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Published on: October 13, 2016
Agreement in cognitive and clinical assessments in Alzheimer's disease
Rochelle E Tractenberg1, Paul S Aisen
1Departments of Neurology, Biostatistics, Bioinformatics and Biomathematics, and Psychiatry, Georgetown University School of Medicine, Washington, D.C. 20057, USA. ret7@georgetown.edu
Aims:
To estimate agreement among scores on three common assessments of cognitive function.
Method:
Baseline responses on the Alzheimer's Disease Assessment Scale - Cognitive, Clinical Dementia Rating, and the Mini-Mental State Examination were obtained from two clinical trials (n = 138 and n = 351). A graphical method of examining agreement, the means-difference or Bland-Altman plot, was followed by Levene's test of the equality of variance corrected for multiple comparison within each sample.
Results:
70-78% of variability was shared by one factor, suggesting that all three instruments reflect cognitive impairment. However, agreement among tests was significantly worse for individuals with greater-than-average, relative to individuals with less-than-average, cognitive impairment.
Conclusions:
Worse agreement between tests, as a function of increasing cognitive impairment, implies that interpretation of these tests and selection of coprimary cognitive impairment outcomes may depend on impairment level.
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