Measuring health and well-being for economic evaluation

The last two decades have seen an increasing use of economic evaluation to inform resource allocation in health care systems around the world (e.g. NICE). A core issue for economic evaluation is the way the benefits of health care are measured and valued. A widely used technique of economic evaluation in health care has been cost effectiveness analysis using Quality Adjusted Life Years (QALYs) to assess effectiveness in units that are comparable across health care interventions. Commonly used methods for putting the `Q´ into the QALY are generic preference-based measures of health, such as the EQ-5D, SF-6D, HUI2 and the HUI3. These generic measures have been adopted by agencies such as NICE to populate their models of the cost-effectiveness of interventions.

This HEDS programme of research is composed of various related projects funded from a range of sources; including: MRC, NIHR and Pharmaceutical companies. The overall aim of the programme is to address the key questions of what should be valued (e.g. health or broader notions of well-being); how health and well-being should be described; how health and well-being should be valued; who should do the valuing and how to develop new measures.

Generic preference-based measures of health

Following on from the development of the SF-6D, research has continued with the replication of this work in countries around the world (China, Japan, Portugal, Brazil, Australia and Singapore). The research team has also been pursuing new methods for analyzing preference data, including the use of Bayesian methods. Several HEDS staff members are members of the EuroQoL Group. Members of HEDS are also involved in an MRC funded project, the Preparatory study for the Re-evaluation of the EQ-5D Tariff (PRET). Staff at ScHARR have also developed a new measure for children using mixed methods analysis.

Reviewing the appropriateness of generic measures

Health economists have often favoured generic measures in order to allow cross programme comparison. However this pre-supposes that they are valid and responsive in all groups of patients. We are undertaking a number of reviews of the validity of generic measures in vision, mental health, diabetes and cancer.

What to do when generic measures are not available

Many pivotal studies of new health care interventions do not use one of the generic preference-based measures due to concerns about patient burden or validity, but other non-preference based measures of health (e.g. condition specific measures). One solution to this problem is to estimate functions that `map´ or `cross-walk´ condition specific measures onto a generic preference-based measure. Research at ScHARR has critically reviewed these methods and examined the policy implications of errors in these models. A team at ScHARR also has just completed a research project for MRC examining a new method for mapping based on using preference data.

Development of condition-specific preference-based measures of health

Where generic measures are not regarded as appropriate, then the alternative is to develop a specific measure more relevant to the condition. This can involve either developing news measures from scratch or modifying an existing non-preference based measure for this purpose. Staff at ScHARR have developed measures from scratch for people with leg ulcers, and are currently working on a measure for children with amblyopia and a measure for pressure ulcers. A mixed methods approach including qualitative research with patients and psychometric testing has been used to develop the health states.

To make the most of available evidence, a better strategy might be to develop a preference-based measure from an existing and widely accepted condition specific measure. We are currently working on developing preference-based measures for dementia, cancer and common mental health problems and have completed measures for asthma and overactive bladder. This work has involved the application of a range of psychometric methods (i.e. Rasch analysis) to derive health state classifications and then surveys to obtain general population values for calculating QALYs. We have also just completed the COSMeQ project examining the methodological issues in developing condition specific preference-based measures.

Valuation techniques

Conventional techniques for valuing health states have been Time Trade-Off (TTO), Standard Gamble (SG) and Visual Analogue Scaling (VAS). There are concerns that TTO and SG especially are too complex in vulnerable groups and that the values generated may be distorted by extraneous factors such as time preference and loss aversion that making it difficult to ascertain the value for health per se for calculating QALYs. For this reason we have been looking at the use of ordinal methods, such as ranking and Discrete Choice Experiments (DCE), for valuing health states in this programme. The key contribution has been to develop methods for valuing health states on the full health-dead scale required for calculating QALYs. There have also been concerns with the way states worse than dead are handled in conventional TTO and we have been involved in the development and testing of a new `lead time´ TTO.

Whose values?

Our work has provided further evidence that the values put on health states by members of the general public and patients diverge. The more original contribution has been to show that people experiencing the state (e.g. patients) place a different weight on the dimensions of health to members of the general public trying to imagine what the state is like. One finding, for example, has been that people in the states place a higher relative value on mental health compared to physical health.

The divergence between patient and general public values has been explained in terms of adjustment and coping mechanisms, at least to physical health problems. A PhD has recently been completed exploring the impact on health state values of providing better information to general population respondents on these processes. We are also currently undertaking projects examining how values differ for patients and general population for epilepsy health states, and how values differ for patients, carers and general population for dementia health states.

Health or well-being?

An important question is whether the NHS should be primarily concerned with promoting health, or some broader notion of well-being. We are collaborating in the development of broader measures, including a preference-based measure of capability (ICECAP) and a measure for social care (OSCAR). We have also examined the relationship between health and broader measures of well-being in a micro-study of patients experiencing health change using mixed methods research. Future work will include the development of a well-being scale that can be used to calculate QALYs.

ScHARR is a major partner in CWiPP, the University Centre for Health and Well-being in Public Policy that focuses beyond conventional health and encourages collaboration between departments in the University in this exciting area of public policy research.