Comprehensive Evaluation of the Functional Activities Questionnaire (FAQ) and Its Reliability and Validity.

The Functional Activities Questionnaire (FAQ) is a collateral-report measure of difficulties in activities of daily living. Despite its widespread use, psychometric analyses have been limited in scope, piecemeal across samples, and limited primarily to classical test theory. This article consolidated and expanded psychometric analyses using tools from generalizability and item response theories among 27,916 individuals from the National Alzheimer's Coordinating Center database who completed the FAQ. Reliability was evaluated with internal consistency, test-retest, and generalizability analyses. Validity was assessed via convergence with neurocognitive measures, classification accuracy with impairment stage, and confirmatory factor and item response theory analyses. Demographics did not impact scores and there was strong evidence for reliability (0.52-0.95), though coefficients were attenuated when restricted in range to diagnostic groups (e.g., normal cognition). There were strong correlations with neurocognitive measures (rs: -.30 to -.59), strong classification accuracy (areas under the curve: .81-.99), and a single-factor model had excellent fit. All items evidenced strong item response theory discrimination and provided significant information regarding functional disability, albeit within a relatively restricted range. The FAQ is a reliable and valid measure of activities of daily living concerns for use in clinical/research settings. It best assesses mild levels of functional difficulty, which is helpful in distinguishing normal cognition from mild cognitive impairment and dementia.