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

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.