Evaluation of the Coping Strategies Questionnaire-Revised for fatigue in systemic sclerosis: a Scleroderma Patient-centred Intervention Network (SPIN) cohort study.

OBJECTIVES: To adapt and evaluate the Coping Strategies Questionnaire-Revised (CSQ-R), designed to assess pain coping, for assessing coping with fatigue in systemic sclerosis (SSc). METHODS: We adapted CSQ-R items for fatigue, and a panel of people with SSc verified content validity. Scleroderma Patient-centred Intervention Network Cohort participants completed the CSQ-R-Fatigue. We evaluated factor structure with confirmatory factor analysis (CFA), assessed differential item functioning (DIF) by English and French language and disease subtype, and evaluated internal consistency and test-retest reliability. RESULTS: 863 participants were included. Most were female (n=756; 88%), and 36% (n=308) had diffuse SSc. We replicated the 6-factor CSQ-R structure (Tucker-Lewis Index =0.95, Comparative Fit Index =0.97, Root Mean Square Error of Approximation =0.05). We found substantive DIF across multiple factors, however, for language and disease subtype (11 items on 6 factors for language, 10 items on 5 factors for subtype). Factor-score differences due to DIF by language and subtype were ≥0.20 standardised mean differences for 4 factors each. Test-retest reliability for factors based on intraclass correlation was between 0.68 [95% CI 0.58, 0.76] and 0.91 [95% CI 0.88, 0.93]; n=183. CONCLUSIONS: The CSQ-R-Fatigue may not be appropriate to assess coping with fatigue in SSc due to possible biases related to language and disease severity. An additional concern is that the CSQ-R-Fatigue focuses on psychological coping and does not assess active coping strategies. Research is needed to identify or develop tools to evaluate coping strategies for managing fatigue in SSc.