Reliability of the Alzheimer’s Disease Assessment Scale (ADAS-Cog) in longitudinal Studies

Author(s): Anzalee Khan, Christian Yavorsky, Guillermo DiClemente, Mark Opler, Stacy Liechti, Brian Rothman, Sofija Jovic.

Journal Name: Current Alzheimer Research

Volume 10 , Issue 9 , 2013

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Background: Considering the scarcity of longitudinal assessments of reliability, there is need for a more precise understanding of cognitive decline in Alzheimer’s Disease (AD). The primary goal was to assess longitudinal changes in inter-rater reliability, test retest reliability and internal consistency of scores of the ADAS-Cog.

Methods: 2,618 AD subjects were enrolled in seven randomized, double-blind, placebo-controlled, multicenter-trials from 1986 to 2009. Reliability, internal-consistency and cross-sectional analysis of ADAS-Cog and MMSE across seven visits were examined.

Results: Intra-class correlation (ICC) for ADAS-Cog was moderate to high supporting their reliability. Absolute Agreement ICCs 0.392 (Visit-7) to 0.806 (Visit-2) showed a progressive decrease in correlations across time. Item analysis revealed a decrease in item correlations, with the lowest correlations for Visit 7 for Commands (ICC=0.148), Comprehension (ICC=0.092), Spoken Language (ICC=0.044).

Discussion: Suitable assessment of AD treatments is maintained through accurate measurement of clinically significant outcomes. Targeted rater education ADAS-Cog items over-time can improve ability to administer and score the scale.

Keywords: Reliability, Alzheimer’s disease, data monitoring.

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Article Details

Year: 2013
Page: [952 - 963]
Pages: 12
DOI: 10.2174/15672050113106660160
Price: $58

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