British Journal of Rheumatology 1997;36:786–793
MEASUREMENT OF THE QUALITY OF LIFE IN RHEUMATIC DISORDERS
USING THE EUROQOL
F. WOLFE*‡ and D. J. HAWLEY†
*Arthritis Research and Clinical Center, †Wichita State University and ‡University of Kansas School of Medicine,
Wichita, KS, USA
SUMMARY
The EuroQol is a validated quality of life (QOL) scale that has been used in population and clinical studies, and has been reported
in patients with rheumatoid arthritis (RA). It is short, simple to complete, and might be suitable for surveys of rheumatic disease
patients. The properties of this instrument were investigated in a postal survey of 1372 rheumatic disease patients, including
537 with RA, 319 with osteoarthritis (OA) and 516 with fibromyalgia. In addition, simultaneous measurements of functional
disability, pain, psychological status, global severity and demographic characteristics were made. EuroQol scores (0.57) were
significantly lower than VAS health state scores (0.67) and arthritis-related global severity scores (0.62). QOL was similar in
RA and OA, but lower in fibromyalgia, across all instruments. The distribution of EuroQol scores had many gaps and was not
continuous. EuroQol did not reflect VAS QOL scores at EuroQol levels below 0.5, and the mean score difference between the
instruments below that level was 0.43. Many patients with low EuroQol scores (including some with health states that were ‘worse
than death’) had high VAS scores. These differences appear to have arisen because disability, pain and depression questions
ask about mild or moderate problems, but not both, thereby forcing scale compression in the mid ranges. In addition, the ‘severe’
value is so extremely abnormal that few patients endorse it. Finally, penalty scores are applied to those with at least one
maximally abnormal score. The scoring properties and distributional aspects of the EuroQol indicate substantial problems in
its use in rheumatic disease patients.
K : EuroQol, Quality of life, Rheumatoid arthritis, Osteoarthritis, Fibromyalgia.
T EuroQol is a validated, quality of life (QOL) scale
which identifies 243 possible health states based on five
questions concerning mobility, self-care, usual activity,
pain/discomfort, and anxiety/depression, with each
item having three possible levels (1, 2, 3) [1–9].
‘Utilities’ or societal valuations have been placed on
each state through a sample of 3235 persons, using time
trade-off to determine valuations [10]. Perfect health
and death have utilities of 1 and 0, and states worse
than death (Q0) are possible. Because it is short, the
EuroQol can be particularly useful in surveys. Such an
instrument would be valuable in following the course
and consequences of chronic rheumatic disorders. A
previous report suggested that the EuroQol might be
useful in assessing patients with rheumatoid arthritis
(RA) [4]. In the current study, undertaken to
investigate QOL in rheumatic disease (RD) and to
investigate the properties of the EuroQol, the EuroQol
was administered to 1372 patients: RA = 537, osteoarthritis (OA) = 319 and fibromyalgia (FIB) = 516.
their RD problem every 6 months. Beginning in 1981,
all new and returning patients attending the clinic were
systematically invited to participate in postal surveys.
At the time of the current survey (June 1994), 060%
of patients were participating in the postal survey
aspect of the study, although others participated
through telephone interviews or while attending clinic.
In general, patients participating in the postal survey
differ slightly from non-participants by virtue of having
more education, less pain, less Health Assessment
Questionnaire (HAQ) disability and better psychological status [11, 12]. The current report involves 1372
patients who completed a survey questionnaire for the
6 month period beginning June 1994. Five hundred and
thirty-seven had RA, 319 had OA and 516 had FIB.
Patients with RA met established criteria for diagnosis
[13, 14]. Osteoarthritis patients were diagnosed
clinically as having OA of the knee, hip or hand, and
the group was studied as a whole. Radiographic OA
was not a sufficient condition for diagnosis, although
it was a necessary condition. Diagnosis required pain
or dysfunction at the peripheral joint and radiographic
abnormality. Patients satisfied current American
College of Rheumatology criteria for diagnosis [15–17].
