CROSS-NATIONAL INTERRATER AGREEMENT ON THE CLINICAL DIAGNOSTIC-CRITERIA FOR DEMENTIA

We assessed the interobserver agreement on the clinical diagnosis of d ementia syndrome and dementia subtypes as part of a cross-national pro ject on the prevalence of dementia. Fourteen clinicians from the parti cipating countries (Canada, Chile, Malta, Nigeria, Spain, and the Unit ed States) independently assessed the diagnosis of 51 patients whose c linical information was in standard records written in English. We use d the DSM-III-R and ICD-10 criteria for dementia syndrome, the NINCDS- ADRDA criteria for Alzheimer's disease (AD), and the ICD-10 criteria f or other dementing diseases, and measured interobserver agreement. We found comparable levels of agreement on the diagnosis of dementia usin g the DSM-III-R (kappa = 0.67) as well as the ICD-10 criteria (kappa = 0.69). Cognitive impairment without dementia was a major source of di sagreement (kappa = 0.10). The kappa values were 0.58 for probable AD, 0.12 for possible AD, and rose to 0.72 when the two categories were m erged. The interrater reproducibility of the diagnosis of vascular dem entia was 0.66 in terms of kappa index; the diagnoses of other dementi ng disorders as a whole reached a kappa value of 0.40. This study sugg ests that clinicians from different cultures and medical traditions ca n use the DSM-III-R and the ICD-10 criteria for dementia effectively a nd thus reliably identify dementia cases in cross-national research. T he interrater agreement on the diagnosis of dementia might be improved if clear-cut guidelines in the definition of cognitive impairment are provided. To improve the reliability of AD diagnosis in epidemiologic studies, we suggest that the NINCDS-ADRDA ''probable'' and ''possible '' categories be merged.