Face validity and reliability test of the Danish version of the compliance questionnaire rheumatology in patients with early rheumatoid arthritis.

Background: Supporting adherence to medication is an essential part of the treatment and care of patients with rheumatic and musculoskeletal diseases. The Compliance Questionnaire Rheumatology (CQR) measures adherence in rheumatic diseases through 19 items covering drug-taking behaviour to identify the reasons for adhering to treatment and the factors that contribute to suboptimal adherence. The objective of this study was to present the translation of the CQR into Danish and the face validity and reliability test.

Methods: The CQR was translated into Danish according to international guidelines, followed by a face validity test among 10 patients with rheumatoid arthritis in 2009. The test-retest reliability of the Danish CQR was evaluated in 49 patients with rheumatoid arthritis in 2020 - 2021 using the standard error of the measurement (SEM) converted into the minimally detectable change (MDC) and the intraclass correlation coefficient (ICC). Questionnaires were administered with a minimum of 10 days between assessments.

Results: The participants in the reliability test had a mean age of 57.4 years (SD 16.1) and a mean disease duration of 1.13 years (range 2 months-2 years). The mean CQR score in the test and retest was 62.7 (confidence interval (CI) 58.8; 66.6) and 62.5 (CI 58.9; 66.1), respectively, with a SEM of 8.59 (7.16; 10.73) and an MDC of 16.83. A satisfactory test-retest reliability was confirmed by an ICC value of 0.79 (CI 0.68; 0.89).

Conclusion: The Danish CQR has satisfactory test-retest reliability in patients newly diagnosed with rheumatoid arthritis and is considered a reliable tool to measure adherence in this group.