Is there a case for using Visual Analogue Scale valuations in Cost-Utility Analysis?

This paper critically reviews theoretical and empirical propositions regarding visual analogue scale (VAS) valuations of health states and their use in Cost Utility Analysis. An oft-repeated conclusion in the economic evaluation literature is the inferiority, on theoretical grounds, of VAS valuations. Common criticisms are that VAS lacks a theoretical foundation; that VAS values are not ‘choice based’; that VAS values are not consistent with utility-under-uncertainty requirements; and that context and range effects observed in VAS valuation data mean that they cannot even be considered to represent measurable value functions. We address each of the above points, critically reviewing the economic and psychometric literature relating to theories of utility and theories of utility measurement, and the welfarist and non-welfarist literature relating to social choices and QALYs. We conclude that there are strong grounds, both theoretical and empirical, for challenging the apparently emerging consensus that VAS valuations should not be used in economic assessments. The theoretical appeal of alternatives such as the standard gamble is valid only at the level of individuals, rather than social decision-making. Further, the non-welfarist foundations of CUA do not require health state valuations to be grounded in any particular theory of utility, suggesting that the selection of the appropriate valuation method should be based on empirical performance. The VAS has important advantages over rival techniques such as standard gamble and time trade-off. However, we identify a number of areas in which further research is required to establish and consolidate the potential of VAS as a valuation method

Statistical analysis of EQ-5D profiles: does the use of value sets bias inference?

Health state profile data, such as those provided by the EQ-5D, are widely collected in clinical trials, population surveys and a growing range of other important health sector applications. However, these profile data are difficult to summarise to give an overall view of the health of a given population that can be analysed for differences between groups or within groups over time. A common way of short-cutting this problem is to transform profiles into a single number, or index, using sets of weights, often elicited from the general public in the form of values. Are there any problems with this procedure? In this paper we demonstrate the underlying effects of the use of value sets as a means of weighting profile data. We show that any set of weights introduces an exogenous source of variance to health profile data. These can distort findings about the significance of changes in health between groups or over time. No set of weights is neutral its effect. If a summary of patient reported outcomes is required, it may be better to use an instrument that yields this directly – such as the EQ VAS – along with the descriptive instrument. If this is not possible, researchers should have a clear rationale for their choice of weights; and be aware that those weighs may exert a non-trivial effect on their analysis. This paper focuses on the EQ-5D, but the arguments and their implications for statistical analysis are relevant to all health state descriptive systems

Using the EQ-5D as a performance measurement tool in the NHS

In a landmark move, the UK Department of Health (DH) is introducing the routine use of Patient Reported Outcome Measures (PROMs) as a means of measuring the performance of health care providers in improving patient health. From April 2009 all patients will be asked to complete both generic (EQ-5D) and condition specific PROMs before and after surgery for four elective procedures; the intention is to extend this to a wide range of other NHS services. The aim of this paper is to report analysis of the EQ-5D data generated from a pilot study commissioned by the DH, and to consider the implications of the results for their use as performance indicators and measures of patient benefit. The EQ-5D has the potential advantage in the context of PROMs of enabling comparisons of performance across services as well as between providers; and in facilitating assessments of the cost effectiveness of NHS services. We present two new methods we have developed for analysing and displaying EQ-5D profile data: a Paretian Classification of Health Change, and a Health Profile Grid. Using these methods, we show that EQ-5D data can readily be used to generate useful insights into differences between providers in improving overall changes in health; results are also suggestive of striking differences in changes in health between surgical procedures. We conclude by noting a number of issues that remain to be addressed in the use of PROMs data as a basis for performance indicators

Halide doping effects on transparent conducting oxides formed by aerosol assisted chemical vapour deposition

We report on the effect of halide doping on the Aerosol-assisted Chemical Vapour Deposition of tin oxide. Specifically, the importance of precursor interactions is highlighted. A halide exchange reaction involving part substitution of the tin precursor is believed to occur in the solvent; the complex acting as a marker for improved films with improved transparent-conducting properties. Precursor mixtures of butyltin trichloride and potassium halide (X = F, Cl, Br, I) in propan-2-ol were deposited at a substrate temperature of 450 °C using air carrier gas. Hall Effect results indicate that fluorine gave the best performing n-type transparent conducting thin films that exhibited high optical transparency (> 80% at 550 nm) and resistivity values of 4.9 × 10− 4 Ω.cm, with charge carrier density and carrier mobility values of 8.85 × 1020 cm− 3 and 15 cm3/V.s respectively. Such parameters yield high figures of merit

Transport and Magnetic Properties of FexVse2 (x = 0 - 0.33)

We present our results of the effect of Fe intercalation on the structural, transport and magnetic properties of 1T-VSe2. Intercalation of iron, suppresses the 110K charge density wave (CDW) transition of the 1T-VSe2. For the higher concentration of iron, formation of a new kind of first order transition at 160K takes place, which go on stronger for the 33% Fe intercalation. Thermopower of the FexVSe2 compounds (x = 0 - 0.33), however do not show any anomaly around the transition. The intercalation of Fe does not trigger any magnetism in the weak paramagnetic 1T-VSe2, and Fe is the low spin state of Fe3+.Comment: 7 pages, 8 figures, 2 table

A novel approach for quality control system using sensor fusion of infrared and visual image processing for laser sealing of food containers

This paper presents a new mechatronic approach of using infrared thermography combined with image processing for the quality control of a laser sealing process for food containers. The suggested approach uses an on-line infrared system to assess the heat distribution within the container seal in order to guarantee the integrity of the process. Visual image processing is then used for quality assurance to guarantee optimum sealing. The results described in this paper show examples of the capability of the condition monitoring system to detect faults in the sealing process. The results found indicate that the suggested approach could form an effective quality control and assurance system

Forces from highly focused laser beams: modeling, measurement and application to refractive index measurements

The optical forces in optical tweezers can be robustly modeled over a broad range of parameters using generalsed Lorenz-Mie theory. We describe the procedure, and show how the combination of experimental measurement of properties of the trap coupled with computational modeling, can allow unknown parameters of the particle - in this case, the refractive index - to be determined.Comment: 5 pages, 4 figures, presented at 17th AIP Congress, Brisbane, 200