Patients with FIB had met current or previous
published criteria at the time of diagnosis [18]. Overlaps
in diagnosis were resolved as follows. RA patients were
classified as having RA regardless of any other RD
diagnosis; OA patients were classified as OA provided
only that they did not have an inflammatory rheumatic
disorder; FIB patients did not have diagnosed RA or
peripheral joint OA.
METHODS
The study population consisted of RD patients who
had attended an out-patient rheumatology clinic
(Arthritis Center, Wichita, KS, USA) and who had
agreed to participate in a long-term outcome study
which involved completing questionnaires regarding
Submitted 10 October 1996; revised version accepted 13 January
1997.
Correspondence to: F. Wolfe, Arthritis Research Center, 1035 N.
Emporia, Suite 230, Wichita, KS 67214, USA.
= 1997 British Society for Rheumatology
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WOLFE AND HAWLEY: EUROQOL IN RHEUMATIC DISORDERS
Demographic variables are captured using a method
of data capture and entry described by Wolfe et al. [19].
Briefly, by detailed self-report questionnaire and
interview, we question patients about all changes in
demographic status at each clinic visit and at each
questionnaire survey. The CLINHAQ is included in the
postal survey [19]. This instrument contains self-reports
for the HAQ disability index [20, 21], Arthritis Impact
Measurement Scales (AIMS) anxiety and depression
index [22], VAS pain, VAS global severity, VAS GI
symptoms, VAS sleep problems, VAS fatigue, satisfaction with health, patient estimate of health status, and
work ability. In the mailing of July 1994, we also
included the EuroQol questionnaire [7, 9].
The specific pain assessment used a double-anchored
VAS scale labelled on one end, ‘No Pain’ and on the
other end, ‘Severe Pain’. The question read ‘How much
pain have you had because of your illness in the past
week?’ The range of the scale is 0–3. The specific
questions and anchors for the global severity scale
read: ‘Consider all of the ways that your illness affects
you, rate how you are doing by placing a mark on the
line’ (Very Well, Very Poor).
The EuroQol consists of five domains of three
statements each. Patients were asked to tick one
statement for each domain. The domains and
statements were as follows.
Mobility. (1) I have no problems walking about; (2)
I have some problems walking about; (3) I am confined
to bed.
Self-care. (1) I have no problems with self-care; (2)
I have some problems washing or dressing myself; (3)
I am unable to wash and dress myself.
Usual activities. (1) I have no problems performing
my usual activities (e.g. work, study, housework, family
or leisure activities); (2) I have some problems with
performing my usual activities; (3) I am unable to
perform my usual activities.
Pain/discomfort. (1) I have no pain or discomfort; (2)
I have moderate pain or discomfort; (3) I have extreme
pain or discomfort.
Anxiety/depression. (1) I am not anxious or
depressed; (2) I am moderately anxious or depressed;
(3) I am extremely anxious or depressed. ‘Utilities’ or
societal valuations are then placed on each state based
on a sample of 3235 persons, using time trade-off to
determine valuations [10]. Perfect health and death
have utilities of 1 and 0, and states worse than death
(Q0) are possible.
The EuroQol VAS is a single vertical ‘feeling
thermometer’ asking people to rate their health
between the ‘best imaginable health state’ and the
‘worst imaginable health state’. It is scored between 0
and 100, but has been rescaled here to 0–1 for
comparison with the EuroQol. The instructions ask
participants to consider ‘all aspects of your health not
just your arthritis or muscle problem’. The global
severity scale, on the other hand, restricts the question
to ‘all the ways that your illness affects you’. The global
severity scale has also been rescaled to 0–1 and reversed
to be compatible with the EuroQol. The EuroQol
represents the calculated utility as determined from the
published tariffs [10]. In Table I, we also present the
HAQ disability, VAS pain and the anxiety and
depression scales of the AIMS. Except for the EuroQol
and the anxiety and depression scales, the other scales
in this table have been reversed and rescaled to a
minimum of 0 and a maximum of 1, for ease of
comparison. In all cases, 1 represents the perfect health
condition and 0 represents the worst health condition.
