REVIEW ARTICLE
EQ-5D and the EuroQol Group: Past, Present and Future
Nancy J. Devlin
1
•
Richard Brooks
2
Published online: 13 February 2017
The Author(s) 2017. This article is published with open access at Springerlink.com
Abstract Over the period 1987–1991 an inter-disciplinary
five-country group developed the EuroQol instrument, a
five-dimensional three-level generic measure subsequently
termed the ‘EQ-5D’. It was designed to measure and value
health status. The salient features of its development and its
consolidation and expansion are discussed. Initial expan-
sion came, in particular, in the form of new language
versions. Their development raised translation and
semantic issues, experience with which helped feed into the
design of two further instruments, the EQ-5D-5L and the
youth version EQ-5D-Y. The expanded usage across clin-
ical programmes, disease and condition areas, population
surveys, patient-reported outcomes, and value sets is out-
lined. Valuation has been of continued relevance for the
Group as this has allowed its instruments to be utilised as
part of the economic appraisal of health programmes and
their incorporation into health technology assessments. The
future of the Group is considered in the context of: (1) its
scientific strategy, (2) changes in the external environment
affecting the demand for EQ-5D, and (3) a variety of issues
it is facing in the context of the design of the instrument, its
use in health technology assessment, and potential new
uses for EQ-5D outside of clinical trials and technology
appraisal.
Key Points for Decision Makers
The EQ-5D portfolio of health status instruments,
EQ-5D-3L, EQ-5D-5L and EQ-5D-Y, is the product
of nearly 30 years of development and adaptation.
These instruments have been applied in a variety of
health sector settings, in patient-reported outcome
exercises, in population health studies, and in health
technology assessment.
A wide-ranging programme of research studies is in
process to adapt and further develop the EuroQol
portfolio.
1 Introduction
The EQ-5D is a well-known and widely used health status
instrument. It was developed by the EuroQol Group in the
1980s to provide a concise, generic instrument that could
be used to measure, compare and value health status across
disease areas.
The initial Group participants were from a variety of
professional backgrounds with a common interest in the
measurement of health status and in the outcomes of
healthcare programmes. The development of the instru-
ment was motivated in part by health economics consid-
erations, i.e. to create a way of measuring health status to
inform resource allocation decisions by enabling the
application of cost-effectiveness analysis (CEA) to health
care. Aiming at valuing health states gave the potential for
the instrument to estimate quality-adjusted life-years
(QALYs) for use in CEA.
Electronic supplementary material The online version of this
article (doi:10.1007/s40258-017-0310-5) contains supplementary
material, which is available to authorized users.
& Nancy J. Devlin
ndevlin@ohe.org
1
Office of Health Economics, London SW1 3QT, UK
2
EuroQol Group, Rotterdam, The Netherlands
Appl Health Econ Health Policy (2017) 15:127–137
DOI 10.1007/s40258-017-0310-5
Valuation, however, was not the sole consideration of
the Group, and this has been confirmed by the incorpora-
tion of EQ-5D into clinical trials, observational studies,
population health surveys and, more recently, into routine
outcome measurement via Patient Reported Outcome
(PRO) measures in the healthcare sector.
The aims of this paper are to: (1) describe the prove-
nance and development of the EQ-5D by the EuroQol
Group, and to highlight the factors that contributed to its
widespread use as a generic instrument; (2) outline the
current state of play with respect to the use and application
of EQ-5D and further development of the suite of EQ-5D
instruments, and (3) consider the future of the EQ-5D,
including the research directions signalled by the Group,
and the challenges that might shape its future use and
development.
2 A Brief History of the EQ-5D
Detailed histories of the EuroQol Group and its develop-
ment of the EQ-5D are available elsewhere [1–3]. In this
paper the focus is on the following questions: Why was the
EQ-5D initially developed? How did its use and applica-
tion evolve? How will the EuroQol Group proceed?
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 devel-
opment 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 alter-
native 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 objec-
tives 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 dimen-
sions 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 activi-
ties 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-dimen-
sional health status instrument after some 3 years of devel-
opment [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 instru-
ment,’ it was formally designated ‘EQ-5D’ in 1995. The
descriptive system defined (3
5
) = 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, mag-
nitude 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-
128 N. J. Devlin, R. Brooks
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 delib-
eration about whose values (experts, patients, or the gen-
eral public) should be used. It is important to note that
these efforts preceded—by over a decade—the establish-
ment of formal health technology assessment (HTA)
organisations and processes, so the EuroQol Group was
operating in largely uncharted territory.
