Background: The purpose of this study was to evaluate the impact of using different country-specific value sets in EQ-5D-5L based outcome analyses.
Methods: We obtained data on patients surgically treated with total hip arthroplasty (THA) between 2017 and 2019 from the national Swedish Hip Arthroplasty Register. Preoperative and one-year postoperative data on a total of 28,902 procedures were available for analysis. The EQ-5D-5L health states were coded to the EQ-5D-5L preference indices using 13 European value sets. The EQ-5D-5L index distributions were then estimated with kernel density estimation. The change in EQ-5D-5L index before and one year after treatment was evaluated with the standardized response mean (SRM). The lifetime gain in quality-adjusted life years (QALYs) was estimated with a 3.5% annual QALY discount rate.
Findings: There was a marked variability in means and shapes of the resulting EQ-5D-5L index distributions. There were also considerable differences in the EQ-5D-5L index distribution shape before and after the treatment using the same value set. The effect sizes of one-year change (SRM) were similar for all value sets. However, the differences in estimated QALY gains were substantial.
Interpretation: The EQ-5D-5L index distributions varied considerably when a single large data set was applied to different European EQ-5D-5L value sets. The most pronounced differences were between the value sets based on experience-based valuation and the value sets based on hypothetical valuation. This illustrates that experience-based and hypothetical value sets are inherently different and also that QALY gains derived with different value sets are not comparable. Our findings are of importance in study planning since the results and conclusions of a study depend on the choice of value set.
Funding: None.