Original articlesThe EQ-5D and the Health Utilities Index for permanent sequelae after meningitis: A head-to-head comparison
Introduction
The call for evidence-based medicine requires quantification of health outcomes of diagnostic and therapeutic interventions in (cost-)effectiveness analysis. Health outcomes are commonly defined by two components, i.e., duration of life, and health-related quality of life (or, in short, health status). To take health status into account in effectiveness analysis, composite health outcome measures such as quality adjusted life-years (QALYs) have been developed, combining the outcomes in terms of duration of life and health status using “time” as the common denominator. In QALYs, years lived in an optimal health state count as 1, and years not-lived due to mortality as 0. Years lived with a specified disability are combined with a quality weight, reflecting the relative severity of the disabled health state 1, 2. Despite convergence on the QALY methodology in general, clinical investigators face applicatory choices that may determine the ultimate clinical interpretation of the results. In the present study we address one of the key choices, i.e., that of the health status classification, in the context of a nontrivial clinical problem.
For the emergency department of a pediatric university hospital in The Netherlands we developed a diagnostic prediction rule for bacterial meningitis to minimize the burden and time delay of diagnostic procedures [3]. A cost-utility analysis with QALYs as the general denominator of the wide array of effects was deemed relevant. Even with adequate treatment, bacterial meningitis still carries a mortality risk of 3–4%, while the risk of neurologic sequelae (predominantly hearing impairment, although severe mental retardation, tetraplegia, or localized neurologic disabilities such as paresis or epilepsy also occur) is 9–14% 4, 5, 6. A wrong, delayed, or missed diagnosis of bacterial meningitis increases these risks [7], but the effects are not always unidirectional. It was, therefore, necessary to derive QALY expressions of the distal consequences to make decision-tree analysis and optimization of the diagnostic prediction rule possible.
Currently, two options are available to classify the permanent health status consequences for the purpose of QALY calculations: the EQ-5D, developed by the EuroQol Group, and the Health Utilities Index (HUI), developed at the McMaster University in Hamilton, Canada 8, 9, 10. Both instruments may be regarded as feasible; both are widely used and supported by substantial psychometric evidence. The short EQ-5D patient classification questionnaire (five items) is known to be relatively easy to complete; the HUI patient classification questionnaire with 15 more complicated items has been reported to require slightly more effort (about 5–10 min completion time), but may result into a more comprehensive description of health status. The differences between these two measures preclude their interchangeable application. 11, 12, 13 Intuitively, one can imagine that different quality weights, obtained by two different measures, may well influence results of cost-utility analyses.
We, therefore, conducted an empirical study using clinical data and engaging clinical experts with experience on short- and long-term consequences of bacterial meningitis to decide upon the best classification option. We hypothesized that (1) the EQ-5D classification would be superior from a practical point of view but that (2) the HUI classification would be more precise and more discriminative, and that (3) the EQ-5D and HUI would produce roughly the same quality weights.
Section snippets
General approach
We defined eight sequelae (including “healthy”) based on literature reports 4, 5, 6, which represented the possible outcomes of the decision tree underlying the diagnostic prediction rule. A nontechnical narrative description of the permanent health state was constructed for each separate sequel. These descriptions of the sequelae (“stimuli”) were presented to clinical experts, who then independently classified each sequel using the two available classification schemes (EQ-5D and HUI)
Results
Twenty-eight pediatricians completed the classification task: 16 male and 12 female, with a mean age of 45.8 years (SD = 6.5). They had an average of 13.8 year (SD = 6.4) of practical experience.
Discussion
In this study we compared three measures (EQ-5D and two versions of the Health Utilities Index) for the classification and valuation of health states, mainly in the light of the quality weights they generated for the seven case descriptions, but also as regards such aspects as the feasibility and reliability of the classification. Such an empirical head-to-head comparison may help in deciding on which measure should be the instrument of choice in particular disease contexts. Furthermore, this
Acknowledgements
We would like to extend our grateful thanks to L.E. Borst, MD PhD, A. van Linge, MD PhD, E. Weijers, MD, and C.E. Catsman, MD PhD, for their cooperation in developing the case descriptions. We also indebted to the general pediatricians from the ‘Section Academic General Pediatricians’ of the Dutch Pediatric Association for classifying the case descriptions. In addition, we offer our gratitude to I. Hiemstra, MD, and G. Derksen-Lubsen, MD PhD, for their general support and advice, and G.J.J.M.
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