Effects of rivastigmine transdermal patch and capsule on aspects of clinical global impression of change in Alzheimer's disease: a retrospective analysis.

Background: The Alzheimer's Disease Cooperative Study-Clinical Global Impression of Change (ADCS-CGIC) scale is widely used in Alzheimer trials. It assesses cognition, activities of daily living (ADLs), behavior and global functioning. To advance the understanding of relationships between the ADCS-CGIC and scores from other commonly used tools, this analysis investigated the ability of each domain to measure change. This was a hypothesis-forming study, designed to provide a basis for possible future research.

Methods: This retrospective analysis used data from a 24-week, randomized, placebo-controlled trial [study ENA713D2320 (IDEAL)] that evaluated rivastigmine patches and capsules in AD patients.

Results: At week 24, significant treatment effects versus placebo were seen on the ADCS-CGIC cognitive domain with rivastigmine 17.4 mg/24 h patch (p < 0.01), 9.5 mg/24 h patch (p = 0.02) and capsules (p < 0.01); similarly on the ADCS-CGIC ADL domain. The cognition portion of the CGIC correlated with the Alzheimer's Disease Assessment Scale cognitive subscale and the ADL section with the ADCS-ADL trial measures. Variance ascribable to these tools was small, indicating that CGIC detects changes not measured by the domain-specific tools.

Conclusions: The results of this post hoc analysis suggest that the ADCS-CGIC accurately reflects changes in cognitive and functional domains measured by other tools; it captures changes not assessed by domain-specific instruments. Cognitive alterations show greatest correlation with total CGIC. These results may assist in analyzing and interpreting CGIC results in other trials.