Use of the U.S. and U.K. scoring algorithm for the EuroQol-5D in an economic evaluation of cardiac care

BACKGROUND: Most studies that have used the EuroQol-5D instrument (EQ-5D) have used a scoring algorithm based on preferences solicited from the U.K. population. An algorithm recently was developed for the U.S. population, with studies showing meaningful differences in the results obtained using the 2 algorithms. We recently published an economic evaluation assessing the use of drug-eluting stents in patients undergoing percutaneous coronary intervention (PCI). OBJECTIVES: Using the aforementioned economic evaluation, we describe the EQ-5D utility scores resulting from use of U.S. and U.K. algorithms and explore the differences in the incremental cost-utility ratio (ICER) resulting from use of the different EQ-5D estimates. METHODS: EQ-5D data were obtained from the Alberta Provincial Project for Outcomes Assessment in Coronary Heart (APPROACH) disease registry. Individual responses were scored once with each algorithm. The within-individual difference was calculated (U.S. score - U.K. score). The mean, SD, and range were compared using paired t tests. The resulting ICERs were compared using probabilistic sensitivity analysis. RESULTS: The U.K. mean was statistically different from the U.S. mean (0.83, SD 0.20 vs. 0.87, SD 0.15, P < 0.001). The mean within individual difference was 0.04 with a wide range (-0.02 to +0.41). The resulting ICER are CAN $58,635 (95% confidence interval $198,248g-$34,406) per quality-adjusted life year and CAN $58,229 (95% confidence interval $116,818g-$38,779) per quality-adjusted life year for the U.K. and U.S. algorithms, respectively (P value: 0.07). CONCLUSIONS: The algorithms produce quite notable differences within individuals. The effect on the mean score is less pronounced. In the context of our economic evaluation, however, the impact of using the U.S. algorithm on the ICER is negligible.