Development and validation of a self-efficacy measure for people with multiple sclerosis: the Multiple Sclerosis Self-efficacy Scale.

The aim of this study is to develop and validate a brief measure of self-efficacy specifically for use with people with multiple sclerosis (MS). Self-efficacy is the subjective belief that one can overcome challenges that one is faced with. In order to incorporate the subjective experiences of individuals with MS, a 'patient-focused' methodology has been adopted. Open-ended interviews were used to generate potential scale items. Items were piloted on an initial sample of individuals with MS and reduced to 14 items on the basis of their perceived relevance to this patient group. The final 14-item scale was then used with a further 142 individuals in order to assess its psychometric properties. The scale demonstrated high internal consistency (Cronbach's alpha = 0.81) and test-retest reliability (r = 0.81, P < 0.001) and acceptable validity. Issues concerning the assessment of validity are discussed in terms of the scale's relevancy to individuals with MS and the theoretical issues around the construct of self-efficacy. The scale has shown sensitivity to detect change following a brief therapeutic intervention, with an effect size of 0.502. This MS Self-efficacy Scale could, therefore, be a useful tool in the assessment of psychological adjustment and quality-of-life of individuals with MS.