A multicenter evaluation of new treatment efficacy instruments for Alzheimer's disease clinical trials: overview and general results. The Alzheimer's Disease Cooperative Study.

Evaluating treatment efficacy in Alzheimer's disease (AD) clinical trials requires optimal assessment methods to determine the extent and clinical meaningfulness of potential therapeutic effects of pharmacologic agents. Development of improved outcome measures for AD clinical trials is a major objective of the Alzheimer's Disease Cooperative Study (ADCS), an NIA-sponsored, multisite clinical trials consortium. The ADCS Instrument Development Project evaluated the sensitivity, reliability and validity of new or improved measures in each of five assessment domains: (a) cognition (immediate and delayed memory, praxis, attention, and executive function); (b) clinical global change; (c) activities of daily living; (d) behavioral symptoms (agitation and other noncognitive symptoms); and (e) cognition in severely impaired patients. A total of 306 English-speaking subjects were enrolled in the study, including AD patients stratified by disease severity and cognitively normal, age-matched elderly subjects. Half were retested at 1 month and 2 months after baseline, and all received 6- and 12-month follow-up assessments. Spanish versions of these new measures are currently being evaluated. The development of this multisite study, the common methods and procedures, and a detailed description of the cohort are provided in this overview article. This multisite project demonstrates the feasibility of a consortium approach to instrument development. We were able to develop new instruments and efficiently evaluate their reliability and sensitivity to longitudinal change by capitalizing on the experience and patient resources of the participating ADCS research sites.