Characterization of Patients with Schizophrenia and Related Psychoses: Evaluation of Different Diagnostic Procedures

BACKGROUND: We aimed at estimating the value of structured interviews, medical records and clinical diagnoses for assessing lifetime diagnosis of patients with schizophrenia. In addition, the validity of the Operational Criteria Checklist (OPCRIT) system was analysed. SAMPLING AND METHODS: Swedish patients (n = 73), diagnosed with schizophrenia and related disorders by their treating physician, were scrutinized. Independent research diagnoses according to the Diagnostic and Statistical Manual, ed. 3, revised (DSM-III-R) were obtained by (1) a structured interview; (2) the OPCRIT algorithm, based on record analysis only; (3) the OPCRIT algorithm, based on record and interview analysis, or (4) a separate traditional research diagnosis based on both record and interview analysis. In addition, clinical International Classification of Diseases (ICD) diagnoses, given by the treating physician, were obtained from the case notes. Concordance rates for the different psychosis diagnoses were calculated. RESULTS: Diagnoses based on interviews only showed poor to fair agreement with the other research diagnoses, but patients diagnosed with schizophrenia or schizophrenic psychoses (i.e. schizophrenia, schizophreniform or schizoaffective disorder) at the interview almost always also obtained a corresponding research diagnosis based on record or combined sources. Diagnoses based on records only showed a good to excellent agreement with diagnoses based on records and interviews. Clinical ICD diagnoses generally displayed poor agreement with the research diagnoses, but 94% of patients ever given a clinical ICD diagnosis of schizophrenic psychosis received a corresponding traditional research diagnosis. OPCRIT diagnoses and independently assigned research diagnoses, based on the same information, displayed excellent concordance. CONCLUSIONS: Structured interviews performed with Swedish long-term-treated psychosis patients during non-hospitalization are a poor source for the evaluation of psychosis diagnoses, but a good screening instrument for the detection of DSM-III-R schizophrenia. In the investigated population, medical records are a valuable source for diagnostic assessment of psychoses and may serve as a stand-alone procedure in this patient category. Swedish clinical ICD diagnoses have a high positive predictive power identifying DSM-III-R diagnoses of schizophrenic psychoses, indicating validity of register-based research focusing on these diagnoses. The OPCRIT system is a valid tool for assessing DSM-III-R psychosis diagnoses. It should be emphasized that the present conclusions are based on the investigated Swedish psychosis population and cannot be generalized to populations composed of other patient groups or sampled in other settings, with other traditions regarding the use and availability of medical records.