TABLE I
Mean scores and correlations for EuroQol, VAS Health State, VAS Global Severity, HAQ DI, VAS Pain and AIMS Anxiety and Depression
RA
OA
Fibromyalgia
All groups
N
EuroQol
EuroQol VAS
Global Severity
537
0.57 (0.25)
0.67 (0.19)
0.62 (0.24)
319
0.56 (0.25)
0.68 (0.19)
0.60 (0.23)
516
0.45 (0.31)
0.58 (0.21)
0.50 (0.25)
1372
0.53 (0.28)
0.63 (0.20)
0.57 (0.25)
HAQ DI
Correlation
Correlation
Correlation
Pain
Correlation
Correlation
Correlation
Depression
Correlation
Correlation
Correlation
Anxiety
Correlation
Correlation
Correlation
0.60 (0.26)
0.696
0.475
0.622
0.61 (0.25)
0.643
0.552
0.781
2.15 (1.59)
−0.546
−0.493
−0.451
3.25 (1.91)
−0.477
−0.477
−0.399
0.65 (0.23)
0.645
0.500
0.595
0.55 (0.26)
0.567
0.397
0.699
2.26 (1.67)
−0.496
−0.499
−0.486
3.30 (1.84)
−0.431
−0.433
−0.422
0.64 (0.24)
0.703
0.518
0.598
0.44 (0.25)
0.644
0.523
0.726
3.26 (1.96)
−0.547
−0.515
−0.505
4.78 (2.04)
−0.472
−0.457
−0.418
0.62 (0.25)
0.671
0.474
0.574
0.53 (0.26)
0.625
0.524
0.746
2.60 (1.83)
−0.546
−0.521
−0.511
3.04 (2.08)
−0.482
−0.482
−0.448
with EuroQol
with EuroQol VAS
with Global Severity
with EuroQol
with EuroQol VAS
with Global Severity
with EuroQol
with EuroQol VAS
with Global Severity
with EuroQol
with EuroQol VAS
with Global Severity
For comparison with the EuroQol in which 0 represents death and 1 is perfect health, we rescaled EuroQol VAS, Global Severity, HAQ
Disability and Pain to a 0–1 scale, reversing the scales when necessary so that 0 was the worst score and 1 the best score. Anxiety and depression
are in original units.
Correlations are Spearman. Numbers in parentheses represent the standard deviation.
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BRITISH JOURNAL OF RHEUMATOLOGY VOL. 36 NO. 7
F. 1.—Distribution of EuroQol scores. Values to the left of the vertical line at 0 indicate states ‘worse than death’.
Statistical analyses
Data were analysed using Intercooled Stata version
5.0 for Windows (23). Correlations were Spearman.
Group differences were tested by t-tests or x 2 tests, as
indicated. Augmented component plus residual plots
were performed according to the method of Mallows
[24]. A small amount of spherical random noise has
been added to Figs 2–4 to aid in seeing overlapping
points. Statistical significance was set at 0.05. All tests
were two-tailed.
RESULTS
Demographics
Patients with three rheumatic disorders were studied:
RA (N = 537), OA (N = 319) and FIB (N = 516). In
all, there were 1372 patients. The mean age of the
group was 61.1 (.. 13.8) and 83.1% were women.
Differences between three measures of QOL
Table I presents three measures of QOL or health
status: the EuroQol, the EuroQol VAS and a global
severity scale. The EuroQol is correlated with EuroQol
VAS at 0.568 and with global severity VAS at 0.602.
