disorder (36%), and brief psychosis (27%). The most frequent shift in diagnosis at 24 months w as to schizophrenia spectrum (n=45). These 45 subjects had a similar illnes s course after 6 months as the 171 subjects in this category at both assess ments, but their prior clinical functioning was better. Risk factors predic ting change to a schizophrenia spectrum diagnosis include facility variable s (schizophrenia diagnosis, longer stays, and given antipsychotic medicatio n on hospital discharge); prehospital features (psychotic greater than or e qual to 3 months before admission, poorer adolescent adjustment, lifetime s ubstance disorder); and negative symptoms. Conclusions: Changes in diagnosis, particularly to schizophrenia, are mostl y attributable to the evolution of the illness. Rigid adherence to DSM-IV r equirements may have led to underdiagnosis of schizophrenia. The findings s upport the need for a longitudinally based diagnostic process in incidence samples.