Featured Articles Putting the Alzheimer's cognitive test to the test I: Traditional psychometric methods

Background: TheAlzheimer’sDiseaseAssessmentScale—CognitiveBehaviorsection(ADAS-Cog) isthemostcommonlyusedcognitivetestinADclinicaltrials.However,thereareconcernsaboutitsuse in early-stage disease. Herein we examine those concerns using traditional psychometric methods. Methods: We analyzed ADAS-Cog data (n 5 675) based on six psychometric properties: data completeness; scaling assumptions; targeting; reliability; validity; and responsiveness. Results: At the scale-level, criteria tested for data completeness, scaling assumptions (item total correlations0.33–0.59),targeting(nofloor/ceilingeffects),reliability(Cronbach’sa50.74),andvalidity (correlation with MMSE 52 0.70) were satisfied. Responsiveness (baseline to 12 months; n 5 145) wasmoderatetohigh(effectsize520.73).However,8of11ADAS-Cogcomponentshadsubstantial ceiling effects (range 32%–83%), and decreased responsiveness associated with low to moderate effect sizes (0.14–0.65). Conclusion: In our study, many patients with AD found large portions of the ADAS-Cog too easy. Future research should consider modifying the ADAS-Cog or developing a new test. 2013 The Alzheimer’s Association. All rights reserved.