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

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

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

GOES-I/M ascent maneuvers from transfer orbit to station

The Geostationary Operational Environmental Satellite (GOES)-I/M station acquisition sequence consists nominally of three in-plane/out-of-plane maneuvers at apogee on the line of relative nodes and a small in-plane maneuver at perigee. Existing software to determine maneuver attitude, ignition time, and burn duration required modification to optimize the out-of-plane parts and admit the noninertial, three-axis stabilized attitude. The Modified Multiple Impulse Station Acquisition Maneuver Planning Program (SENARIO2) was developed from its predecessor, SCENARIO, to optimize the out-of-plane components of the impulsive delta-V vectors. Additional new features include commputation of short term J sub 2 perturbations and output of all premaneuver and postmaneuver orbit elements, coarse maneuver attitudes, propellant usage, spacecraft antenna aspect angles, and ground station coverage. The output data are intended to be used in the launch window computation and by the maneuver targeting computation (General Maneuver (GMAN) Program) software. The maneuver targeting computation in GMAN was modified to admit the GOES-I/M maneuver attitude. Appropriate combinations of ignition time, burn duration, and attitude enable any reasonable target orbit to be achieved