Item response analysis of Alzheimer's Disease Assessment Scale.

Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) suffers from low sensitivity in detecting changes in Alzheimer's disease progression in clinical trials of disease-modifying treatments. A comprehensive psychometric analysis of the items in ADAS-cog assessment can help in identifying and improving the insensitive items. Item response theory provides a suitable framework for investigating the ADAS-cog items; however, it requires prior information on the underlying latent construct for reliable analysis. In this study, we perform an exploratory item response analysis to investigate the latent construct underlying the relationships between the ADAS-cog item responses. The results indicate that the underlying latent construct of ADAS-cog is multidimensional in nature with the latent factors measuring cognitive declines in several domains (such as memory, praxis, and language domains).