Review of outcome measurement instruments in Alzheimer's disease drug trials: Psychometric properties of global scales

The use of global outcome measures with strong psychometric properties in A lzheimer's disease (AD) drug trials is encouraged. This article focuses on Clinician Global Impression of Change scales, the Clinical Dementia Rating, and the Global Deterioration Scale to provide (1) a review of psychometric properties, (2) a critique of how these properties are assessed in the lit erature, and (3) a basis for evaluating, from the standpoint of psychometri c properties, the appropriateness of using a given global scale in a drug t rial. Reported reliability and validity estimates for the aforementioned sc ales range from fair to very good, but small sample sizes and/or inappropri ate measures of correlation weaken the quality of the evidence. There is al so a dearth of published information on responsiveness to change. Researche rs planning AD drug trials should consider these issues, along with the int erval between test administrations for test-retest reliability, to help sel ect appropriate global outcome measurement instruments.