Performance-based and Observational Assessments in Clinical Trials Across the Alzheimer's Disease Spectrum.

Assessment of the earlier stages of Alzheimer's disease requires different strategies than those previously developed for fully syndromal Alzheimer's disease . This challenge is further magnified in very early stages, where symptomatology may be minimal and functional deficits very subtle to absent. This paper reviews strategies for performance-based assessment of the early stages of Alzheimer's disease, including assessments of cognition, functional capacity, and social cognition. Meetings with an International Society for CNS Clinical Trials and Methodology working group served as the basis for this paper and its companion. The current state of the art of detection and staging-oriented assessments is presented, and information is provided regarding the practicality and validity of these approaches, with a special focus on their usefulness in clinical trials for new medication development.