Psychometric testing of the British English Workplace Activity Limitations Scale in four rheumatic and musculoskeletal conditions

Objectives: The aims were to linguistically validate a British English version of the Workplace Activity Limitations Scale (WALS), and then psychometrically test this in rheumatoid arthritis (RA), axial spondyloarthritis (axSpA), osteoarthritis (OA) and fibromyalgia (FM).
Methods: The WALS was forward translated, reviewed by an expert panel and cognitive debriefing interviews conducted. Participants completed a postal questionnaire booklet. Construct (structural) 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: Minor wording changes were made to the WALS, then 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 and a WALS Rasch transformation table was created. Concurrent validity was strong with the: WLQ-25 (RA rs = 0.78; axSpA 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.

Conclusion: A reliable, valid British English version of the WALS is now available for use in the United Kingdom.