Mapping utility scores from the Barthel index
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It is not always possible to collect utility-based outcome data, like EQ-5D, needed for conducting economic evaluations in populations of older people. Sometimes, information on other non-utility outcome measures may have been collected. This paper examines the possibility of mapping the EQ-5D from a non-utility-based outcome, the Barthel index.
Data for 1,189 UK intermediate care patients were used. Ordinary least squares (OLS), censored least absolute deviations (CLAD) estimator and multinomial logistic (ML) models were used. The mean absolute error (MAE) and root-mean-squared error (RMSE) were used to estimate the predictive accuracy of eight regression models. Validation of primary models was carried out on random samples of data collected at admission and discharge.
Models where the EQ-5D was entered as a continuous dependent variable and Barthel dimensions used as explanatory variables performed better. CLAD performed best on MAE and OLS on the RMSE, while the ML performed the worst on both measures. The CLAD predicted EQ-5D scores that matched the observed values more closely than the OLS.
It is possible to reasonably predict that the EQ-5D from the Barthel using regression methods and the CLAD model (4) is recommended.
KeywordsMapping Health-related quality of life Older people Utility
We are grateful to colleagues from the Universities of Birmingham and Leicester (the ICNET team) who participated in the National Evaluation of Intermediate Care Services from which data used in this study were obtained. We are also thankful to the intermediate care-coordinators and the staff from the case study sites that provided the quantitative data and clarified follow-up questions. Special thanks go to participants at the UK Health Economists Study Group meeting held at the University of York in July 2006 for comments on an earlier iteration of this work. The National Evaluation was funded by the Department of Health (Policy Research Programme) and the Medical Research Council. The funders were not involved in the study design, in the writing of the manuscript or in the decision to submit the manuscript for publication.
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