Coding guidelines for ICD-9 section on mental disorders and reliability of chart clinical diagnoses

A major innovation of the ICD-10 draft is provision of diagnostic guidelines. This is assumed to be appropriate for use in clinical situations. In Norway a similar approach was adopted when ICD-9 was introduced as the official classification system in 1987. This was done in order to avoid national diagnostic bias and increase diagnostic reliability. A comparison with the DSM-III criteria was included in the diagnostic guidelines. The effectiveness of this approach was investigated by comparing the chart ICD-9 diagnoses of 104 psychiatric in- and outpatients from 2 teaching hospitals with the diagnoses obtained by using case record rating forms (criterion diagnosis). According to the criterion diagnoses, the base rate of chart diagnoses of schizophrenia and manic-depressive psychosis was too low, and the base rate of reactive psychosis too high. Several chart diagnoses proved to have low reliability, particularly reactive psychosis, paranoid psychosis, depressive neurosis and personality disorders. The study suggests that the provision of extensive diagnostic guidelines does not necessarily alter previous diagnostic practice. Reasons for these findings and the implications for the ICD-10 diagnostic criteria and diagnostic guidelines are discussed.