Pos0720 measuring functional disability in giant cell arteritis: the validity, reliability and responsiveness of the gca-disability index (gca-di)

Background Giant cell arteritis (GCA) is the most frequent systemic vasculitis, typically affecting patients over 50. The disease burden includes a chronic course and a subsequent prolonged treatment, especially because of a high risk of relapse that affects approximately half of patients. Taken together, the disease and its symptoms, the chronic course and the treatment probably have an impact on the patients’ functional ability as well as quality of life. Though functional disability has been identified as a core outcome measure in GCA, few studies have been dedicated to assess for the patients for this core measure. Objectives To test the GCA-disability index (GCA-DI) questionnaire for validity, reliability and responsiveness in patients with Giant Cell Arteritis. Methods The psychometric properties of GCA-DI were tested in 57 patients with GCA, mean age 63.6 (+/- 5.4), 77.2% women, mean disease duration 2.1 weeks (+/- 3.1 days). At baseline, all the patients completed the GCA-DI, and the Health Assessment Questionnaire (HAQ). The patients were then asked to return to the clinic after having their blood tests and X-rays done to complete another copy of the questionnaire. Also, all the patients were asked to complete another copy of the questionnaire in their follow up visit in 4-weeks’ time. This facilitated the assessment for validity, reliability and responsiveness. In addition, all the patients were asked to complete a copy of multidimensional Patient Reported Outcomes for GCA. Patient global assessment for functional disability was also recorded (0-100 VAS). Of the 57 patients who completed the health status instruments on two occasions, 53 were included in the responsiveness analyses. The test-retest reliability of the GCA-DI questionnaire was calculated using intraclass correlation coefficients (ICCs). Criterion validity was assessed using Spearman’s correlations, while responsiveness was evaluated by 3 different methods: (1) effect size (the mean difference between the baseline scores and the follow-up scores divided by the standard deviation of the baseline scores); (2) standardized response mean (the mean change in scores divided by the standard deviation of the change in scores). Results GCA-DI fulfilled the established criteria for validity, reliability and responsiveness. Significant correlations were seen between GCA-DI scores and HAQ scores (rho = 0.672), Patient Global Assessment functional disability (rho = 0.629), pain (rho = 0.633), Test-retest reliability was satisfactory, with ICCs of 0.935. The results of responsiveness analysis indicated that the GCA-DI was sensitive to change. Standardized effect size was 2.84 after 4-weeks. Conclusion Our data suggest that the GCA-disability index can be considered as a reliable, valid and responsive tool for measuring physical functioning in GCA patients. It is suitable for use in clinical trials and daily clinical practice. Its generalizability and utility for assessing treatment and functional outcomes should be evaluated in larger settings. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests None Declared.