The 28th Scientific Plenary Meeting of the EuroQol Group: Improving EQ-5D Instruments and Exploring New Valuation Techniques
The EuroQol Group comprises a network of international, multilingual, multidisciplinary researchers. Established in 1987, the Group first met to test the feasibility of jointly developing a standardized non-disease specific instrument for describing and valuing health-related quality of life. A process of shared development, local experimentation and lively discussion resulted in EQ-5D. EQ-5D™ is a standardized instrument for use as a measure of health outcome. Applicable to a wide range of health conditions and treatments, it provides a simple descriptive profile and a single index value for health status . It is now widely used in many countries around the world and has been translated into most major languages, with the Group closely monitoring the process (www.euroqol.org).
The EuroQol Group has a tradition of holding annual scientific plenary meetings. During the scientific sessions, members and co-workers of the Group, together with invited guests, present papers on topics that are of scientific and strategic interest to the Group. The aim of this article is to briefly report the developments in EQ-5D instruments and valuation methodology that were discussed at the Group’s 28th Scientific Plenary Meeting held in Oxford, England, on September 16-18, 2011.
The standard 3-level EQ-5D is a generic preference-based instrument for measuring health-related quality of life across a range of diseases and conditions. The generic nature of EQ-5D allows for capturing the impact of conditions or treatment on overall health-related quality of life and for comparison across different conditions and disease areas. EQ-5D includes a descriptive system that consists of five dimensions (mobility, self-care, usual activities, pain/discomfort and anxiety/depression) with three levels each (no problems, some or moderate problems and extreme problems). A number of national value sets have been derived for the 3-level EQ-5D. In addition to the descriptive system, EQ-5D includes a visual analogue scale on which the respondent rates their health from 0 to 100. The instrument can thus provide a profile measure of health, a VAS-based self-rating of health and a preference-based index score.
Substantial literature on EQ-5D has developed over the past two decades that supports the validity and reliability of the standard 3-level EQ-5D as a discriminative and evaluative measure in many conditions, as well as for measuring population health . Some have argued, however, that generic measures such as EQ-5D are insensitive or fail to capture important aspects of health in certain contexts. These limitations could be attributed to the descriptive system, i.e. the health dimensions and/or number of levels within each dimension, or the scoring algorithm. In response to the opportunity to improve the properties of the standard EQ-5D, the EuroQol Group embarked upon several projects. One initiative sought to expand the number of levels in each dimension of the standard EQ-5D, resulting in a new tool referred to as EQ-5D-5L. The EQ-5D-5L retains the original five dimensions, but has five levels of severity within each dimension: no problems, slight problems, moderate problems, severe problems and extreme problems . A second initiative seeks to experiment with additional dimensions of health-related quality of life.
In response to interest in measuring children’s and adolescents’ health-related quality of life, the EuroQol Group developed a child-friendly version of EQ-5D called EQ-5D-Y . The EQ-5D-Y descriptive system comprises five dimensions (mobility, looking after myself, doing usual activities, having pain or discomfort, feeling worried, sad or unhappy) with three levels each (no problems, some problems/a bit and a lot (of) problems/very). A proxy version of EQ-5D-Y, to be completed by the child’s parents or caregivers, will be available shortly.
Improving EQ-5D instruments
The results of several studies relevant to the above-mentioned initiatives were presented at the 2011 scientific plenary. A multinational parallel fielding study of the EQ-5D-3L and EQ-5D-5L compared the measurement properties of the two instruments in a wide range of patient populations (cardiovascular disease, respiratory disease, depression, diabetes, liver disease, personality disorders, arthritis and stroke). These early results indicate that the EQ-5D-5L appears to be a valid extension of the 3-level system but more research needs to be undertaken to investigate its discriminatory power and sensitivity to changes over time.
Another theme at the meeting was the EQ-5D-Y, which has been evaluated in various countries, especially in healthy populations. Preliminary studies to assess the psychometric properties of EQ-5D-Y in clinical samples are encouraging, and further investigation is planned to assess the instrument’s performance in different illness areas. The main challenge for the Group in regard to the EQ-5D-Y will be its application in economic evaluation. The formulation of a robust valuation methodology that is suitable for deriving social preferences for EQ-5D-Y health states will require further time and effort.
As with other generic instruments, the EuroQol Group is exploring the potential use of ‘bolt-ons’, i.e. items intended to capture additional dimensions of health-related quality of life that can be added to the standard 5-dimensional classification system. Systematic reviews on the validity and responsiveness of EQ-5D in various disease areas are useful in determining which bolt-ons might be useful, and which dimensions might be relevant. The (preliminary) results of studies exploring cognition, vision, hearing and tiredness as additional dimensions were presented at the meeting. Cognition was also identified as a potential additional dimension for EQ-5D-Y. A further issue is how such additional dimensions affect EQ-5D health state preferences. In order to answer these issues, the Group decided to develop a conceptual framework for the development of bolt-ons for EQ-5D instruments.
Exploring Valuation Techniques for EQ-5D-5L
The value sets for EQ-5D-3L that are currently available for a number of countries are based on the protocol of the Measurement and Valuation of Health (MVH) Group . In 1993 the MVH Group at the Centre for Health Economics at York University conducted the first large-scale national (UK) study to elicit direct valuations from the general public for 42 EQ-5D-3L health states using the time trade-off (TTO) method. Regression techniques were used to interpolate values for the 200 states for which no direct valuations were elicited . As the EQ-5D-5L instrument describes 3125 health states; the Group now faces a substantial challenge regarding valuation. A valuation protocol to estimate preferences for the health states described by the new instrument is being developed and provides a useful opportunity to improve on the existing 3L TTO valuation methodology for example by exploring lead time TTO  as well as exploring discrete choice (DC) modelling for health state valuation .
A multi-country pilot study has used a computer-based valuation technology to ensure standardized data collection across the eight countries involved. The technology was demonstrated at the scientific plenary and the first results of the pilot 5L valuation study were presented. It is hoped that the final version of the recommended valuation methodology for the EQ-5D-5L will become available during the first half of 2012. A key methodological issue discussed was whether this computer-based technology could replace an interviewer (i.e. CAPI versus face-to face interview). Previous research indicates the importance of trained expert interviewers during valuation tasks, so the Group will continue to explore this issue to ensure that the computer-based valuation task can be undertaken over a broad spectrum of the general population.
The EuroQol Group continues its endeavour to develop and refine instruments that will improve the measurement of health-related quality of life and to inform clinical decision making and health policy. The annual scientific plenary provides a forum for Group members to discuss study results and current issues as well as interact with invited experts in the area of health-related quality of life with the aim of stimulating collaborative work on new instruments and methodologies (see www.euroqol.org for further information).
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