Psychometric testing of the British English Long-Term Conditions Job Strain Scale, Long-Term Conditions Work Spillover Scale and Work-Health-Personal Life Perceptions Scale in four rheumatic and musculoskeletal conditions

OBJECTIVE: The aims were to validate linguistically British-English versions of the Long-Term Conditions Job Strain Scale (LTCJSS), Long-Term Conditions Work Spillover Scale (LTCWSS) and Work-Health-Personal Life Perceptions Scale (WHPLPS) in rheumatoid arthritis, axial spondyloarthritis, osteoarthritis and fibromyalgia (FM). METHODS: The three scales were forward translated and reviewed by an expert panel prior to cognitive debriefing interviews. Participants completed a postal questionnaire. Construct validity was assessed using Rasch analysis. Concurrent validity included testing between the three scales and work (e.g., Workplace Activity Limitations Scale [WALS]) and condition-specific health scales. Two weeks later, participants were mailed a second questionnaire to measure test-retest reliability. RESULTS: The questionnaire was completed by 831 employed participants: 68% women, 53.5 (SD 8.9) years of age, with condition duration 7.7 (SD 8.0) years. The LTCJSS, LTCWSS and WHPLPS Parts 1 and 2 satisfied Rasch model requirements, but Part 3 did not. A Rasch transformation scale and Reference Metric equating scales with the WALS were created. Concurrent validity was generally good (r(s) = 0.41-0.85) for the three scales, except the WHPLPS Part 3. Internal consistency (Person Separation Index values) was consistent with group use in all conditions, and individual use except for the LTCWSS and WHPLSP Parts 1 and 2 in FM. Test-retest reliability was excellent, with intraclass coefficients (2,1) of 0.80-0.96 for the three scales in the four conditions. DISCUSSION: Reliable, valid versions of the British-English LTCJSS, LTCWSS and WHPLPS Parts 1 and 2 are now available for use in the UK