The two VAS scales are correlated at 0.616. For all
groups considered, ‘overall health’ as rated by EuroQol
VAS is better than ‘arthritis health’ as rated by global
severity (P Q 0.001). In turn, EuroQol health, as
determined by the questionnaire and published tariffs,
is worse than indicated by either of the other two
measures (P Q 0.001). These differences are constant
across all of the diagnostic groups. EuroQol and
EuroQol VAS both identify RA and OA patients as
being similar in QOL, but find FIB patients to have
lower scores for both measures. These results are in
accord with HAQ disability, pain, anxiety and
depression scores. Both the EuroQol and the EuroQol
VAS are significantly correlated with the other
measures but, except for anxiety, the correlations are
always stronger with EuroQol then with EuroQol VAS,
and stronger still with the global severity scales. This
may be expected since the EuroQol is composed of
measures of function, pain and anxiety/depression, and
the global scale directly reflects arthritis severity, while
the VAS scale reflects only the global dimension of
health. In the analyses that follow, the diagnostic
groups were combined and analyses are for the entire
group.
Problems with EuroQol scores and scaling
To attempt to understand the discrepancy between
the two EuroQol scales, the scales were graphed (Figs 1
and 2). Four problems were identified. First, the
distribution of EuroQol scores has many gaps, and it
is particularly sparse between 0.25 and 0.5 (Fig. 1). In
fact, there would seem to be two large groupings (or
distributions): those between 0.5 and 0.75, and those
between −0.25 and 0.25. Specifically, 75.9% of all
patients are distributed in 21 health states between 0.5
and 0.883. Second, the scatter of the EuroQol VAS is
quite great at some EuroQol health states, e.g. at 0.5
and 0.0 (Fig. 2). Third, there are many patients with
EuroQol health states less than 0 (‘worse than death’)
(Figs 1 and 2) and, finally, in many instances there is
great discrepancy between the two measures for a
WOLFE AND HAWLEY: EUROQOL IN RHEUMATIC DISORDERS
number of patients (Fig. 2). The obvious examples are
those patients with EuroQol scores from −0.25 to 0.25
who have VAS scores above 0.5.
To study the effect of these differences (Fig. 3),
patients were divided into three groups according to
EuroQol scores: −0.05 to 0 (group 1), 0.02–0.49
(group 2) and 0.5–1 (group 3). In group 3, the
difference between EuroQol scores and the VAS
estimate of health state was 0.02, but in groups 1 and
2, the difference was 0.45 and 0.41, respectively. All
differences were significant at Q0.001. That is, at levels
of the EuroQol below 0.5, the two tests are in
substantial and striking disagreement, with EuroQol
being, on average, 0.43 lower than the result obtained
with the VAS scale.
To understand the discrepancies between the
EuroQol scores based on tariffs and the VAS score,
we examined the individual EuroQol components
and compared them with clinical scales of the
HAQ disability index, VAS pain and the AIMS
depression scale. As shown in Table IIa, the EuroQol
has four categories, two at the extreme ends and two
in the middle, one of which is used in each scale.
Table IIb breaks up the clinical variables into similar
groups.
For mobility (Table IIa), it can be seen that that
almost no patients are in category IV (‘confined to
bed’), and that 70.2% have some problems. This would
seem to be an inadequate distribution of groups when
compared to data from the HAQ (Table IIb) where
789
42.6% have moderate problems and 11.3% have severe
problems. For self-care and usual activities, the
category IV description is ‘unable’. For the EuroQol
categories, 99.3% have no or some problem with
self-care and 95% have no or some problem with usual
activities, but these numbers fall to 46.1% for the
HAQ.
Similar problems are found with pain. The EuroQol
finds 78.6% with moderate pain, but there is not a
category for mild pain. Using a VAS pain score
between 1 and 2 on the 0–3 point VAS scale, a
markedly different distribution of pain scores is seen,
with only 36.6% in the moderate category. For
depression, an AIMS depression score of 4 is associated
with probable clinical depression, and scores between
3 and 4 with important depressive symptoms. Once
again there are substantial differences in the distribution of scores for the two tests, with more severely
depressed patients being found in the AIMS category
groups.
