Further validation of the Multiple Sclerosis Self-Efficacy Scale

Purpose: This study examined the factorial and construct validity of the Multiple Sclerosis Self-Efficacy (MSSE) Scale in two samples of people with multiple sclerosis (MS). Method: Two samples (n's = 292, 275) of participants with MS were recruited from across the United States. Participants in both studies completed a questionnaire battery that included the MSSE and measures of symptoms, dysfunction, disability, psychosocial aspects, mental/emotional wellbeing, and quality of life. Factorial validity was tested using confirmatory factor analysis (CFA), whereas construct validity was examined based on bivariate correlations with scores from other measures. Results: The two-factor measurement model provided a poor fit for the 18 items on the MSSE in both the samples. This model provided a good fit for a modified, 10-item scale in both samples. The 10-item version of the MSSE was highly correlated with the original MSSE (r = 0.97, p<0.001) and related constructs (e.g. disability, r = 0.69, p<0.0001). The standardized Cronbach's as of the two subscales (function and control) of the 10-item version ranged between 0.78 and 0.94 for both samples. Conclusions: Scores from the modified, 10-item version of the MSSE provide a valid and reliable measure of MS-specific self-efficacy among persons with MS.