EQ-5D and the EuroQol Group: Past, Present and Future

2.1 The Provenance of the EQ-5D

The EuroQol Group started its journey in 1987: 14 people met to exchange ideas about how to approach the development of a health status measurement instrument. One of the motivations for doing so was to assist healthcare decision-makers to make resource allocation decisions informed by evidence on the cost-effectiveness of alternative treatments.

From the outset the Group therefore sought a ‘common core’ of basic information or key attributes to be collected by all investigators in a standardised way. This came to be crystallised in the following set of objectives: (1) To develop a generic instrument to describe and value health-related quality of life (HRQoL), providing both a descriptive profile and an overall index. (2) It was to be a standardised tool to facilitate the collection and pooling of a common data set. (3) It was to be suitable for self-completion and acceptable for use in postal surveys (at that point, a common mode of data collection). These objectives in turn led to a number of requirements for the descriptive system: (1) dimensions should be relevant to patients across the spectrum of health care and to members of the general population. (2) It should be simple—using as few dimensions as possible, with as few levels as possible within each dimension. (3) It should be amenable to self-completion in a range of settings, should be simple enough not to require detailed instructions, and should only take a couple of minutes to complete.

The Group discussed various alternatives with respect to the selection of dimensions, including a survey of patients and the general population, to identify common dimensions of relevance to all groups. Since the selection of dimensions from such an exercise would still involve value judgments, the Group members decided instead to draw on their own expertise by undertaking a detailed review of other available generic health measures. Contrary to expectations, the dimensions suggested for inclusion as a result of this exercise were broadly similar, differing more on dimension nomenclature than on content. General agreement settled on the following: mobility, daily activities and self-care, psychological functioning, social and role performance, and pain or other health problems [4]. In addition, as the Group was multilingual, the classification system descriptors were selected from the outset with a number of languages in mind, rather than a source version being translated into other languages.

The EuroQol Group publicly introduced a six-dimensional health status instrument after some 3 years of development [1]. However, by the time of its publication, further empirical testing had already led the instrument to be further refined to five dimensions—mobility, self-care, usual activities, pain/discomfort and anxiety/depression—each with three levels. Originally named the ‘EuroQol instrument,’ it was formally designated ‘EQ-5D’ in 1995. The descriptive system defined (3⁵) = 243 different states. Two further states were initially included in valuation work: unconscious and dead (both states undefinable in terms of the descriptive system). With the development of the five-level version EQ-5D-5L (see Sect. 2.4), the three-level version was re-designated EQ-3D-3L. (Both versions appear as Appendices 1–4 in the online Supplementary Material).

Initial EQ-5D valuation work employed ranking, magnitude estimation and visual analogue scale (VAS) approaches, but VAS was quickly established to be the valuation approach of choice. At that point in time, other methods were in their infancy, such as time trade-off (TTO), or had not been much applied in the health status context, such as the standard gamble (SG). It was for that reason that the EQ VAS was introduced as part of the EQ-5D questionnaire right from the start: its initial role was actually as a warm-up task for the VAS valuation tasks, and only later was its potential usefulness as a self-reported global measure of overall health recognised [5].

While these early efforts converged on a descriptive system in what was a relatively short period of time, a considerable and rapidly expanding research programme continued, to test the reliability and validity of the EQ-5D in populations and patients. This was accompanied by an extensive programme of research on the valuation of EQ-5D, to test the effect on values of the stated duration of states; the visual presentation and positioning on the VAS scale; the selection of the states to be valued; and deliberation about whose values (experts, patients, or the general public) should be used. It is important to note that these efforts preceded—by over a decade—the establishment of formal health technology assessment (HTA) organisations and processes, so the EuroQol Group was operating in largely uncharted territory.

2.2 Consolidation and Expansion

The two and a half decades which followed the establishment of the EQ-5D in 1990 were characterised by continued research and development, considerable growth in the use of the EQ-5D in healthcare decision-making, and ongoing efforts to develop both additional instruments within the EQ-5D framework and improved methodologies for eliciting and modelling health state values. There were also significant changes in the EuroQol Group as an organisation—it grew, formalised its processes and put in place the business model which exists today.