2.2 Cons olidation and Expa nsion
The two and a half decades which followed the establish-
ment of the EQ-5D in 1990 were characterised by contin-
ued 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 ques-
tionnaire, 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 addi-
tional 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 evalu-
ation, 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 valua-
tions. 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 EuroQo l 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.
EQ-5D and the EuroQol Group: Past, Present and Future 129
The next development was the appointment of a Busi-
ness Manager and a Management Assistant in 1993 and
1994, respectively. In 1994, inquiries from the pharma-
ceutical 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 Associa-
tion and Foundation, monitored by a Board and Executive
Committee, were established under Dutch law, and a
Business Management office set up in Rotterdam.
Critical to understanding the current nature of the
EuroQol Group was the business model which emerged
from this process of formalising the organisation in the
mid-1990s. The key features are:
• The EuroQol Group in all its activities is a not-for-
profit organisation.
• Users must register use of the instrument (copyright to
which was first asserted in 1990 and was formally
transferred to the Association upon its establishment in
1995).
• Commercial, for-profit users are changed a licence fee
for the use of EQ-5D.
• Not-for-profit academic users are able to use EQ-5D
free of charge.
• The EuroQol Group comprises both a business unit and
an international, multi-disciplinary collaborative net-
work of researchers—the members of the EuroQol
Group—who drive forward the science surrounding the
EQ-5D.
This combination of arrangements proved an appropri-
ate model for promulgating the use of EQ-5D and gener-
ated 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 pre-
sent. However, there have been important related devel-
opments, 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.
2.4.1 Translation and Version Management
From the outset English had been used as the working or
‘source’ language for the EQ-5D, and the instrument was
simultaneously constructed in Finnish, Dutch, Swedish and
Norwegian. Draft translation guidelines were first devel-
oped in 1994, and in 1996 expanded guidelines were
implemented, overseen by a Translations Committee, set-
ting in place a standard forwards-and-backwards transla-
tions process which supported the development of a large
number of language versions in subsequent years.
When EQ-5D spread to new languages the process of
translation pointed to difficulties in language usage and to
differences in the conceptualisation of EQ-5D dimensions
and items across countries and languages. This led the
Group to consider more closely the meanings of concepts
and the related wording used in EQ-5D, not least in Eng-
lish. The Translation aspect of the EQ-net project provided
the opportunity for substantive work on these matters. A
definition of EQ-5D concepts was provided and a series of
recommendations for further research was made [9]. Also
generated were a taxonomy of definitions of EQ-5D con-
cepts, SOPs and detailed translation guidelines. A detailed
account of translating EQ-5D into 11 European languages
provided an insight into the translation process, and the
challenges involved [10].
In 2009 a Version Management Group (subsequently
Committee) was established, with responsibilities for
reviewing new language versions, responding to client and
translation agency queries, updating essential documenta-
tion, and implementing systems aimed at improving ver-
sion control and management. This group has
responsibility not just for different language versions, but
also for testing and approving electronic versions of the
EQ-5D (tablet, web-based, PDAs), demand for which has
risen [11].
2.4.2 EQ-5D-5L
Notwithstanding the strong uptake in the use of EQ-5D,
particularly in HTA, concerns about its adequacy as a
measure of HRQoL have been voiced. There continued to
be lively debate within the EuroQol Group going back to
1994 [12] regarding the three-level structure of the
response options (no, some, extreme problems/unable to)
and whether this was associated with ceiling effects and a
lack of sensitivity to changes in health. Kind and Macran
fuelled that debate, reporting an investigation of a five-
level version of the core five dimensions [13]. In 2005,
sufficient momentum on this issue had built such that a
EuroQol Group task force was established to consider an
increased level descriptive system, in response to concerns
130 N. J. Devlin, R. Brooks
about the perceived lack of sensitivity of the EQ-5D and
ceiling effects in the descriptive system.
In 2006, after considerable debate and pre-studies about
whether to go for a four- or five-level version, it was decided
to recommend the development of a five-level version of the
instrument, while retaining the same core five dimensions. In
addition ‘confined to bed’ was replaced by ‘unable to walk
about’ to increase sensitivity of the mobility dimension.
Results from initial studies testing five-level versions of the
EQ-5D showed increased reliability, sensitivity (discrimi-
natory power) and feasibility [14–17].
