Factor structure and reliability of the Alzheimer's Disease Assessment Scale in a multicenter trial with linopirdine

The Alzheimer's Disease Assessment Scale (ADAS) has assumed a primary role in assessment of treatment responses in large-scale multicenter trials of drugs being evaluated for treatment of dementia in elderly patients. Data from 280 patients with Alzheimer's disease were analyzed to evaluate factor structure and reliability. Results confirm the presence of three primary factors interpreted as mental status, verbal fluency, and praxis. The presence of a large general factor underlying those more specific dimensions also supports the utility of the composite ADAS cognitive score that has been used as a primary outcome measure in previous drug trials. Test-retest reliability of the factor scores were calculated to be 0.83, 0.78, and 0.87. Test-retest reliability of the composite ADAS cognitive score was 0.90. Statistics useful for estimation of sample sizes for future multicenter trials are provided.