A new health status index to measure population health from the EQ-5D VAS score

Presenter: Juan M Cabases, Public University of Navarra

Abstract

Background: For purposes of population health description and comparisons there is no need for preference-based measures elicited using a choice-based method as it is the case for computing QALYs for economic evaluation purposes.
Objectives. We explore the potential use of a health status index based on self-rated EQ-5D VAS score to measure population health and analyze geographical differences, both in health status and also in the valuations that individuals give to the health states, in 7 countries: Finland, Germany, Sweden, United Kingdom, Netherlands, Spain, United States, (N= 12.757), using the database of the EuroQol group.
Methods. Two regression linear models with dummies are developed. Model 1 produces a health status index using the EQ-5D Visual Analogue Sale (VAS score) as dependent variable and the 5 dimensions of EQ-5D as regressors (EQ-VAS index). Model 2 measures country differences in health status and also in the value attached to the health states in each country, in a two-stage procedure: First, the value of self-assessed health status is obtained using the EQ-VAS index as the dependent variable, and dummies to represent the different countries as regressors. Second, to test for differences in the value attached to health states, we used as the dependent variable the difference between the VAS and the EQ-VAS index; the regressors being dummies representing the different countries. In this model the dependent variable, (VAS score – EQ-VAS index), represents the difference between the value that each individual attaches to his or her own health state (VAS score) and the mean value of that health state for the aggregated sample (EQ-VAS index).
Results: There are four possible scenarios combining the 2 variables: the existence or absence of differences in health status and in the valuation of health states between countries. All combinations were found although the most frequent scenarios are two: the combination of country differences in health states valuations but not differences in health status, and country differences in both, health status and health states valuations
Discussion. The health status index developed, EQ-VAS index, is derived directly from the self-perceived VAS and not from hypothetical states. It is meant to be used in population health measures and not for economic evaluation, produces a value set for the 243 EQ-5D health states, is a simple method of valuation and obtainable from routine information of the EQ-5D instrument.
However, the values produced depend crucially on the sample used. Here we used a data base from the EuroQol Group from different countries and periods of time. To make comparisons reliable, we probably need a more homogeneous data set. This would call for a more general inclusion of EQ-5D in population health surveys.

Conclusion. An interesting finding particularly relevant for the design of policy is that different countries give different values to the same health states. This would suggest country-specific values for development of national health policies.