What Determines the Shape of an EQ-5D Index Distribution?

31 Pages Posted: 15 Aug 2015

See all articles by David Parkin

David Parkin

Kings College London - Department of Primary Care and Public Health Science

Nancy Devlin

Office of Health Economics

Yan Feng

Office of Health Economics

Date Written: August 1, 2014

Abstract

Background: Distributions of EQ-5D index values in patient and general populations typically have a non-normal distribution, divided into two distinct groups. It is important to understand to what extent this is determined by the way that the EQ-5D index is constructed rather than by the true distribution of ill-health.

Aims: This paper examines the determinants of the ‘two groups’ distribution typical of EQ-5D index data. We examine the extent to which the distribution is attributable to properties of the EQ-5D classification system used to create health state profiles or to the properties of the weights applied to profiles.

Methods: We analyse data from the English NHS PROMs programme (hip and knee replacements and varicose vein and hernia repairs) and from a study of two chronic conditions (asthma and angina). The distributions of EQ-5D index values are compared with distributions from which weights have been stripped, and profile data decomposed into their constituent dimensions and levels. They are also compared with condition-specific indexes and the distributions of EQ-5D indexes using different country weights, both Time Trade-Off and Visual Analogue Scale based.

Results: The EQ-5D picks out differences between patients in respect of dimensions that are mainly observed at level 2 or 3. The weights commonly used to calculate the index exacerbate this grouping by placing a larger weight on level 3 observations, and generate a noticeable gap in index values between the groups.

Conclusions: It is both important and informative to undertake exploratory data analysis on EQ-5D data. The analytical methods used for this may be simple. Concentrating on the EQ-5D index in effect obscures useful information about health states and may even produce misleading information.

Suggested Citation

Parkin, David and Devlin, Nancy and Feng, Yan, What Determines the Shape of an EQ-5D Index Distribution? (August 1, 2014). Available at SSRN: https://ssrn.com/abstract=2630593 or http://dx.doi.org/10.2139/ssrn.2630593

David Parkin (Contact Author)

Kings College London - Department of Primary Care and Public Health Science ( email )

5th Floor Capital House
42 Weston Street
London, SE1 3QD
United Kingdom

Nancy Devlin

Office of Health Economics ( email )

105 Victoria Street
London, SW1E 6QT
United Kingdom
0044 2077478858 (Phone)

Yan Feng

Office of Health Economics ( email )

Southside
105 Victoria Street
London, SW1E 6QT
United Kingdom

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