Linguistic validation, validity, and reliability of the British English version of the Workplace Activity Limitations Scale in employed people with rheumatoid arthritis, ankylosing spondyloarthritis, osteoarthritis and fibromyalgia .

Abstract

Abstract Purpose: The Workplace Activity Limitations Scale (WALS) is a patient reported outcome measure of work ability developed in Canada for use in arthritis. The aims of this study were to linguistically validate a British English version of the WALS, and then psychometrically test this in rheumatoid arthritis (RA), ankylosing spondyloarthritis (AS), osteoarthritis (OA) and fibromyalgia (FM).Methods: Phase 1: The WALS was forward translated, reviewed by an expert panel and cognitive debriefing interviews conducted. Phase 2: Participants completed a postal questionnaire booklet. Construct validity was examined by fit to the Rasch measurement model. Concurrent validity included testing between the WALS and the Work Limitations Questionnaire-25 (WLQ-25). Two weeks later, participants were mailed a second questionnaire booklet for test-retest reliability. Results: Phase 1: Minor wording changes were made. Phase 2: 831 employed participants completed questionnaires: 267 men; 564 women; 53.5 (SD 8.9) years of age; with condition duration 7.7 (SD 8.0) years. The WALS satisfied Rasch model requirements when implemented in a bi-actor equivalent solution. A WALS Rasch transformation table was created. Concurrent validity was strong with the: WLQ-25 (RA rs = 0.78; AS rs = 0.83; OA rs = 0.63; FM rs = 0.64). Internal consistency was consistent with group use (α = 0.80 to 0.87). Test-retest reliability was excellent (ICC (2,1) at 0.90 or above. Conclusions: A reliable, valid British English version of the WALS is now available for use in the United Kingdom.