Validation of the Swedish version of PROMIS-29v2 and FACIT-Dyspnea Index in patients with systemic sclerosis

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Purpose To evaluate the reliability, internal consistency, and construct validity of the Swedish versions of PROMIS-29 and Functional Assessment of Chronic Illness Therapy-Dyspnea (FACIT-Dyspnea) instruments in patients with systemic sclerosis (SSc). Methods In a cross-sectional study, consecutive SSc patients completed a paper-based survey. Internal consistency was assessed using Cronbach’s alpha. Test–retest reliability was tested employing weighted Kappa (K w) and intra-class correlation coefficient (ICC). Construct validity was evaluated by hypotheses testing using RAND-36, MRC Dyspnea score, Scleroderma Health Assessment Questionnaire (SHAQ) and clinical measurements. Results Forty-nine patients (86% female; 73% limited cutaneous SSc) completed the survey. The mean disease duration was 11 years and mean SHAQ was 0.5. Internal consistency and test–retest reliability were good with the exception of PROMIS-29 anxiety. PROMIS-29, FACIT-Dyspnea, and Functional limitation showed strong correlations to corresponding RAND-36 domains (|r s|=0.67 to −0.85). Relevant PROMIS-29 domains, FACIT-Dyspnea and Functional limitation correlated strongly to SHAQ and VAS overall disease severity (|r s|=0.60 to −0.75). Ceiling effects (>15%) were found in six PROMIS-29 domains and in both FACIT-Dyspnea and Functional limitations. Four (4/5) hypotheses were confirmed. Conclusions PROMIS-29 and FACIT-Dyspnea meet the requirements for reliability and have adequate construct validity in Swedish patients with SSc. Implications for rehabilitation PROMIS-29v2 and Functional Assessment of Chronic Illness Therapy-Dyspnea (FACIT-Dyspnea) Index are patient outcome measures that gain increasing interest for the evaluation of patient with rheumatologic diseases. PROMIS-29v2 and FACIT-Dyspnea Index meet the requirements for reliability and have adequate construct validity compared to legacy measures in Swedish patients with systemic sclerosis. Translation and validation of PROMs is important for studies of rare diseases in multi-center collaborations.