Background: The Work Limitations Questionnaire-25 (WLQ-25) and the Work Instability Scale for Rheumatoid Arthritis (RA-WIS) have been used to measure at-work disability related to musculoskeletal disorders. However, a recent systematic review has shown that important psychometric properties still needed to be evaluated.
Objective: The purpose of this study was to establish the validity and responsiveness of the WLQ-25 and RA-WIS in people with chronic work-related upper-extremity disorders.
Design: Two-hundred six participants with chronic upper-extremity disorders who attended a specialty clinic operated by the Workplace Safety & Insurance Board of Ontario were evaluated at their initial visit and 6 months later.
Methods: Questionnaires completed at each evaluation were: the WLQ-25, the RA-WIS, the QuickDASH, the pain subscale of the Shoulder Pain and Disability Questionnaire, and the Chronic Pain Grade Questionnaire. At the 6-month evaluation, participants completed a global rating of change question. Known-group and construct convergent validity were assessed using analysis of variance and Pearson correlations, and standardized response means (SRMs) were used to assess responsiveness. Clinically important differences (CIDs) also were determined.
Results: The WLQ-25 and RA-WIS had low to moderate correlations with pain and disability scales (.28<r<.62) and discriminated among different functional categories (P<.001). For improved participants, the WLQ-25 (SRM=0.65 for summed score, SRM=0.63 for index score) and the RA-WIS (SRM=0.66) demonstrated moderate responsiveness. The CID for improvement was estimated to be 13/100 points for the WLQ-25 summed score, 5/28.6 points for the WLQ-25 index score, and 4/23 points for the RA-WIS.
Limitations: The external criterion of change was specific to change in upper-extremity condition and not to change in work ability or productivity.
Conclusions: The WLQ-25 and RA-WIS provide different information from that provided by pain and disability measures. They discriminate among functional outcome subgroups and detect improvement over time in people with chronic work-related upper-extremity disorders.