The EQ-5D (Euroqol) is a valid generic instrument for measuring quality of life in patients with dyspepsia.

Abstract

There is little information of the validity of generic instruments in measuring health-related quality of life (HRQOL) in patients with dyspepsia. We aimed to assess the reliability and validity of the EQ-5D, a brief and simple instrument, in measuring HRQOL in adult patients with dyspepsia.
Consecutive adults with dyspepsia attending the Gastroenterology clinic in a tertiary referral center were interviewed with the EQ-5D (both English and Malay versions), the short-form Nepean Dyspepsia Index (SF-NDI), the SF-36 and Leeds Dyspepsia Questionnaire (LDQ). Known-groups and convergent construct validity were investigated by testing hypotheses at attribute and overall levels. A repeat telephone interview was conducted 2 weeks later to assess test-retest reliability.
A total of 113 patients (mean (SD) age: 53.7 (14) years; 49.5% male; 24.8% Malays, 37.2% Chinese; 70.8% functional dyspepsia) were recruited. Response rate was 100% with nil missing data. Known-groups validation revealed 20/26 hypotheses fulfillment. Patients with more severe dyspepsia reported more problems with their usual activity (p = 0.07) and pain (p = 0.06) and demonstrated lower median VAS scores (60 vs 70, p = 0.002) and EQ-5D utility scores (0.72 vs 0.78, p = 0.002). Those reporting problems in various EQ-5D dimensions had significantly lower scores in relevant SF-36 and SF-NDI dimensions. The overall EQ-5D utility score also demonstrated good correlation with the SF-36 summary physical and mental scores and the SF-NDI total score. Intraclass correlation coefficient for test-retest reliability was 0.66 (95% CI = 0.55 - 0.76).
The EQ-5D is an acceptable, valid and reliable generic instrument for measuring HRQOL in adult patients with dyspepsia.

Full text

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BioMed Central
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BMC Gastroenterology
Open Access
Research article
The EQ-5D (Euroqol) is a valid generic instrument for measuring
quality of life in patients with dyspepsia
Sanjiv Mahadeva*†1, Hwee-Lin Wee†2, Khean-Lee Goh1 and
Julian Thumboo2,3
Address: 1Division of Gastroenterology, Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia,
2Department of Rheumatology and Immunology, Singapore General Hospital, Singapore and 3Department of Medicine, National University of
Singapore, Singapore
Email: Sanjiv Mahadeva* - sanjiv@ummc.edu.my; Hwee-Lin Wee - phawhl@nus.edu.sg; Khean-Lee Goh - klgoh56@tm.net.my;
Julian Thumboo - julian.thumboo@sgh.com.sg
* Corresponding author †Equal contributors
Abstract
Background: There is little information of the validity of generic instruments in measuring health-
related quality of life (HRQOL) in patients with dyspepsia. We aimed to assess the reliability and
validity of the EQ-5D, a brief and simple instrument, in measuring HRQOL in adult patients with
dyspepsia.
Methods: Consecutive adults with dyspepsia attending the Gastroenterology clinic in a tertiary
referral center were interviewed with the EQ-5D (both English and Malay versions), the short-form
Nepean Dyspepsia Index (SF-NDI), the SF-36 and Leeds Dyspepsia Questionnaire (LDQ). Known-
groups and convergent construct validity were investigated by testing hypotheses at attribute and
overall levels. A repeat telephone interview was conducted 2 weeks later to assess test-retest
reliability.
Results: A total of 113 patients (mean (SD) age: 53.7 (14) years; 49.5% male; 24.8% Malays, 37.2%
Chinese; 70.8% functional dyspepsia) were recruited. Response rate was 100% with nil missing data.
Known-groups validation revealed 20/26 hypotheses fulfillment. Patients with more severe
dyspepsia reported more problems with their usual activity (p = 0.07) and pain (p = 0.06) and
demonstrated lower median VAS scores (60 vs 70, p = 0.002) and EQ-5D utility scores (0.72 vs
0.78, p = 0.002). Those reporting problems in various EQ-5D dimensions had significantly lower
scores in relevant SF-36 and SF-NDI dimensions. The overall EQ-5D utility score also
demonstrated good correlation with the SF-36 summary physical and mental scores and the SF-
NDI total score. Intraclass correlation coefficient for test-retest reliability was 0.66 (95% CI = 0.55
– 0.76).
Conclusion: The EQ-5D is an acceptable, valid and reliable generic instrument for measuring
HRQOL in adult patients with dyspepsia.
