Assessing utility values in rheumatoid arthritis: A comparison between time trade‐off and the EuroQol

Objective

To compare the utility values and quality‐adjusted life years (QALYs) obtained by the Time Trade‐Off instrument (TTO) and the EuroQol‐5D (EQ‐5D) in patients with rheumatoid arthritis (RA); to analyze the association between utility values and Disease Activity Score 28 (DAS28) and Health Assessment Questionnaire (HAQ).

Methods

We conducted a longitudinal, prospective, 1‐year study of RA patients selected randomly from 10 rheumatology clinics. TTO and EQ‐5D were administered at 4 scheduled visits.

Results

The study sample comprised 300 RA patients (82% women, mean age 59 years, mean disease duration 10.3 years). A total of 260 patients completed both the TTO and the EQ‐5D at baseline, and the mean ± SD TTO scores were significantly higher than the EQ‐5D scores (0.81 ± 0.22 versus 0.53 ± 0.35, P < 0.0001). The intraclass correlation coefficient (ICC) for the utility methods was 0.19. Data about changes in both TTO and EQ‐5D scores during the study year were available in 163 patients. These changes tended to be larger in the TTO scores than the EQ‐5D scores (mean ± SD 0.05 ± 0.25 versus ?0.005 ± 0.35, P = 0.054). The ICC for the mean changes in the utility scores was 0.24. Patients obtained a mean ± SD of 0.04 ± 0.20 QALYs based on TTO scores and 0.004 ± 0.27 based on EQ‐5D scores (P = 0.12). At baseline, the EQ‐5D scores were highly correlated with the HAQ (r = ?0.74) and moderately correlated with the DAS28 (r = ?0.47), whereas the TTO correlated poorly with both the HAQ and DAS28. Correlation between the mean change in the EQ‐5D and in the HAQ was moderate (r = ?0.55).

Conclusion

TTO and EQ‐5D do not yield the same utility values. The results suggest that the EQ‐5D is more representative of RA status than the TTO, a valuable conclusion when addressing economic evaluations in RA.