Development and psychometric properties of a joint protection self-efficacy scale

Introduction. Self-efficacy is one of the most powerful determinants of behaviour change. To increase effectiveness of joint protection (JP) education, it may be important to address perceptions of JP self-efficacy directly. The aim of this study was to develop a scale to measure JP self-efficacy (JP-SES) in people with rheumatoid arthritis (RA). Methods. Instrument development included item generation, construct validity, and reliability testing. Rasch analysis was applied to determine construct validity and the revised JP-SES was tested again to confirm validity and establish test--retest reliability and internal consistency. Results. A total of 46 items were generated by literature review, occupational therapists, and people with RA. After semi-structured interviews and field-testing with RA participants, a 26-item questionnaire draft was constructed and tested. Rasch analysis to determine construct validity reduced the JP-SES to 13 items with good overall fit values. Rasch analysis of confirmatory validity resulted in a final 10-item version of the JP-SES. Test--retest results supported the validity of the scale, with high internal consistency (alpha alpha == 0.92) and good test--retest reliability (r(s) == 0.79; p <0.001). Conclusions. The JP-SES is a valid and reliable scale to assess perceived ability of people with RA to apply JP methods. The JP-SES could help stimulate the use of efficacy-enhancing methods in JP education.