Tails from the Peak District: Adjusted Censored Mixture Models of EQ-5D Health State Utility Values

Health state utility data generated using the EQ-5D instrument are typically right bounded at one with a substantial gap to the next set of observations, left bounded by some negative value, and are multi modal. These features present challenges to the estimation of the e¤ect of clinical and socioeconomic characteristics on health utilities. We present an adjusted censored model and then use this in a ‡exible, mixture modelling framework to address these issues. We demonstrate superior performance of this model compared to linear regression and Tobit censored regression using a dataset from repeated observations of patients with rheumatoid arthritis. We …nd that three latent classes are appropriate in estimating EQ-5D from function, pain and sociodemographic factors. Analysis of utility data should apply methods that recognise the distributional features of the data. KEYWORDS:Mixture models, Latent Class model, Censored regression, EQ-5D, Mapping JEL CLASSIFICATION: I10, C34, C13,C16 ADDRESS FOR CORRESPONDENCE: Mónica Hernández Alava. Health Economics and Decision Science, School of Health and Related Research, University of She¢ eld, Regent Court, 30 Regent Street, She¢ eld S1 4DA. Email: monica.hernandez@she¢ eld.ac.uk * We are grateful to Ernest Choy and David Scott for providing access to the CARDERA trial data and to Steve Pudney and Simon Dixon for helpful comments on previous drafts. Funding was provided by the NIHR Research for Patient Bene…t scheme. All responsibility for the analysis and interpretation of the data presented here lies with the authors.