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Abstract
Objective
Assessment of health-related quality of life in patients with rheumatoid arthritis (RA) has become important in health research. Health economists have used linear regression equations to mathematically transform changes in HAQ scores into EQ5D data, which can be used to calculate quality adjusted life years (QALYs). We aimed to examine whether a given approach is justified.
Methods
A total of 223 patients with RA were recruited from the Hospital for Rheumatic Diseases at Hanyang University. They completed the HAQ and EQ5D and a correlation analysis was performed between the two instruments. We compared HAQ and EQ5D score changes for patients who completed the EQ5D and HAQ at first and second visits (n=159). Predicted EQ5D was estimated from the HAQ using the calculating method of Bansnack et al. The mean difference between the predicted EQ5D from the HAQ and observed health utility score at the first visit and change during the study were tested by the paired t-test.
Results
In the cross-sectional study, EQ5D scores were moderately inversely correlated with HAQ (r=–0.716, p < 0.001). However, the predicted EQ5D from the HAQ was significantly different from the observed EQ5D (p=0.001; 95% confidence interval [CI] 0.020~0.079). The change in EQ5D was also inversely correlated with the change in the HAQ (r=–0.615, p < 0.001), and change in the predicted EQ5D scores corresponded well with changes in observed health utility scores (p=0.155; 95% CI (–0.0873~0.0140).
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Fig. 1.
Cross-sectional observational study. (A) EQ5D scores were moderately inversely correlated with HAQ (r=.0.716, p0.001), (B) Distribution of HAQ, (C) Distribution of EQ5D.
Fig. 2.
Longitudinal observational study. (A) Change in EQ5D was moderately inversely correlated with HAQ change (r=.0.615, p0.001), (B) Distribution of changes in HAQ, (C) Distribution of changes in EQ5D.
Table 1.
Sociodemographic and clinical features in patients with rheumatoid arthritis
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