Published: 12 March 2009
BMC Gastroenterology 2009, 9:20doi:10.1186/1471-230X-9-20
Received: 18 December 2008
Accepted: 12 March 2009
This article is available from: http://www.biomedcentral.com/1471-230X/9/20
© 2009 Mahadeva et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Background
Dyspepsia, a collection of upper gastrointestinal symp-
toms due to various causes, is a common problem world-
wide [1]. As most patients with dyspepsia have functional
disease, the treatment of which remains unsatisfactory at
present [2], health-related quality of life (HRQOL) meas-
urement has become an important clinical objective in
the assessment of new therapies for this condition [3].
Several disease-specific HRQOL instruments for dyspepsia
have been developed including the quality of life in reflux
and dyspepsia (QOLRAD) questionnaire [4] and the
Nepean Dyspepsia Index [5], both of which are valid and
reliable tools for assessing HRQOL in patients with dys-
pepsia. These instruments are more responsive to change
in HRQOL in dyspeptic patients, especially following
therapy, and hence ideal for evaluating newer medical
therapies, etc.
However, disease-specific instruments for dyspepsia do
not allow for comparisons with patients with illnesses
other than dyspepsia and with healthy individuals in the
general population. Generic HRQOL instruments are
therefore valuable to supplement disease-specific instru-
ments to enable such comparisons. The Short Form 36
Health Survey (SF-36) is one of the most widely accepted
generic instruments for measuring HRQOL in many coun-
tries [6]. However, it is relatively long and may not be
appropriate for large population surveys involving direct
interview techniques. The EQ-5D is another generic
HRQOL instrument that has been shown to be valid and
reliable in the general population and various patient
groups [7-9]. It is brief, comprising of five questions and
a visual analogue scale, which makes it easy to use and
particularly attractive in large scale population surveys, for
surveys in the elderly and those with lower educational
levels. It has the additional advantage of allowing incor-
poration of HRQOL data into pharmacoeconomic analy-
ses.
To compare HRQOL of dyspeptic patients with those of
the general population, the generic instrument has to be
shown to be valid and reliable in dyspepsia first. To our
knowledge, the EQ-5D has not been validated for this
purpose before and we therefore aimed to examine this in
a group of Malaysian patients with dyspepsia attending
regular follow up at a tertiary institution.
Methods
Subjects
Ethical approval was obtained by the University Malaya
Medical Centre Ethics Committee prior to the commence-
ment of this study. Consecutive adult outpatients with
dyspepsia attending the Gastroenterology clinic of this
tertiary teaching institution were invited to participate in
the study. Most of these patients had functional or non-
ulcer dyspepsia (defined as dyspepsia with a normal or
minor endoscopic findings), with the remaining attend-
ing follow up for organic disease (endoscopic findings of
duodenal erosions, peptic ulcer disease and erosive
oesophagitis). Patients were interviewed by a trained
research assistant using HRQOL and disease severity
instruments validated for use in Malaysia (see below) in
English or Malay (depending on individual patient's lan-
guage proficiency). Additional information obtained
included period of medical consultation and socio-eco-
nomic-demographic status. Test-retest reliability of EQ-
5D was evaluated by administering the EQ-5D twice to
the same subjects, 2-weeks apart, and comparing the
scores obtained on these two occasions. The second inter-
view was conducted over the telephone by our trained
research assistant.
Instruments
The EQ-5D comprises five questions on mobility, self-
care, pain, usual activities and psychological status with
three possible answers for each item (1 = no problems, 2
= moderate problems, 3 = severe problems) [7]. An overall
utility score is calculated based on these domains, with a
range score from 0 (worse health scenario) to a maximum
of 1.0 (best health scenario). An additional visual ana-
logue scale (VAS, scale 0 – 100) is used to assess general
health status with 100 indicating the best health status.
Malaysian English and Malaysian Malay versions of the
EQ-5D were developed by the EuroQoL Group: 2005
(original developers) using their standard translation and
linguistic validation process [10] and have been validated
for use in Malaysia.
The SF-36 is an established generic HRQOL instrument
which comprises 36 questions and eight different sub-
scores: physical functioning, physical role limitations,
bodily pain, general health perceptions, vitality, social
functioning, emotional role limitations, mental health
and 2 composite scores – Physical Component (PCS) and
Mental Component Scores (MCS) scored on a 0 to 100
scale [11]. The maximum score of 100 indicates the best
possible health state. English and Malay versions have
previously been validated in Malaysia and shown to be a
reliable measure of general QOL health status [12].
