An empirical comparison of diagnoses and reliabilities in ICD-10 and DSM-III-R

The psychiatric classification systems ICD-10 and DSM-III-R were compared by applying both sets of diagnostic criteria to the same sample of patients suffering from affective and psychotic disorders. Four independent raters assessed diagnoses according to both systems to 100 written case records which had been prepared in a traditional, standard format. The International Diagnostic Checklists (IDCL) were employed to rate relevant psychopathological signs and symptoms and to apply diagnostic decision rules. The results showed that ICD-10 yielded a generally higher reliability for all main disorders except for bipolar disorder. Overall reliability was kappa = 0.53 for diagnoses according to DSM-III-R and 0.59 for diagnoses according to ICD-10. Agreement was best for affective disorders, moderate for schizophrenia and inacceptable for schizoaffective disorder. Insufficient boundaries were found in both systems between schizoaffective disorder on one side and schizophrenia and bipolar disorder on the other side. The different duration criteria for schizophrenia of six months in DSM-III-R and one month in ICD-10 tend to have considerable consequences for frequency rates of schizophrenia in a typical clinical setting.