Utilities of the EQ-5D: Transferable or Not?

Presenter: Saskia Knies, Maastricht University

Abstract

BACKGROUND: It is assumed that costs always differ between jurisdictions and should therefore be adjusted to the decision country. Nevertheless, the clinical effectiveness of health care interventions may be transferable, but the transferability of population preferences remains unclear. A frequently used generic instrument to measure health-related quality of life in economic evaluations is the EQ-5D, which has been developed to compare preferences across countries. At the moment, the EQ-5D has several national value sets. However, it has become standard practice to directly adopt utilities from studies instead of using the own national value set. It is not clear if this practice is advisable, because of dissimilarities between the value sets.

OBJECTIVE: To examine the effects of differences between national EQ-5D value sets on absolute and incremental utilities of health states. Next to that, to examine what degree differences can be explained by methodological factors.

METHODS: First, the relative importance of level two and level three for all domains was compared by ranking the coefficients across the value sets. Second, two hypothetical health states (21232 and 33321) were selected for additional analysis by comparing the utilities as scored by the value sets. Next to that, the incremental influence of one or two deteriorations of the health states on the utility score were determined. Third, differences between the value sets were examined more detailed by using multilevel analysis to investigate the role of methodological differences between the valuation studies.

RESULTS: Differences can be perceived in the population preferences for the domains between the national value sets of the EQ-5D. The value of the utilities of the two health states show that the value sets differ substantially. Furthermore, the differences between the increments of the deteriorations are large. The results of the multilevel analysis indicated that the differences can partly be explained by the type of valuation method. Other methodological factors also have some influence.

DISCUSSION: All results indicate that the differences between the EQ-5D value sets are considerable and should not be ignored. Therefore, the standard practice of blindly transferring utilities across jurisdictions without any adjustment is not advisable. However, the differences between the value sets can largely be explained by methodological differences in the valuation studies. The remaining differences may reflect cultural dissimilarities between countries. Therefore further research should focus on investigating the most valid method for determining new value sets to calculate utilities for health states. Next to that, more research is needed on the transferability of population preferences across jurisdictions.