The Evaluation of Daily Activity Questionnaire (EDAQ) is a detailed patient-reported outcome measure of activity ability. The objective of this research was to assess the linguistic and cross-cultural validity and psychometric properties of the EDAQ in rheumatoid arthritis for Dutch and German speakers. The EDAQ was translated into Dutch and German using standard methods. A total of 415 participants (Dutch n = 252; German n = 163) completed two questionnaires about four weeks apart. The first included the EDAQ, Health Assessment Questionnaire (HAQ) and 36-item Short-Form v2 (SF-36v2) and the second, the EDAQ only. We examined construct validity using Rasch analysis for the two components (Self-Care and Mobility) of the Dutch and German EDAQ. Language invariance was also tested from the English version. We examined internal consistency, concurrent and discriminant validity and test-retest reliability in the 14 EDAQ domains. The Self-Care and Mobility components satisfied Rasch model requirements for fit, unidimensionality and invariance by language. Internal consistency for all 14 domains was mostly good to excellent (Cronbach's alpha ≥ 0.80). Concurrent validity was mostly strong: HAQ rs = 0.65-0.87; SF36v2 rs = - 0.61 to - 0.87. Test-retest reliability was excellent [ICC (2,1) = 0.77-0.97]. The EDAQ has good reliability and validity in both languages. The Dutch and German versions of the EDAQ can be used as a measure of daily activity in practice and research in the Netherlands and German- speaking countries.
Keywords: Activities of daily living; Occupational therapy; Outcome assessment; Rasch analysis; Rehabilitation; Rheumatoid arthritis.