The Short Form (SF) Nepean Dyspepsia Index is a disease-
specific HRQOL instrument for dyspepsia, comprising a
10-item questionnaire examining the influence of dyspep-
sia on five elements (sub-scales) of health in patients,
namely tension/anxiety, interference with daily activities,
disruption to regular eating/drinking,
towards/control over disease symptoms and interference
with work/study [13]. Each item is measured by a 5-point
Likert scale ranging from 0 (not at all or not applicable),
1 (a little), 2 (moderately), 3 (quite a lot) to 4 (extremely).
knowledge

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Individual items are subsequently computed to obtain a
score range from 0 (lowest HRQOL score) to 100 (highest
HRQOL score) as per the developers' original calculation
formula [5]. A total, overall SF-NDI score is obtained by
the summation of all sub-scale scores followed by divi-
sion of five. This instrument has previously been shown to
be valid, sensitive and reliable for measuring HRQOL sta-
tus in Malaysian patients with dyspepsia [14]
The Leeds Dyspepsia Questionnaire (LDQ), is an eight item
symptom-based questionnaire relating to the frequency
and severity of various upper G.I. symptoms, namely
upper abdominal pain/discomfort, heartburn, regurgita-
tion, dysphagia, belching, nausea, vomiting and post-
prandial distension/early satiety [15]. The total score
ranges from 0 – 40, with lower values indicating less sever-
ity and higher values more severe dyspepsia. A score of 15
or more had been defined by the developers as indicative
of severe dyspepsia. The questionnaire has previously
been validated in our local population and shown to be
reliable in assessing dyspepsia amongst Malaysians [16].
Psychometric evaluation
Psychometric properties of the EQ-5D were evaluated by
assessing its frequency of missing data, ceiling and floor
effects (i.e. percentage of samples achieving highest and
lowest values), test-retest reliability and construct validity.
The reliability of an instrument refers to its ability to yield
reproducible and consistent results. Construct validity is
an assessment of the degree to which an instrument meas-
ures the construct that it was designed to measure. The
process involves forming hypothetical models to describe
the constructs being assessed and postulating their rela-
tionship. An assessment of the relationship between the
construct data is then made to confirm or refute prior
expectations and hence determine the validity of the
instrument being tested [17].
Construct validity of the EQ-5D was assessed by testing 26
a-priori hypotheses related to item or utility scores as fol-
lows: a) patients with less favourable demography in rela-
tion to dyspepsia would report more problems with
relevant EQ-5D dimensions, b) patients with more severe
dyspeptic symptoms would have more problems with rel-
evant EQ-5D dimensions and lower utility scores c) sub-
jects reporting problems for any EQ-5D dimensions
would have lower scores for relevant SF-36 and SF-NDI
scales and d) utility scores for EQ-5D would correlate well
with SF-36 and SF-NDI summary scores. Test-retest relia-
bility of EQ-5D was evaluated by administering the EQ-
5D twice to the same subjects, 2-weeks apart, and compar-
ing the scores obtained on these two occasions. The first
interview was conducted face-to-face and the second
interview was conducted over the telephone, both by our
trained research assistant.
Statistics
Hypothesized trends were tested using Chi-square or
Mann-Whitney tests, or Spearmans' correlation coefficient
where appropriate. Strong, moderate and weak correla-
tions were defined as > 0.60, 0.30 – 0.60 and < 0.30
respectively [18]. Test-retest reliability of the EQ-5D utility
score was assessed using intraclass correlation coefficients,
with a desired value of > 0.6 [17]. Statistical significance
for hypothesis fulfillment was defined as a p value of <
0.05. Data were analysed with SPSS for windows (version
12, SPSS Inc, IL, USA).
Results
Patient characteristics
A total of 113 consecutive patients with dyspepsia were
interviewed between May and October 2006 and their
characteristics and basic demography are summarized in
Table 1. The mean age of patients was 53.7 ± 14 years, the
male:female ratio was 1:1.02 and their ethnicity were as
follows: 28 (24.8%) Malays, 42 (37.2%) Chinese and 41
(36.3%) Indians. 90.3% of patients had above secondary
level education and most patients (41.6%) were retired at
the time of interview. The majority of cases (70.8%) were
functional dyspepsia and the median period of medical
consultation (either primary care or hospital specialist)
was 6 years (range 3 – 18). The median LDQ score in
patients was 16 (11 – 22), indicating that most patients
had fairly severe or poorly-controlled symptoms despite
many years of treatment.
