Assessing Stigma in Multiple Sclerosis: Psychometric Properties of the Eight-Item Stigma Scale for Chronic Illness (SSCI-8).

BACKGROUND: The stigma associated with neurologic disorders plays a part in poor health-related quality of life. The eight-item Stigma Scale for Chronic Illness (SSCI-8) is a brief self-assessment tool for measuring perceived level of stigma. The psychometric performance of the SSCI-8 in people with multiple sclerosis (MS) was assessed.
METHODS: A multicenter, cross-sectional study in adults with relapsing-remitting or primary progressive MS was performed. A nonparametric item response theory procedure, Mokken analysis, was done to preliminarily study the dimensional structure of the SSCI-8. A confirmatory factor analysis (CFA) model was then fit, and the behavior and information covered by the eight items were assessed by parametric item response theory analysis.
RESULTS: A total of 201 patients (mean ± SD age, 43.9 ± 10.5 years; 60.2% female; 86.1% with relapsing-remitting MS) were studied. The Mokken analysis found that the SSCI-8 is a unidimensional strong scale (scalability index H = 0.56) with high reliability (Cronbach α = 0.88). The CFA model confirmed the unidimensionality (comparative fit index = 0.975, root mean square error of approximation = 0.077). The information covered by the SSCI-8 items ranges from 3.79 to 13.52, for a total of 66.56. More than half (66%) of the SSCI-8 overall information is conveyed by four items: 1 ("Some people avoided me"), 2 ("I felt left out of things"), 3 ("People avoided looking at me"), and 7 ("People were unkind to me").
CONCLUSIONS: The SSCI-8 shows appropriate psychometric characteristics and is, therefore, a useful instrument for assessing stigma in people with MS.