Objective: To test the hypothesis that the Health Utilities Index Mark III (HUI3) and the SF-6D, based on the SF-36, generate similar health state values, and to test and compare their discriminant validity and responsiveness.
Methods: The HUI3 and SF-36 were administered to 331 patients enrolled in a double-blind, multinational phase III clinical trial in patients undergoing percutaneous coronary intervention before hospital discharge and 6 months thereafter.
Results: The mean SF-6D baseline health state score was 0.67 compared to the HUI3 of 0.63 with r of 0.616 and intraclass correlation coefficient of 0.40. The relationship was nonlinear with greatest divergence found at the lower levels of health. Both measures were found to agree with known differences in health and to be responsive to changes over time. Nevertheless, disagreement resulted in different estimates of change from baseline (0.08 vs. 0.154).
Conclusion: Both measures deployed in the present study were found to have discriminant validity, and to be responsive to changes over time in coronary artery disease conditions. Nevertheless, the measures generated different estimates of health state values for this patient population. These differences might in part be the consequence of the health status descriptive system for the HUI that may have been more in line with the hospitalized state than that for the SF-6D. These findings seemed to indicate that measures deployed are not interchangeable for use in cost-utility analysis. More head-to-head comparisons between these two measures are needed to further define and compare relationships in different patient populations.