Improving valuation sampling of EQ-5D health states

Adrian Bagust

doi:10.1186/1477-7525-11-14

Abstract

BackgroundThe original valuation exercise which formed the basis of the UK EQ-5D time trade-off social tariff of health states, employed a sampling scheme involving 43 health states. Neither that study, nor other published international valuations studies have used explicit quantifiable criteria to justify the choice of sampled states. New criteria are proposed and methods described to aid researchers in designing improved sampling schemes for future EQ-5D sampling exercises.MethodFour such criteria are described, and applied to assess the merits of four sampling schemes previously reported, using three large observational databases to quantify relative performance. An alternative sampling design conforming to these criteria is described, which aims to generate improved performance.ResultsPrevious published approaches are shown to perform poorly against the measured criteria. The alternative sampling design is demonstrated to provide superior performance on all measures.ConclusionFuture valuation exercises using sampled health states based on this approach may be expected to offer benefits in terms of greater precision, avoidance of bias in favour of less severe states, and a higher proportion of research observations valued directly rather than dependent on extrapolation modelling.

Highlights

The original valuation exercise which formed the basis of the UK EQ-5D time trade-off social tariff of health states, employed a sampling scheme involving 43 health states
In all of the published valuation studies several of the selected health states (12-28%) do not feature at all in the Health Survey for England 1996 (HSE96) population survey [11]. (Table 2) This is to be expected as the more severe health states, which are required for valuing the full range of potential EQ-5D states, will be quite uncommon in the general population
Since the original Measurement and Valuation of Health (MVH) valuation study was published by Dolan [2] in 1997, a great deal of research activity has taken place aimed at extending the global reach of the EQ-5D instrument by local implementation, validation and valuation of the EQ-5D instrument

Summary

Introduction

The original valuation exercise which formed the basis of the UK EQ-5D time trade-off social tariff of health states, employed a sampling scheme involving 43 health states. Nor other published international valuations studies have used explicit quantifiable criteria to justify the choice of sampled states. New criteria are proposed and methods described to aid researchers in designing improved sampling schemes for future EQ-5D sampling exercises. A number of issues were raised concerning the calibration of scores and their reliability as a central element in decision analysis influencing health policy. Particular areas of concern included the reliability of incremental differences in EQ-5D scores, the inclusion of large negative (worse than death) scores in the UK tariff, and the small number of health states directly valued. The basis for sampling health states has been explored further and the findings are reported here

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Results

Discussion

Conclusion