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P2–283: Psychometric features of the ADAS‐Cog: Identifying a potential cognition endpoint for prodromal Alzheimer's disease
Author(s) -
Hannesdottir Kristin,
Ashwood Tim,
Olsson Tina,
Sjogren Niclas,
Jaeger Judith,
Berger AnnaKarin,
Nordgren Ingrid,
Karlsson Par
Publication year - 2013
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2013.05.930
Subject(s) - alzheimer's disease neuroimaging initiative , ceiling effect , clinical trial , neuroimaging , cognition , cog , dementia , psychology , disease , medicine , psychiatry , pathology , computer science , artificial intelligence , alternative medicine
cognitive functioning for different stages of AD. Despite the popularity of the ADAS-Cog, few studies have examined its item properties among patients with Mild Cognitive Impairment (MCI) and moderate impairment, and further validation of the ADAS-Cog is needed to substantiate its use at different stages of AD. This study examined whether there are differences in response to a particular item as a function of respondent characteristics (Apolipoprotein E and Impairment level) in the ADAS-Cog.Methods: jMetrik was used to analyse the ADAS-Cog. AD data was obtained from the Critical Path Institute Online Data Repository (CODR). Separate Rasch analyses were conducted comparingApoE carriers (n1⁄4 505) vs non-carriers (n 1⁄4 507), and MCI (MMSE 1⁄4 21 to 26; n 1⁄4 1362) and Moderate impairment (MMSE 14 to 20; n 1⁄4 1211) to examine summary and individual model fit statistics, person separation index (PSI), response format, local dependency, targeting, item bias (or differential item functioning -DIF), and dimensionalityResults:Based on the results of Rasch analyses different approaches can be taken to account measurement bias in properties of the ADAS-Cog post-hoc.Lower item calibration (Delta) reflects items with bias, indicating whether subgroups respond to items differently. The average age of 74.08 years (SD1⁄4 8.15) with 55.7%male patients. Commands (Delta 1⁄4 0.23), Constant Praxis (0.26), Ideational Praxis (0.32), and Naming Objects (0.26) shows ’moderate’ DIF, favoring theModerately impaired group, indicating that this item functions better in this group. Orientation (Delta 1⁄4 1.34) shows ’Large’ DIF, favoring the Moderately impaired group, indicating that this item functions better in this group. Word Recognition (-1.38) and Word Recall (-1.20) shows ’Large’ DIF, favoring the MCI group, indicating that this item functions better in this group. Conclusions: The choices made during analysis will substantially affect the results, and we have described and illustrated that the subgroups may have different impact on different items affecting outcome.