To test whether the scaling used by the EuroQol,
compared with the non-restricted scaling of the VAS
scale, resulted in practical differences, two regression
analyses were performed. EuroQol, then EuroQol
VAS, was regressed on HAQ disability, pain and
depression. Next, augmented component vs residual
plots were examined (Fig. 4a and b). In all instances,
an excellent fit was found with the VAS scale, but a
poor fit was found with the EuroQol scale. As shown
in Fig. 4a, residuals are significantly above the fit
F. 2.—Plot of visual analogue health states vs EuroQol health utilities based on published tariffs. Values to the left of the vertical line at 0
indicate states ‘worse than death’. The regression line is locally weighted regression (Lowess) using a bandwidth of 0.4. The Pearson correlation
coefficient is 0.568.
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BRITISH JOURNAL OF RHEUMATOLOGY VOL. 36 NO. 7
F. 3.—Graph of the difference of VAS-EuroQol vs EuroQol score. There is substantial disagreement between the score at EuroQol levels less
than 0.5. The curved line is a cubic spline fit through the data points.
regression line when pain scores are between 1 and 2,
and below the line when they are above 2.
DISCUSSION
The EuroQol has been used as a survey instrument
in populations [1, 7, 8] as well as in patient care settings
TABLE IIa
Proportion of patients with differing levels of problem for EuroQol
categories
Component
Mobility
Self-care
Usual activities
Pain/discomfort
Anxiety/depression
IV
Unable,
extreme pain
I
II
III
or
No
Some
Moderate psychological
problem problems problem
distress
29.4%
57.3%
21.0%
3.7%
45.1%
70.2%
42.1%
74.0%
78.6%
50.1%
0.4%
0.7%
5.0%
17.7%
4.7%
TABLE IIb
Proportion of patients with differing levels of problem for HAQ
Disability, Pain and Depression
Component
HAQ DI*
Pain*
Depression†
I
II
III
No
Some
Moderate
problem problems problem
18.0%
28.1%
8.4%
31.2%
67.0%
42.6%
36.4%
15.1%
*HAQ and pain scores divided at 0.25, 1, 2.
†AIMS depression divided at 3, 4 [22].
IV
Severe
problem
11.3%
24.1%
17.6%
[2–5, 25–27]. Using the EuroQol utilities, one can
determine differences in severity between illnesses and
also measure changes within illnesses in response to
treatment. It is part of the design of the instrument that
it must capture the best and worst possible health state
for each item [1]. It is also recognized that the EuroQol
should be used along with a disease-specific healthrelated QOL measure [1]. This latter recommendation
reflects the relative insensitivity to change that generic
QOL measures and the EuroQol have compared to
specific measures [7]. In spite of the recommendation
that a disease-specific instrument also be used, the
EuroQol must be able to reflect accurately the range
and distribution of health states within an illness to be
valid. The results of the current study suggest that the
EuroQol may not fulfil this requirement in RD
patients.
The scaling of the individual EuroQol questions
seems inappropriate and too narrow to capture many
important RD changes. For mobility, the two extreme
categories are ‘no problem’ and ‘confined to bed’, and
for the self-care and usual activities there is similar
extreme scaling. Since almost no patients will be in the
‘unable’ category, the only movement that can be
detected will be between ‘no problems’ and the
presence of ‘problems’. It is apparent, therefore, that
the EuroQol cannot reflect changes in functional status
that do not involve movement to and from category I
to categories II–III. Tables IIa and IIb also suggest
that pain is not adequately categorized, since almost
80% are in category III. One can easily imagine a
WOLFE AND HAWLEY: EUROQOL IN RHEUMATIC DISORDERS
791
(a)
(b)
F. 4.—(a) and (b) Augmented component plus residual plots for the regression of EuroQol and EuroQol VAS on Pain, HAQ Disability and
Depression. The curved line is a cubic spline fit through the data points. The solid line is the predicted regression line. (b) shows that the regression
line fits the data well for the VAS scale, but (a) (EuroQol) shows a poor fit, with residuals above the line when pain scores are between 1 and
2, and below the line when scores are above 2.
patient with active RA who has a successful total joint
arthroplasty which improves pain, function, and
anxiety and depression, yet who has no change in the
EuroQol score.
