Validity and reliability of the Swedish version of the Self-Efficacy for Managing Chronic Disease scale for individuals with systemic sclerosis.

Abstract

Objective: To investigate aspects of validity and reliability of the Swedish version of the Self-Efficacy for Managing Chronic Disease (SEMCD-Swe) scale in systemic sclerosis (SSc).

Method: A forward-backward translation procedure was used. Content validity was assessed through interviews with 11 people with SSc and 10 healthcare professionals. Construct validity, internal consistency, test-retest reliability, and floor and ceiling effects were evaluated in 104 SSc patients.

Results: The content validity of the SEMCD-Swe was interpreted as satisfactory, but some adjustments were made to increase the understanding. Confirmatory factor analysis supported a single-factor structure. Moderate to strong correlations between the SEMCD-Swe and Scleroderma Health Assessment Questionnaire; Multidimensional Assessment of Fatigue; Patient Health Questionnaire-8 (r_s = -0.4 to -0.7), and RAND-36 subscales (r_s = 0.5 to 0.7) were found. Weak correlations were found between SEMCD-Swe and modified Rodnan skin score; and disease severity of peripheral vascular and lung (r_s = -0.1 to -0.2) and kidney (r_s = 0.1) systems (Medsger severity scale). Cronbach's alpha was sufficient (0.85) and corrected item-to-total correlations were good (≥ 0.50). The intraclass correlation coefficient for the total score was sufficient (0.82). No floor or ceiling effects were found.

Conclusion: Support for construct validity was indicated, as the SEMCD-Swe in SSc show a single-factor structure and is more strongly associated with pain, fatigue, depressive symptoms, interferences with daily activities, disability, and quality of life than with disease severity. Our results also indicate support for content validity and reliability. However, the responsiveness of the SEMCD-Swe needs to be tested.