First, it is noteworthy that, apart from some minor wording and design changes to the original EQ-5D questionnaire, what is now termed EQ-5D-3L has remained more or less unchanged from 1990 to the present day. While there has been ongoing experimentation with additional dimensions and the number of levels, as discussed below, these changes have not been incorporated in the EQ-5D-3L instrument itself.

This stability in the EQ-5D 3L instrument has had a number of consequences. After two and a half decades of use and research, there is a substantial back-catalogue of studies, evidence and EQ-5D data available to support new investigations. Research has built upon and developed knowledge of the use and analysis of EQ-5D data. From the perspective of its application in HTA, this stability can facilitate consistent decisions over time.

Expansion in the use of EQ-5D post-1990 came in a number of ways. First, the demand for EQ-5D data and the accompanying value sets increased markedly as HTA organisations became established in healthcare systems around the world. Second, considerable resources were devoted to expanding the number of EQ-5D language versions, facilitating global use of the instrument. Third, there was a rapid increase in the number of applications for licences to use the EQ-5D in a variety of medical and health sector settings, and pharmaceutical companies began to use the instrument in increasing numbers, reflecting the requirement of HTA bodies to supply evidence on QALYs.

In the valuation context a noteworthy development came from the Measurement and Valuation of Health (MVH) study, led from the University of York in the early 1990s, in the form of a set of EQ-5D ‘tariffs’ based on TTO values from the general public which could be used to generate QALYs. The tariff (value set) produced from the MVH study [6] became very widely applied in economic evaluation, both in the UK and in other countries (and continues to be used today). This subsequently led to a number of other countries adopting similar methods for collecting and modelling their own value sets.

Also of significance for the progress of the EuroQol Group was the EQ-net project of 1998–2001 funded by the Biomed programme of the European Commission. This project provided the opportunity to put members’ research work into a more structured context, with most of the efforts of the Group devoted to it during this 3-year period.

The tasks involved were divided into three sub-projects: Translation, Valuation and Application. In addition, the communication of information and knowledge about EQ-5D was addressed, with detail on all aspects of the project subsequently being published in book form [7]. Since the main aim of the project was to harmonise data on the valuation of EQ-5D health states collected in different European countries, considerable effort was put into the Valuation sub-project. Two databases were established, one containing VAS valuations and the other TTO valuations. The Application sub-project produced standard operating procedures (SOPs) for the design, analysis and reporting of EQ-5D in clinical, economic and population studies, which were included in the book alongside guidelines for differing modes of administration of EQ-5D: versions for observer, face-to-face administration, proxy and telephone. The work accomplished in the Translation sub-project is treated separately in Sect. 2.4 below.

Essentially the EQ-net project stimulated the further development and dissemination of EQ-5D, which fed into the scientific programmes pursued in the new millennium.

2.3 The Evolution of the EuroQol Group as an Organisation

As use of the instrument grew, the relatively simple club-like nature of the early Group necessarily evolved into more formalised arrangements. The use of EQ-5D in HTA (particularly by NICE in the UK, which, in 2004, identified the EQ-5D as its preferred instrument [8]) led to increased demand from pharmaceutical companies wanting to include EQ-5D data in HTA submissions. This presented an opportunity to license that use and to generate revenue. A key period in the evolution of the Group in this respect was 1993/94. Up until 1993, the activities of the Group were supported exclusively by the initial small group of members and their institutions, both by contributing their time and, occasionally, by contributing financial support to the enterprise.

The next development was the appointment of a Business Manager and a Management Assistant in 1993 and 1994, respectively. In 1994, inquiries from the pharmaceutical industry began to be directed through the business office, which was instructed to develop a pricing policy. This marked the beginning of modest revenue generation, in keeping with the not-for-profit nature of the Group.

