Cross-cultural validity of the animated activity questionnaire (AAQ) that assesses activity limitations in patients with hip or knee osteoarthritis

Background: The Animated Activity Questionnaire (AAQ) measures activity limitations in hip and knee osteoarthritis (HKOA), and demonstrated good validity and reliability [1]. The AAQ shows stylized video animations of different levels of activity performance. Patients are asked to choose which video best matches their own performance. Accordingly, for international studies, the AAQ should show minimal Differential Item Functioning (DIF) across countries, which means that patients from different countries with the same level of activity limitations should have the same score on each item. Objectives: To evaluate cross-cultural validity of the AAQ. Methods: In 7 European countries patients were asked to complete the AAQ. An example of an item of the AAQ is shown on: http://kmin-vumc.nl/-14-0.html. Ordinal logistic regression was used to evaluate DIF across languages (Dutch versus 6 other languages). As a criterion for uniform DIF we used an odds ratio outside the interval 0.53-1.89. An significant interaction term (p-value