Evidence of preference construction in a comparison of variants of the standard gamble method

An increasingly important debate has emerged around the extent to which techniques such as the standard gamble, which is used, amongst other things, to value health states, actually serve to construct respondents' preferences rather than simply elicit them. According to standard theory, the variant used should have no bearing on the numbers elicited from respondents, i.e. procedural invariance should hold. This study addresses this debate by comparing two variants of standard gamble in the valuation of health states. It is a mixed methods study that combines a quantitative comparison with the probing of respondents in order to ascertain possible reasons for the differences that emerged. Significant differences were found between variants and, furthermore, there was evidence of an ordering effect. Respondents' responses to probing suggested that they were influenced by the method of elicitation

Does the National Institute for Health and Clinical Excellence take account of factors such as uncertainty and equity as well as incremental cost-effectiveness in commissioning health care services? A binary choice experiment

Background: NICE is an independent organisation responsible for providing national guidance on the promotion of good health and the prevention and treatment of ill health in England and Wales. One of NICE’s main roles is to produce national guidance on the use of health technologies within the NHS. Despite the Institute’s recent efforts to clarify the way in which its Appraisal Committees reach their recommendations concerning the use of health technologies, there remains ambiguity about how cost-effectiveness evidence is interpreted alongside other considerations such as the degree of clinical need within the patient population, and the degree of uncertainty surrounding cost-effectiveness estimates. Objective: To explore whether the NICE takes account of factors such as uncertainty and equity as well as incremental cost-effectiveness in commissioning health care services. Methods: A binary choice experiment was undertaken using NICE’s three Appraisal Committees. The experiment included five attributes: (1) Incremental cost-effectiveness (2) Degree of economic uncertainty (3) Age of the target population (4) Baseline health-related quality of life (5) Availability of other therapies A choice questionnaire detailing 18 scenarios was administered to NICE’s Appraisal Committees. For each scenario, respondents were asked to indicate whether they would recommend the intervention under consideration or not. The stated preference data obtained from respondents were analysed using a random effects logit regression model. Results: A response rate of 46% was obtained from the Appraisal Committees. The regression model suggests that increases in cost-effectiveness, economic uncertainty, and the availability of other therapies are associated with statistically significant reductions in the odds of adoption (p<0.05). The transition from a very low to a comparatively high level of health-related quality of life is also associated with a statistically significant reduction in the odds of a positive recommendation. Smaller changes in health-related quality of life, and the age of the target population are not associated with a statistically significant reduction in the odds of a positive recommendation. Analysis of revealed preference data indicates that the model is capable of distinguishing between those technologies which the Appraisal Committees would be highly likely to recommend, and those technologies which appear to be less attractive, although further external validation is warranted. Conclusion: The modelling suggests that cost-effectiveness, uncertainty and certain equity concerns influence the NICE Appraisal Committees’ recommendations on the use of health technologies. The modelling results appear to support Rawlins and Culyer’s notion of a probabilistic cost-effectiveness threshold approach; the "mythical" £30,000 per QALY gained threshold assumed within the literature is not supported by this stated preference modelling analysis

Does the National Institute for Health and Clinical Excellence take account of factors such as uncertainty and equity as well as incremental cost-effectiveness in commissioning health care services? A binary choice experiment

Background NICE is an independent organisation responsible for providing national guidance on the promotion of good health and the prevention and treatment of ill health in England and Wales. One of NICE’s main roles is to produce national guidance on the use of health technologies within the NHS. Despite the Institute’s recent efforts to clarify the way in which its Appraisal Committees reach their recommendations concerning the use of health technologies, there remains ambiguity about how cost-effectiveness evidence is interpreted alongside other considerations such as the degree of clinical need within the patient population, and the degree of uncertainty surrounding cost-effectiveness estimates. Objective To explore whether the NICE takes account of factors such as uncertainty and equity as well as incremental cost-effectiveness in commissioning health care services. Methods A binary choice experiment was undertaken using NICE’s three Appraisal Committees. The experiment included five attributes: (1) Incremental cost-effectiveness (2) Degree of economic uncertainty (3) Age of the target population (4) Baseline health-related quality of life (5) Availability of other therapies A choice questionnaire detailing 18 scenarios was administered to NICE’s Appraisal Committees. For each scenario, respondents were asked to indicate whether they would recommend the intervention under consideration or not. The stated preference data obtained from respondents were analysed using a random effects logit regression model. Results A response rate of 46% was obtained from the Appraisal Committees. The regression model suggests that increases in cost-effectiveness, economic uncertainty, and the availability of other therapies are associated with statistically significant reductions in the odds of adoption (puncertainty; equity; cost-effectiveness; public health

Investigations on entropy layer along hypersonic hyperboloids using a defect boundary layer

A defect approach coupled with matched asymptotic expansions is used to derive a new set of boundary layer equations. This method ensures a smooth matching of the boundary layer with the inviscid solution. These equations are solved to calculate boundary layers over hypersonic blunt bodies involving the entropy gradient effect. Systematic comparisons are made for both axisymmetric and plane flows in several cases with different Mach and Reynolds numbers. After a brief survey of the entropy layer characteristics, the defect boundary layer results are compared with standard boundary layer and full Navier-Stokes solutions. The entropy gradient effects are found to be more important in the axisymmetric case than in the plane one. The wall temperature has a great influence on the results through the displacement effect. Good predictions can be obtained with the defect approach over a cold wall in the nose region, with a first order solution. However, the defect approach gives less accurate results far from the nose on axisymmetric bodies because of the thinning of the entropy layer