This was quickly followed by setting in place legal arrangements. In 1995 the formal organisational (and legal) structure for the Group comprising the EuroQol Association and Foundation, monitored by a Board and Executive Committee, were established under Dutch law, and a Business Management office set up in Rotterdam.

This combination of arrangements proved an appropriate model for promulgating the use of EQ-5D and generated revenue with which to support and fund research. Group membership expanded—currently at around 80—and has become an international rather than a European network. In addition, with some members having a career-long association with the Group there has been a great deal of continuity of endeavour.

2.4 Instrument Development

In Sect. 2.2 we noted that the EQ-5D-3L as an instrument has remained largely unchanged from 1990 until the present. However, there have been important related developments, including many new language versions, newly derived EuroQol Group instruments and systematic approaches to valuation for use in producing value sets. We briefly review the principal developments below, after outlining translation and version management issues.

3.1 Availability and Use of EQ-5D Instruments

The position in 2016 with respect to translations, as detailed on the EuroQol website (http://www.euroqol.org), is 176 EQ-5D-3L and 138 EQ-5D-5L language versions. In addition alternative available formats comprise: proxy, telephone interview, IVR (interactive voice response) via telephone, web, tablet and PDA.

The number of studies using the EQ-5D suite of instruments, registered with the EuroQol Group, totalled over 17,000 by 2015. These comprised over 80 clinical areas and 40 programmes and settings. For studies in the top 25 clinical areas, apportioned by type of study, the figures were: interventional studies (including randomised control trials) 33%, observational studies 28%, surveys 15% and other studies 24%. Programmes and settings included, inter alia, surgical procedures, general practice and primary care, hospital waiting lists, physiotherapy and rehabilitation.

3.2 New and Emerging Uses of EQ-5D

EQ-5D instruments continue to be used to measure the health status of patients, and to provide evidence on the cost-effectiveness of healthcare technologies, and in population health surveys to examine the health of the general public.

More recently, there has also been growing use of the EQ-5D as part of routine, administrative data collection in healthcare systems. In 2009, NHS England introduced its Patient Reported Outcome Measures (PROMs) programme: the EQ-5D, alongside condition-specific PROs, is collected from all NHS patients before and after elective surgery for hip and knee replacement, varicose veins and hernia repair [31]. These data are used to monitor the performance of healthcare providers, to incentivise quality by linking reimbursement to performance, and to inform patient choice of provider. Similar uses of EQ-5D are underway, or planned, in the healthcare system in Sweden, and in Alberta Health Services in Canada. The private healthcare sector also uses EQ-5D—for example, Southern Cross, New Zealand’s largest private insurance company, require providers to collect these data as a means of checking the quality of care they fund. These PROMs programmes generate large-scale data—they cover entire populations, rather than samples, of patients, and are generating powerful real-world insights on treatment and provider effectiveness, beyond the confines of clinical trials. EQ-5D has thus become part of the ‘big data’ revolution in health care [32]. This emerging use poses new challenges for issues such as data sharing and methods to achieve comparability of responses.

4.1 The Scientific Strategy of the EuroQol Group

One aspect of these priorities is the intention to revisit the descriptive system. Systematic reviews of the use of EQ-5D indicate its acceptability as a measure of health status in most disease areas [33], although there are some types of health problems where the EQ-5D appears not to perform well, such as problems with hearing and vision.

Nevertheless, there have been considerable advances in health status measurement and the science of PRO instrument development since the initial development of EQ-5D in the late 1980s, hence the Group considered that it would be appropriate at this juncture to explore whether the instrument could be improved and its performance enhanced and, if so, in what ways. The Group has therefore signalled its intention to undertake a ‘fundamental’ research programme to address the conceptual and empirical basis for the core instrument, as indicated in Table 3. If evidence provides clear support for making changes to the conceptual model or to instrument content, this will lead to discussion around whether a new version of the instrument should be developed and the methods for doing so. This would clearly be a long-term research endeavour and an important part of the discussion would be the implications of making any significant changes.