As with the original EQ-5D, the intention behind the new
five-level version was that it be accompanied by value sets.
For that reason, rather than assign the additional two levels as
‘unlabelled’ response options between no and some, and some
and extreme, problems, it was felt that all five levels required
labels. Labels were selected following the results of semantic
testing inEngland,Spain and France [18, 19], and the resulting
labels translated into other languages. Two features of this
process can be highlighted. First, the labels were chosen for
UK English, Spanish and French, based on an exhaustive
process of response scaling among a wide range of potential
labels selected from the literature and existing PRO ques-
tionnaires, together with follow-up focus group research to
explore respondents’ understanding of those labels in the three
countries. Second, once the labels had been decided on, the
UK English, Spanish and French versions could then be used
as source content for any new language versions required.
These are produced following the EuroQol Group’s transla-
tion methodology, which also includes in-depth semantic
testing of all wording in the target language, with a particular
focus on the severity labels (see [11]).
The new instrument was approved as an official Euro-
Qol instrument in 2009. From that point, the five-level
instrument has been referred to as the EQ-5D-5L, and the
original EQ-5D has been re-named the EQ-5D-3L. The
research underpinning the EQ-5D-5L is summarised in
Herdman et al. [20], including consideration of the map-
ping of health states from one system to the other.
2.4.3 EQ-5D-Y
The EQ-5D was, implicitly, designed for self-completion
by adults. However, HTA bodies and other healthcare
decision-makers frequently make decisions regarding
treatments for children and young people. From 1998,
interest grew in the possibility of using the EQ-5D, or
adapting it in some way, for use in younger people. An
initial ‘child friendly’ version of the EQ-5D, reported in
2002 [21], was followed by research efforts in a range of
countries. A task force, established in 2006, coordinated
these efforts, and considered issues regarding what
dimensions to include and how to label them, what number
of levels to use, proxy completion, what age ranges to
target, and how to value children’s health states [22, 23].
These efforts culminated, in 2009, in approval of a ‘youth’
version, the EQ-5D-Y, as an official EQ-5D product. The
EQ-5D-Y retained the same five-dimension, three-level
format of the EQ-5D, but dimensions were described in more
appropriate language as: mobility (walking about); looking
after myself; doing usual activities; having pain or discom-
fort; feeling worried, sad or unhappy. (EQ-5D-Y appears as
Appendix 5 in the online Supplementary Material).
EQ-5D-Y is suitable for self-completion by children
aged 8–11 years; it is also recommended for use at ages
12–15 years, although use of the EQ-5D adult version
might be possible in some circumstances. The EQ-5D adult
version is recommended for those aged 16 years and over.
2.4.4 Protocols for Value Sets
Despite the widespread utilisation of the MVH tariff for
QALY purposes there was no ‘official’ valuation protocol
or consensus view within the EuroQol Group about valu-
ation methods to be used in producing value sets. Different
research teams adapted the MVH study design in various
ways, making different choices about, for example, the
number and selection of states to value; ‘exclusion rules’
applied to the data; and so on [24]. This limited the com-
parability of the data. This was addressed in 2009 at a
meeting in Paris, where a modified version of the MVH
study design was endorsed (‘the Paris protocol’) for use in
EQ-5D-3L value set studies. Included among the changes
incorporated at that point was dropping ‘unconscious’ from
the states to be valued in such studies.
Having developed the EQ-5D-5L, the EuroQol Group
decided this presented an important opportunity to improve
valuation methods and to promote a consistent approach to
valuing EQ-5D-5L by providing an official protocol and
study design. Interim values for the EQ-5D-5L were
available from a ‘crosswalk’ study: six countries adminis-
tered both the five-level and three-level versions in parallel,
from which a crosswalk enabled EQ-5D-5L profiles to be
mapped to EQ-5D-3L profiles, and values applied from
existing EQ-5D-3L value sets [25]. At the same time, a
series of methodological studies were undertaken, explor-
ing a variety of approaches to both TTO and discrete
choice experiments (DCE). The latter method had been
investigated in 2008 using the three-level version [26].
Work was also undertaken to develop thesoftware to allow
these methods to be implemented in computer-assisted
personal interviews (CAPI). A prototype protocol, incor-
porating these approaches, was piloted in a multi-country
study [27].
Following further testing and refinement, the interna-
tional protocol for valuation of EQ-5D-5L was launched
EQ-5D and the EuroQol Group: Past, Present and Future 131