Modelling health state preference data using a non-parametric Bayesian method

This paper reports on the findings from the application of a recently reported approach to modelling health state valuation data. The approach applies a nonparametric model to estimate the revised version of the Health Utilities Index Mark 2 (HUI 2) health state valuation algorithm using Bayesian methods. The data set is the UK HUI 2 valuation study where a sample of 51 states defined by the HUI 2 was valued by a sample of the UK general population using standard gamble. The paper presents the results from applying the nonparametric model and compares these to the original model estimated using a conventional parametric random effects model. The two models are compared in terms of their predictive performance. The paper discusses the implications of these results for future applications of the HUI 2 and further work in this field

Visual Analogue Scales: do they have a role in the measurement of preferences for health states?

Health state preference data are increasingly used to inform national health care resource allocation decisions. In such circumstances it is important to be confident that the data we provide to decision makers is fit for purpose. Whilst there are many unresolved issues in health state preference measurement, there are some areas of agreement on procedures that are inappropriate. The past ten years have seen the publication of a number of papers reporting substantive problems with the use of visual analogue scales to value health states. In this journal Torrance and colleagues reviewed this literature and concluded that Visual Analogue Scales have a limited but useful role in health state preference measurement. In this paper we critically review the arguments advanced by Torrance and colleagues and argue that it is increasingly clear that Visual Analogue Scales are not an appropriate method and that the time has come to accept that VAS should not be used for health state preference measurement

Weighting must wait: incorporating equity concerns into cost effectiveness analysis may take longer than expected

Current practice in economic evaluation is to assign equal social value to a unit of health improvement (“a QALY is a QALY is a QALY”). Alternative views of equity are typically considered separately to efficiency. One proposal seeks to integrate these two sets of societal concerns by attaching equity weights to QALYs. To date, research in pursuit of this goal has focussed on candidate equity criteria and methods for estimating such weights. It has implicitly been assumed that should legitimate, valid, and reliable equity weights become available, it would be a straightforward task to incorporate them into as a separate simple calculation after estimating cost per unweighted QALY. This paper suggests that in many situations these simple approaches to incorporating equity weights will not appropriately reflect the preferences on which the weights are based and therefore equity weights must be incorporated directly into the cost effectiveness analysis. In addition to these technical issues, there are a number of practical challenges that arise from the movement from implicit to explicit consideration of equity. Equity weights should be incorporated in economic evaluation, but not until these challenges have been appropriately addressed

Endothelin and the ischaemic heart

Soon after its identification as a powerful vasoconstrictor peptide, endothelin (ET-1) was implicated as a detrimental agent involved in determining the outcome of myocardial ischaemia and reperfusion. Early experimental studies demonstrated that ETA selective and mixed ETA/ETB receptor antagonists can reduce infarct size and prevent ischaemiainduced ventricular arrhythmias in models of ischaemia/reperfusion, implying that ET-1 acts through the ETA receptor to contribute to injury and arrhythmogenesis. However, as our understanding of the physiology of ET-1 has expanded, the role of ET-1 in the ischaemic heart appears ever more complex. Recent evidence suggests that ET-1 exerts actions on the heart that are not only detrimental (vasoconstriction, inhibition of NO production, activation of inflammatory cells), but which may also contribute to tissue repair, such as inhibition of cardiomyocyte apoptosis. In addition, ET-1-induced mast cell degranulation has been linked to a homeostatic mechanism that controls endogenous ET-1 levels, which may have important implications for the ischaemic heart. Furthermore the mechanism by which ET-1 promotes arrhythmogenesis remains controversial. Some studies imply a direct electrophysiological effect of ET-1, via ETA receptors, to increase monophasic action potential duration (MAPD) and induce early after-depolarisations (EADs), while other studies support the view that coronary constriction resulting in ischaemia is the basis for the generation of arrhythmias. Moreover, ET-1 can induce cardioprotection (precondition) against infarct size and ventricular arrhythmias, through as yet incompletely understood mechanisms. To enable us to identify the most appropriate means of targeting this system in a therapeutically meaningful way we need to continue to explore the physiology of ET-1, both in the normal and the ischaemic heart

Orphan drugs and the NHS: Should we value rarity

Cost effectiveness plays an important part in current decisions about the funding of health technologies. Drugs for rare disease (orphan drugs) are often expensive to produce and, by definition, will benefit only small numbers of patients. Several countries have put measures in place to safeguard research and development of orphan drugs, but few get close to meeting the cost effectiveness criteria for funding by healthcare providers. We examine the justifications for special status for rare diseases and ask whether the cost effectiveness of drugs for rare or very rare diseases should be treated differently from that of other drugs and interventions

Annual league tables of mortality in neonatal intensive care units: longitudinal study. International Neonatal Network and the Scottish Neonatal Consultants and Nurses Collaborative Study Group.[see comment]

OBJECTIVE: To assess whether crude league tables of mortality and league tables of risk adjusted mortality accurately reflect the performance of hospitals. DESIGN: Longitudinal study of mortality occurring in hospital. SETTING: 9 neonatal intensive care units in the United Kingdom. SUBJECTS: 2671 very low birth weight or preterm infants admitted to neonatal intensive care units between 1988 and 1994. MAIN OUTCOME MEASURES: Crude hospital mortality and hospital mortality adjusted using the clinical risk index for babies (CRIB) score. RESULTS: Hospitals had wide and overlapping confidence intervals when ranked by mortality in annual league tables; this made it impossible to discriminate between hospitals reliably. In most years there was no significant difference between hospitals, only random variation. The apparent performance of individual hospitals fluctuated substantially from year to year. CONCLUSIONS: Annual league tables are not reliable indicators of performance or best practice; they do not reflect consistent differences between hospitals. Any action prompted by the annual league tables would have been equally likely to have been beneficial, detrimental, or irrelevant. Mortality should be compared between groups of hospitals using specific criteria-such as differences in the volume of patients, staffing policy, training of staff, or aspects of clinical practice-after adjusting for risk. This will produce more reliable estimates with narrower confidence intervals, and more reliable and rapid conclusions

Disk Evolution in Young Binaries: from Observations to Theory

The formation of a binary system surrounded by disks is the most common outcome of stellar formation. Hence studying and understanding the formation and the evolution of binary systems and associated disks is a cornerstone of star formation science. Moreover, since the components within binary systems are coeval and the sizes of their disks are fixed by the tidal truncation of their companion, binary systems provide an ideal "laboratory" in which to study disk evolution under well defined boundary conditions. In this paper, we review observations of several inner disk diagnostics in multiple systems, including hydrogen emission lines (indicative of ongoing accretion), $K-L$ and $K-N$ color excesses (evidence of warm inner disks), and polarization (indicative of the relative orientations of the disks around each component). We examine to what degree these properties are correlated within binary systems and how this degree of correlation depends on parameters such as separation and binary mass ratio. These findings will be interpreted both in terms of models that treat each disk as an isolated reservoir and those in which the disks are subject to re-supply from some form of circumbinary reservoir, the observational evidence for which we will also critically review. The planet forming potential of multiple star systems is discussed in terms of the relative lifetimes of disks around single stars, binary primaries and binary secondaries. Finally, we summarize several potentially revealing observational problems and future projects that could provide further insight into disk evolution in the coming decadeComment: 16 pages, 7 figures, chapter in Protostars and Planets