EQ-5D data
The response rate was 100% with no missing data for all
variables. The calculated utility score had a median value
of 0.725 (skewness – 1.78), with a range from as low as
0.077 to a maximum of 1.00 (best health scenario). The
overall VAS had a median value of 70.0 (skewness – 0.52),
with a range from 20.0 to 95.0 (Figure 1).
Test-retest reliability
Ninety four (83.2%) patients participated in the follow-
up telephone interview, which was conducted at a median
of 16 days (range 13 – 18) after the original interview.
Intraclass correlation coefficient for the EQ-5D utility
score was 0.66 (95% CI = 0.55 – 0.76, p < 0.0001).
Validity
Twenty of the 26 hypotheses relating EQ-5D dimensions/
summary scores to other variables were fulfilled. At the
attribute level, problems with usual activity and pain were
associated with worsening dyspeptic symptoms but these
were not statistically significant. However, significantly
lower values for the EQ-5D utility scores and VAS were
demonstrated with severe dyspepsia (Table 2). All
hypotheses relating EQ-5D dimensions to relevant SF-36
sub-scales were supported (see Additional file 1). For

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example, patients who reported problems with mobility
in the EQ-5D had significantly lower scores in relevant SF-
36 sub-scales (i.e. physical functioning and role physical),
whilst those reporting problems with anxiety had signifi-
cantly lower scores for SF-36 mental health and role emo-
tional sub-scales (see Additional file 1). Five out of the 7
hypotheses relating EQ-5D dimensions to relevant SF-
NDI sub-scales were supported (see Additional file 1). In
particular, patients reporting problems with usual activi-
ties and pain demonstrated significantly lower scores in
the "interference" and "eating" sub-scales, whilst those
reporting problems with anxiety had significantly lower
scores in the "tension" sub-scales. Utility scores of the EQ-
5D demonstrated good correlation with the SF-36 physi-
cal component summary score (r = 0.45), the SF-36 men-
tal component summary score (r = 0.49) and the
cumulative SF-NDI score (r = 0.47) (see Additional file 1).
Discussion
The brevity and simplicity of the EQ-5D makes it particu-
larly attractive for use in large scale population surveys of
dyspepsia. Furthermore, a single utility score summariz-
ing all 5 dimension states in health can be used to calcu-
late quality-adjusted life years (QALYs) for cost-utility
analysis of interventions in dyspepsia, where most
patients have functional disease with variable outcomes.
However, before the EQ-5D can be utilized for dyspepsia
in this manner, it has to demonstrate satisfactory psycho-
metric properties in this condition. In this study of
Table 1: Characteristics and demography of Malaysian patients
with dyspepsia in the study
n = 113
Mean age (range)
53.7 ± 14 (17 – 83)
Gender (Male: Female)
1: 1.02
Ethnicity:
Malay
Chinese
Indian
28 (24.8%)
42 (37.2%)
41 (36.3%)
Education level:
Primary (6 years of education)
Secondary (12 years of education
Tertiary (at least 15 years of education)
11 (9.7%)
68 (60.2%)
34 (30.1%)
Marital status:
Unmarried/separate/divorced
Married
Widowed
21 (18.6%)
84 (74.3%)
8 (7.1%)
Employment status:
Employed
Unemployed/homemaker
Retired
42 (37.2%)
24 (21.2%)
47 (41.6%)
Diagnosis:
Functional dyspepsia
Peptic ulcer disease
Gastroesophageal reflux disease
80 (70.8%)
6 (5.3%)
27 (23.9%)
Length of dyspeptic symptoms (years)
(median; interquartile range)
7.5 (3 – 20)
Period of medical consultation (years)
(median; interquartile range)
6 (3 – 18)
LDQ score (median; interquartile range)
16 (11 – 22)
Histogram demonstrating range and distribution of EQ-5D VAS scores
Figure 1
Histogram demonstrating range and distribution of
EQ-5D VAS scores.
Table 2: Relationship of EQ-5D dimensions, utility scores and
VAS to other relevant variables
EQ-5D dimension/utility score vs variablen (%)p
Usual activity vs severe dyspepsia #
No problems
Got problems
45 (72.6%)
17 (27.4%)
0.07
Pain vs severe dyspepsia #
No pain
Moderate/extreme pain
10 (16.7%)
50 (83.3%)
0.06
Utility score vs dyspepsia#
Mild
Severe
0.78 *
0.72
0.002
VAS scale vs dyspepsia
Mild
Severe
60*
70
0.002
* median value
# Defined by LDQ – Mild < 15, Severe ≥ 15

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patients with dyspepsia from a variety of causes, from dif-
ferent ethnic backgrounds, of varying ages (from 17 – 83
years) and with > 90% secondary education, the EQ-5D
was found to be reliable and to have acceptable construct
validity, suggesting that it could be a useful generic
HRQOL measure for patients with dyspepsia.
