The unidimensional self-efficacy scale for MS (USE-MS): developing a patient based and patient reported outcome

Abstract

Background: Self-efficacy concerns the individual’s belief that he or she is capable of performing a certain task and producing a desired effect, i.e. it reflects the person’s perceptions of their capability for specific tasks, as distinct from their actual ability. Self-efficacy has been shown to influence motivation, psychological well-being, adherence with treatment regimes and quality of life in multiple sclerosis and other conditions. Objective: To develop a unidimensional scale of MS self-efficacy with robust psychometric properties, suitable for patient self report. Methods: A questionnaire pack covering three MS self-efficacy scales, the Dispositional Resilience Scale and demographic data was posted to MS patients from two MS databases. Data underwent Rasch analysis. Results: Response rate was 309/600 (51.5%). None of the existing MS self-efficacy scales were unidimensional. A new 12-item scale, created by combining items from our two scales, was shown to fit the Rasch model, was unidimensional, and invariant for gender, education and disease duration. Conclusion: The Unidimensional Self-Efficacy scale for MS (USE-MS) provides a simple summated scale for an ordinal estimate of a persons’ self efficacy. A transformation to interval scaling is available for use in the calculation of change scores and effect sizes.