Administration and scoring variance on the ADAS-Cog.

The Alzheimer's Disease Assessment Scale - Cognitive (ADAS-Cog) is the most commonly used primary outcome instrument in clinical trials for treatments of dementia. Variations in forms, administration procedures and scoring rules, along with rater turnover and intra-rater drift may decrease the reliability of the instrument. A survey of possible variations in the ADAS-Cog was administered to 26 volunteer raters at a clinical trials meeting. Results indicate notable protocol variations in the forms used, administration procedures, and scoring rules. Since change over time is used to determine treatment effect in clinical trials, standardizing the instrument's ambiguities and addressing common problems will greatly increase the instrument's reliability and thereby enhance its sensitivity to treatment effects.