The ICD-10 clinical field trial for mental and behavioral disorders: results in Canada and the United States

OBJECTIVE: To help evaluate the impact of proposed revisions to the chapter on mental and behavioral disorders for ICD-10, the World Health Organization (WHO) Division of Mental Health organized an international clinical field trial to evaluate draft clinical descriptions and diagnostic guidelines. The authors compare interrater diagnostic reliability results from this field trial for clinicians in Canada and the United States of American with those from all other clinicians worldwide, as well as with those from field trials conducted to evaluate drafts of DSM-III. METHOD: Two or more clinicians at each clinical center independently evaluated each patient, following a study protocol that allowed clinicians to list up to six diagnoses. In Canada and the United States, 96 clinicians completed 1,781 assessments among 491 patients, and elsewhere in the world 472 clinicians completed 7,495 assessments among 1,969 patients. RESULTS: Summary kappa coefficients at two-, three-, and four-character ICD-10 code levels were 0.76, 0.65, and 0.52, respectively, for Canadian and U.S. clinicians and 0.83, 0.75, and 0.62 for clinicians elsewhere. The mean number of diagnoses per assessment for Canadian and U.S. clinicians was 2.1; for clinicians elsewhere it was 1.7. More multiple coding of diagnoses for substance use disorders, mood (affective) disorders, and personality disorders by Canadian and U.S. clinicians accounted for much of the difference in diagnostic coding and in interrater reliability between them and clinicians elsewhere. CONCLUSIONS: Interrater diagnostic reliability in Canada and the United States was similar to that of clinicians worldwide and also to results from the DSM-III field tests. Use of more multiple coding of selected disorders by Canadian and U.S. clinicians may reflect the influence of DSM-III and DSM-III-R, which encourage multiple diagnostic entries and the use of separate multiaxial coding for personality disorders, and may have reduced interrater concurrence for some categories. Further, collaborative development of ICD-10 with DSM-IV has aligned these two systems more closely.