Rationale for use of the Clinical Dementia Rating Sum of Boxes as a primary outcome measure for Alzheimer's disease clinical trials

Background: We used the database of the Alzheimer's Disease Neuroimaging Initiative (ADNI) to explore the psychometric properties of the Clinical Dementia Rating Sum of Boxes (CDR-SB) to consider its utility as an outcome measure for clinical trials in early and mild, as well as later, stages of Alzheimer's disease (AD). Methods: We assessed internal consistency, structural validity, convergent validity, and 2-year internal and external responsiveness of the CDR-SB using data from 382 subjects with early or mild AD at entry into the ADNI study. Results: The CDR-SB assesses both cognitive and functional domains of AD disability. Mean scores declined nearly linearly; CDR-SB cognitive and functional subsums contributed equally to total scores at both very mild (early) and mild stages of the disease. Conclusions: The CDR-SB has psychometric properties that make it attractive as a primary outcome measure that comprehensively assesses both cognitive and functional disability in AD patients. It may prove particularly useful for studies in early, predementia stages of AD. (C) 2013 The Alzheimer's Association. All rights reserved.