Scaling problems, i.e. inadequate range of choices
within each item, are among the factors that lead to the
problems in distribution of scores and disagreement
between the EuroQol and VAS measures that are seen
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BRITISH JOURNAL OF RHEUMATOLOGY VOL. 36 NO. 7
in Figs 1–3. At a clinical level, there is only slight
disagreement between the EuroQol and the VAS scores
for values of 0.5 and above (0.02), but there is marked
disagreement below that level, with an average
difference in scores of 0.43 (Fig. 3). One possible
explanation for the gap between 0.25 and 0.5 on the
EuroQol scales is that respondents who score in the
most abnormal category for any of the five items have
an additional 0.269 subtracted from their EuroQol
score by EuroQol scoring rules. To see if this might be
the full explanation, 0.269 was added to all EuroQol
scores below 0.5. Although this narrowed the gap, it
did not change the lack of agreement between EuroQol
and VAS below the 0.5 level. To understand further the
differences between the EuroQol and the VAS models,
EuroQol and the VAS scales were regressed on HAQ
disability, pain and depression in two separate models.
Augmented component vs residual plots for each of the
independent variables were then examined. These plots
showed non-linearity in the EuroQol model, but not
the VAS model, for the three independent variables
(Fig. 4a and b). This was particularly the case at the
intermediate and high levels of the variables. These
abnormalities appear to be the results of the scaling
rules used by the EuroQol. They suggest that, as a
measure of QOL in RD patients, the EuroQol does not
reflect clinical data accurately.
Among the limitations of our study is that the
utilities derived from European populations may not
hold for the USA. Even so, the disparity between the
EuroQol and the EuroQol VAS has been noted by
others [4]. One explanation for the mediocre correlation between the EuroQol VAS and the EuroQol
utilities (r = 0.568) may lie in the observation that the
utilities are derived from a generally healthy population, whilst the VAS scores are obtained from RA
patients. In addition, the EuroQol VAS, the ‘arthritis’
global severity scale, and EuroQol utility-based scales
might differ because the EuroQol VAS is a measure of
overall health, the global scale a measure of the
‘impact’ of arthritis or arthritis health, and the
EuroQol a measure of impairment and disability. Thus,
perhaps we should expect the three scales to yield up
somewhat different results. In that respect, as noted in
Table I, the global severity scale correlates better with
HAQ and pain than does the EuroQol VAS, but global
severity and EuroQol VAS do not differ in their
correlations with the psychological scales. These three
scales underscore the arbitrary nature of the term
‘quality of life’. Perhaps, instead, they are all measuring
different aspects of ‘health status’.
Although the EuroQol has been validated in
population surveys [1, 6, 7] and appears to perform well
there, its value in RD populations, based on our
results, remains uncertain. While it is certain that the
EuroQol can identify alterations in patients when
individual items change from mild or moderate to no
symptoms or extreme symptoms, it seems likely that it
will fail to identify lesser changes. If an instrument
cannot, then, identify major but not complete
therapeutic improvement, as manifested by improve-
ment in pain and function, then it cannot accurately
capture health states in illnesses such as RA. The
problems of the EuroQol—distribution of scores,
discordance with VAS at lower levels of the EuroQol,
and compression of item range—suggest a limited role
for this instrument in rheumatology at this time.
A
This study was supported in part by grants from the
National Institutes of Arthritis, Diabetes, Digestive,
and Kidney Diseases (AM21393) to the Arthritis,
Rheumatism, and Aging Medical Information System
(ARAMIS), Palo Alto, CA, USA.
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