BACKGROUND: Endorsed by the Outcome MEasures in Rheumatoid Arthritis in Clinical Trials (OMERACT) group, The Effective Consumer Scale (EC-17) was developed in English for patients with musculoskeletal diseases to assess the skills and perceptions important for participating in and managing health care. The objective of this study was culturally to adapt the questionnaire into Swedish and to study its psychometric properties.

METHODS: After translation of the questionnaire into Swedish, two different groups of outpatients from two specialist rheumatology departments participated in the study. Face validity was assessed, together with internal consistency, test-retest and responsiveness of the questionnaire. Construct validity was assessed using the Arthritis Self-Efficacy Scale (ASES), and responsiveness to a five day educational intervention was analysed using the standardized response mean (SRM).

RESULTS: Analyses were based on 124 patients with inflammatory rheumatic diseases, of whom 50 attended the intervention. Data quality met the requirements, with missing values <5%, and floor and ceiling effects <15%. Item total correlations were all >0.4, ranging from 0.49 to 0.88. Cronbach's alpha was 0.93 and 0.95 for the two groups. The test-retest correlation (ICC₂.₁) was 0.94, and there was a significant improvement as a result of the intervention, with an SRM of 0.43. However, the questionnaire had a higher construct validity with the ASES subscale 'other symptoms' than hypothesized a priori (r(s) 0.75).

CONCLUSION: The Swedish version of the EC-17 met the required recommendations for face validity, internal consistency, test-retest reliability and responsiveness. Its construct validity needs to be further established, and the questionnaire needs further testing in different groups of patients and in different interventions. © 2012 John Wiley & Sons, Ltd.