Assessing Stigma in Multiple Sclerosis: Psychometric Properties of the SSCI-8 Questionnaire

Background: The stigma associated with neurologic disorders contributes to poor health-related quality of life. The 8-item Stigma Scale for Chronic Illness (SSCI-8) is a brief self-assessment tool for measuring the perceived level of stigma. The objective was to assess the psychometric performance of the SSCI-8 in people with multiple sclerosis (MS). Methods: A multicenter, cross-sectional study in subjects with relapsing-remitting or primary-progressive MS was conducted. A non-parametric item response theory (IRT) procedure, Mokken analysis, was conducted to preliminarily assess the dimensional structure of the SSCI-8. A confirmatory factor analysis (CFA) model was then fit, and finally the behavior and information covered by the 8 items were assessed by parametric IRT analysis. Results: A total of 201 subjects were studied (mean age = 43.9 ± 10.5 years, 60.2% female, 86.1% with relapsing-remitting MS). The Mokken analysis found that the SSCI-8 is a unidimensional strong scale (scalability index H = 0.56...