Background/Purpose

Patient-reported outcomes (PROs) have been recognized as important in evaluating disease status of rheumatoid arthritis (RA). The minimally important difference (MID) in PROs has been studied in RA for physical function, however, the MID for quality of life assessed by European Quality of Life-Five Dimensions (EQ-5D) has not yet been analyzed. Thus, we conducted this study to elucidate MID for EQ-5D. 

Methods   

Participants were patients with RA who enrolled in the IORRA study conducted in October 2011 and April 2012. The IORRA study was established as a large observational cohort of RA patients.in October 2000 and the data collection was conducted biannually. The database includes the EQ-5D, the disease activity score in 28 joints (DAS28), and the Japanese version of the Health Assessment Questionnaire (J-HAQ) for physical disability. Patients self-rated their change in overall status in April 2012 as much better, somewhat better, the same, somewhat worse, or much worse compared to that in October 2011 using a 5-point Likert scale. In this study, the MID for EQ-5D in patients who rated themselves as somewhat better were analyzed. The MID is the means of each patient’s change in the EQ-5D, and the responsiveness to change was evaluated using effect size (ES) which of 0.2 to 0.5 is usually considered as relevant value for the MID.

Results  

A total of 4,847 patients in this study had a mean (standard deviation [SD]) age of 60.4 (13.4) years, disease duration of 14.2 (10.0) years, DAS28 score of 2.9 (1.1), J-HAQ score of 0.64 (0.73), and EQ-5D of 0.800 (0.18), and 85.0% were women. Among them, 745 patients self-rated themselves somewhat better. The mean (SD) change in EQ-5D was 0.018 (0.17) with ES of 0.11 for patients who self-rated themselves somewhat better. When patients rated themselves somewhat better were stratified by baseline DAS28 into groups of remission, low, moderate and high disease activity, the mean (SD) changes in EQ-5D were -0.0002 (0.15), 0.017 (0.15), 0.032 (0.13) and 0.58 (0.12) with ES of 0.001, 0.11, 0.23 and 0.49, respectively. When stratified by baseline J-HAQ into groups of low (J-HAQ<0.5), moderate (0.5≤J-HAQ<1.5) and high (J-HAQ≥1.5) physical disability, the mean (SD) changes in EQ-5D were 0.004 (0.13), 0.027 (0.12) and 0.032 (0.13) with ES of 0.03, 0.21 and 0.24, respectively. When stratified by baseline disease duration into groups of < 2 years, 2-5 years, 5-10 years and ≥10 years, the mean changes (SD) in EQ-5D were 0.043 (0.12), 0.021 (0.16), 0.015 (0.16) and 0.014 (0.16) with ES of 0.33, 0.16, 0.09 and 0.08, respectively. Finally, the MID in EQ-5D in patients with baseline DAS28>3.2, baseline J-HAQ>0.5 and disease duration <5 years was demonstrated as 0.036 with ES of 0.39.

Conclusion

This study demonstrated the MID in EQ-5D in RA patients from the IORRA cohort. The MID in EQ-5D varies in concordance with disease activity, physical disability and disease duration.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/minimally-important-difference-in-the-european-quality-of-life-five-dimensions-in-patients-with-rheumatoid-arthritis/