Interrater reliability of the Clinical Dementia Rating in a multicenter trial.

To test the interrater reliability of the Clinical Dementia Rating (CDR) in a multicenter clinical trial. Observational study. Training session for a multicenter trial of milameline, a direct muscarinic agonist, in the treatment of Alzheimer's disease. Twenty-four raters (physicians and nurses) familiar with drug trials and expert in the care of patients with Alzheimer's disease. Independent scoring of the CDR using four videotaped CDR interviews. Interrater reliability, as tested by the Kappa statistic The overall interrater reliability was 0.62. Within the CDR domains, the global kappas ranged from 0.33 +/- 0.06 to 0.88 +/- 0.06. The data support moderate to high overall interrater reliability but show important difficulties in the reliable assessment of early dementia.