Translation to Brazilian Portuguese, cultural adaptation and psychometric properties of 8-item Arthritis Self-Efficacy Scale (ASES-8)

BACKGROUND: Self-efficacy refers to one's belief in one's ability to organize, perform actions and face challenges in order to achieve goals and motivation. High self-efficacy improves disease coping and adherence to treatment among patients with rheumatoid arthritis. The objective of this study was to translate, culturally adapt and test the reproducibility of the 8-item Arthritis Self-Efficacy Scale (ASES-8) questionnaire for use in Brazil. DESIGN AND SETTING: Validation study conducted in university outpatient clinics. METHODS: The questionnaire was translated into Brazilian Portuguese and then back-translated into English. The final version in Portuguese was tested on 30 patients with rheumatoid arthritis and was shown to be understandable and culturally adapted. A further 32 patients with rheumatoid arthritis were evaluated three times using the questionnaire. On the first occasion, two evaluators applied the questionnaire to check inter-evaluator reproducibility. After 15 days, one of the evaluators reassessed the patients to verify intra-evaluator reproducibility. At the first assessment, to test the construct validity of ASES-8, the Numerical Pain Scale, Health Assessment Questionnaire, Beck Depression Inventory and Short Form-36 questionnaire were also applied to all the patients. RESULTS: The inter and intra-evaluator correlation coefficients for ASES-8 were high. Cronbach's alpha was higher than 0.90 for the questionnaire, indicating excellent internal consistency. There were moderate correlations between ASES-8 and most of the instruments tested, indicating good construct validity. CONCLUSION: ASES-8 was translated and adapted to the Portuguese language for Brazil. This instrument is valid, reproducible and reliable for evaluating self-efficacy among patients with rheumatoid arthritis.