Reliability assessment of a HRQOL instrument consists of
determining that a measurement yields consistent and
reproducible results [17]. We used the test-retest reliability
method in our population of stable dyspeptics and dem-
onstrated moderate to good reliability of the EQ-5D in
dyspeptics. Possible discrepancy with the follow-up inter-
view technique, as this was telephone based compared to
a face-to-face method at baseline may have resulted in a
lower intraclass correlation coefficient value. It was
unlikely that any major change in dyspeptic symptoms
could have occurred in the interval of (median) 2 weeks
between interviews as most patients had a prolonged
duration of symptoms (median 7.5 years, range 3 – 20
years) and were on regular anti-dyspeptic therapy.
The validity of the EQ-5D was demonstrated by the fulfill-
ment of twenty of the 26 hypotheses based on known-
groups construct validity. Hypothesized relationships for
the remaining six hypotheses were present, but failed to
reach statistical significance. For dyspepsia in particular,
the total utility score and the dimension of "pain" were
able to demonstrate poorer HRQOL outcomes in patients
with more severe symptoms. As the EQ-5D derives infor-
mation for each dimension of HRQOL from only one
item, it is important that we demonstrate this to be suffi-
cient by comparing it against a more detailed and estab-
lished multi-dimension instrument. In this study, we
demonstrated that patients reporting problems in all five
dimensions of the EQ-5D had significantly lower scores in
relevant dimensions of the SF-36. Furthermore, the over-
all EQ-5D utility score showed good correlation with the
SF-36 physical and mental summary scores, further sub-
stantiating the validity of the EQ-5D.
A possible limitation of many generic HRQOL instru-
ments are that dimensions of health being measured tend
to be more physical or mobility-based. In this context,
published literature on the validity of the EQ-5D in spe-
cific diseases have mainly been shown for physically lim-
iting illnesses such as Parkinson's disease [8],
rheumatological conditions [9] and stroke [19]. In this
study, we compared EQ-5D dimensions to a dyspepsia-
specific HRQOL instrument, the SF-NDI, and found that
physical dimensions dealing with "mobility" and "self-
care" had poor (i.e. non-significant or non-hypothesized
trend) associations and were not relevant to dyspepsia-
related HRQOL. This is not surprising at all as dyspepsia
rarely, if ever, causes problems with mobility and inability
to self-care. However, dyspepsia is known to be associated
with psychological disorders and can result in work-
absenteeism [20]. Accordingly, we demonstrated that
patients reporting problems in dimensions of the EQ-5D
relating to "usual activities" and "anxiety/depression" had
significantly lower scores in relevant SF-NDI sub-scales.
Additionally, those reporting problems with "pain/dis-
comfort" had lower scores with most SF-NDI sub-scales
(abdominal pain or discomfort being a predominant
symptom in dyspepsia) and the utility score correlated
well with the SF-NDI summary score.
A limitation of this cross-sectional study was the inability
to assess other properties of the EQ-5D in relation to dys-
pepsia, such as its' responsiveness. The latter requires a
cohort study to examine the ability of an instrument to
detect change in HRQOL status.
Conclusion
We are able to conclude that the EQ-5D is an acceptable,
valid and reliable generic instrument for measuring
health-related HRQOL in adult patients with dyspepsia.
Our data are consistent with other studies exploring the
validity of the EQ-5D in various disease states [8,9,19],
although most of these have been either neurological or
rheumatological conditions. We believe that the EQ-5D
may be useful in measuring health-related HRQOL in
other gastroenterological diseases, although further vali-
dation studies will have to be conducted to determine
this.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
SM and HLW designed the study, analysed and inter-
preted the data, and drafted the manuscript. KLG pro-
vided administrative support and contributed to data
collection with SM. JT provided technical support and crit-
ical revision of the manuscript. All authors reviewed and
approved final version of the manuscript.
Additional material
Additional file 1
Median scores and correlations of SF-36 (generic) and SF-NDI (dis-
ease-specific) dimensions with those of various EQ-5D domains. The
data provided represents correlation analysis between HRQOL domains of
the SF-36 and SF-NDI against the EQ-5D domains, whereby similarities
in relevant domains of HRQOL are highlighted.
Click here for file
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Acknowledgements
The authors wish to thank the EuroQol group for permitting the use of the
EQ-5D instrument for this study and for providing the locally validated lan-
guage versions of the instrument.
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