The Group is also undertaking experiments on another approach to enhancing instrument performance in certain population sub-groups, i.e. through the use of ‘bolt-on’ dimensions. In its simplest form, this retains the core five dimensions, but adds one (or more) dimension to capture aspects of health which may not adequately captured by these dimensions. Some initial experiments with bolt-ons have been undertaken for vision, hearing, tiredness, psoriasis and sleep [34, 35, 36]. At a descriptive level, the introduction of bolt-on dimensions can add to the richness of respondent profile data. However, this approach raises non-trivial issues, especially in connection with the consequences for health state valuations in the expanded instruments [33, 36].

4.2 Changes in the External Environment Affecting the Demand for EQ-5D

The future of the EQ-5D is closely linked to developments in healthcare systems with respect to measuring outcomes, and how outcomes data are used by decision-makers. EQ-5D has been a cornerstone of QALY-based HTA systems and its continued use in that context depends on the extent to which QALYs and cost-effectiveness analysis remain an integral part of HTA. Critiques of QALYs have long existed and continue to generate debate. In recent years, there has been growing interest in the inclusion of other elements of value that might be missed by QALYs, such as, inter alia, patients’ preferences regarding their treatment, benefits to caregivers and social benefits from increased productivity. It has also been suggested that there needs to be a shift to new measurement paradigms—such as assessing treatment benefits in terms of gains or losses in subjective wellbeing. If such suggestions gain traction EQ-5D may become less important in this context [37, 38, 39, 40].

Notwithstanding the growing interest in going ‘beyond QALYs’, it seems likely that the QALY will remain a central part of HTA for some time to come—in part because of the challenges in implementing a radically different approach and the difficulty in making such a fundamental change, and in part because of the lack of any other credible measurement approach to ‘value’ which could replace it.

Furthermore, HTA systems are being established in ever more parts of the world—South America, Africa, Asia—so demand for EQ-5D instruments seems likely to continue to grow as these areas of the world require local evidence to inform their decisions.

EQ-5D usage expanded because the instrument provided a simple and effective means to compare the impact of disease and its treatment across different disease areas and patient groups, and of incorporating societal preferences for health states into those comparisons. A further factor which may affect future demand for EQ-5D is the rise of condition-specific instruments accompanied by utilities: this means that utility becomes the common denominator for comparison of QALYs (providing utilities are generated using consistent methods, and give commensurate measures of utility), not the generic health state descriptive system itself.

Finally, demand for EQ-5D will also be affected by its growing use outside of HTA, to inform different kinds of decisions. This includes the potential for EQ-5D to have a role in clinical settings, as part of patient decision aids [41] and the growing inclusion of EQ-5D in routine, administrative data in healthcare delivery, as reported in Sect. 3.2.

These new uses of EQ-5D may have implications for the future development of methodologies to support its use. For example, where EQ-5D is used to monitor the performance of providers, appropriate case-mix adjustment methods become crucial, as does an understanding of how much variation in performance is ‘normal’. Given the large scale of health system-wide data collection of EQ-5D data in PROMs programmes, a better understanding of what constitutes a minimally important difference in EQ-5D arguably also becomes more important.

Further, these uses of EQ-5D serve quite different types of healthcare decisions and decision-makers (e.g. patients’ decisions about what treatments to choose, regulators’ monitoring of quality standards of healthcare providers) than those that have conventionally been the focus of EQ-5D (e.g. budget holders’ decisions about how resources are allocated in the healthcare sector or HTA decisions about whether new technologies are good value for money). This potentially has implications for the way EQ-5D profile data are summarised: the use of ‘value sets’ reflecting the preferences of the general public has a normative justification specific to the use of those data in resource allocation decisions [42]. In contrast, judgements about what constitutes ‘good quality health care’, or individual patients’ choices between different treatments, might suggest a role for patient preferences, rather than those of the general public, in summarising and analysing EQ-5D data [43]. These are areas for future exploration.