Evolution of the SPS Power Converter Controls towards the LHC Era

By the end of the nineties, the power converter control system (Mugef) of the CERN proton accelerator (SPS) had undergone a complete modernization. This resulted in newly developed hardware for function generation, measurement and I/O in a VME environment, under the LynxOS real-time operating system. This has provided a platform on which extensions can be developed for future operation in the Large Hadron Collider (LHC) era. This paper describes some of these extensions, in particular a fast Surveillance and Interlock system for monitoring the power converter output currents. This will be mandatory for the safe operation of the SPS transfer lines TI2 & TI8 to LHC and for similar applications in the future. The strategies employed to cope with various failure modes of the power converters and the timely activation of the interlock are outlined. The new SPS controls infrastructure now under development, will give rise to new modes of operation for the Mugef systems. Integration with the proposed middleware must be undertaken in a structured evolution, while retaining compatibility with the current usage.Comment: Paper is 3 pages for ICAPEPCS 01 27 - 30 November 2001 San Jose. John C L Brazier is the principal author and a consultant to CERN (hence the CERN Email address but UK Organisation

A review of generic preference-based measures of health-related quality of life in visual disorders

Purpose: This review examines generic preference based measures and their ability to reflect health related quality of life in patients with visual disorders. Methods: A systematic search was undertaken to identify clinical studies of patients with visual disorders where health state utility values (HSUVs) were measured and reported. Data were extracted to assess the validity and responsiveness of the measures. A narrative synthesis of the data was undertaken due to the heterogeneity between different studies. Results: There was considerable heterogeneity in the 31 studies identified in terms of patient characteristics, visual disorders and outcomes reported. Vision loss was associated with a reduction in scores across the preference-based measure, but the evidence on validity and responsiveness was mixed. The EQ-5D’s performance differed according to condition, with poor performance in age-related macular degeneration and diabetic retinopathy. The more limited evidence on the HUI-3 found it performed best in differentiating between severity groups of patients with glaucoma, AMD, cataracts and diabetic retinopathy. One study reported data on the SF-6D and showed it was able to differentiate between patients with AMD. Conclusion: The performance of the EQ-5D in visual disorders was mixed. The HUI-3 seemed to perform better in some conditions, but the evidence on this and SF-6D is limited. More head to head comparisons of these three measures are required. The new 5-level version of EQ-5D may do better at the milder end of visual function and there is research being undertaken into adding a vision relevant dimension

Using Rasch analysis to form plausible health states amenable to valuation: the development of CORE-6D from CORE-OM in order to elicit preferences for common mental health problems

Purpose: To describe a new approach for deriving a preference-based index from a condition specific measure that uses Rasch analysis to develop health states. Methods: CORE-OM is a 34-item instrument monitoring clinical outcomes of people with common mental health problems. CORE-OM is characterised by high correlation across its domains. Rasch analysis was used to reduce the number of items and response levels in order to produce a set of unidimensionally-behaving items, and to generate a credible set of health states corresponding to different levels of symptom severity using the Rasch item threshold map. Results: The proposed methodology resulted in the development of CORE-6D, a 2-dimensional health state description system consisting of a unidimensionally-behaving 5-item emotional component and a physical symptom item. Inspection of the Rasch item threshold map of the emotional component helped identify a set of 11 plausible health states, which, combined with the physical symptom item levels, will be used for the valuation of the instrument, resulting in the development of a preference-based index. Conclusions: This is a useful new approach to develop preference-based measures where the domains of a measure are characterised by high correlation. The CORE-6D preference-based index will enable calculation of Quality Adjusted Life Years in people with common mental health problems

Estimating population cardinal health state valuation models from individual ordinal (rank) health state preference data

Ranking exercises have routinely been used as warm-up exercises within health state valuation surveys. Very little use has been made of the information obtained in this process. Instead, research has focussed upon the analysis of health state valuation data obtained using the visual analogue scale, standard gamble and time trade off methods. Thurstone’s law of comparative judgement postulates a stable relationship between ordinal and cardinal preferences, based upon the information provided by pairwise choices. McFadden proposed that this relationship could be modelled by estimating conditional logistic regression models where alternatives had been ranked. In this paper we report the estimation of such models for the Health Utilities Index Mark 2 and the SF-6D. The results are compared to the conventional regression models estimated from standard gamble data, and to the observed mean standard gamble health state valuations. For both the HUI2 and the SF-6D, the models estimated using rank data are broadly comparable to the models estimated on standard gamble data and the predictive performance of these models is close to that of the standard gamble models. Our research indicates that rank data has the potential to provide useful insights into community health state preferences. However, important questions remain

Proceed with caution: an economic perspective on the UK's value based pricing proposals

The shift from the Pharmaceutical Pricing Regulation Scheme to Value Based Pricing (VBP) is an important change in the way that medicines will be priced, and consequently, reimbursed in the United Kingdom. Whilst the opportunity to purchase new medicines based on value to society is one that should be welcomed, we should proceed with caution. We highlight ten issues that should be considered relating to innovation, the role and meaning of funding threshold and the adjustments to reflect burden of illness, therapeutic innovation and improvement and wider societal factors. Most importantly, the assessment of value should continue to be based on the characteristics of the displaced activities (e.g. the health produced). To a large extent, all that is changing under VBP are the characteristics being considered; weighted health rather than unweighted health. In addition, we should not totally abandon a cost-utility framework for appraisal just because its current formulation does not match the wider perspective now desired by government