Psychometric testing of the British English workplace activity limitations Scale in four rheumatic and musculoskeletal conditions

Objectives

The aims were to validate a British English version of the Workplace Activity Limitations Scale (WALS) linguistically, then test this psychometrically in RA, axial spondyloarthritis (axSpA), OA and FM.

Methods

The WALS was forward translated, reviewed by an expert panel, and cognitive debriefing interviews were 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 and 564 women; 53.5 (s.d. 8.9) years of age; with condition duration 7.7 (s.d. 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 r _s = 0.78; axSpA r _s = 0.83; OA r _s = 0.63; FM r _s = 0.64). Internal consistency was consistent with group use (α = 0.80-0.87). Test-retest reliability was excellent, with intraclass correlation coefficient (2,1) at ≥0.90.

Conclusion

A reliable, valid British English version of the WALS is now available for use in the UK.