Rheumatology and Rehabilitation, 1976,15, 185
APPLICATION OF VISUAL-ANALOGUE SCALES
TO THE MEASUREMENT OF FUNCTIONAL
CAPACITY
E. C. HUSKISSON, JENNY JONES AND P. JANE SCOTT
St. Bartholomew's Hospital, London EC1A 7BE
VisiML-analogue scales have proved to be useful for the measurement of various
subjective states including pain, and their properties are now well documented (Huskisson,
1974; Scott and Huskisson, 1976). Their particular advantage over descriptive scales
is increased sensitivity. Though objective measurement of functional capacity or disability
is highly desirable, these states have a large subjective element. This study is a preliminary
attempt to use visual analogue scales to measure function and to test the value of such
a measurement. We chose to use functional measurements in a clinical trial situation
in which a clear difference between groups of patients with rheumatoid arthritis could
be predicted—one group received D-penicillamine and the other anti-inflammatory
therapy only.
METHODS
Twenty-two patients with rheumatoid arthritis completed six months' treatment;
11 received D-penicillamine in addition to routine anti-inflammatory therapy and 11
received anti-inflammatory therapy only. All had active disease of at least six months'
duration and were selected for this type of therapy because of persistently active or
progressive arthritis.
Two functions were chosen for assessment, tying a shoelace and writing an address
on an envelope. They were assessed in three ways, using a visual-analogue scale a simple
descriptive scale (couldn't, could with problem, slight dexterity problem, and no problem)
and recording the time taken to complete the manoeuvre. A visual-analogue pain scale
was also used. Assessments were made before the start of the study and again after six
months by a blind observer who was unaware of the treatment given and with whom
side-effects were not discussed.
The differences between initial and final measurements of pain and function were
analysed using Student's 7 ' test both between the groups and within each group.
Correlations were sought between different measures of function and pain, using the
Spearman ranking method.
RESULTS
Changes in pain and functional assessments are shown in Table I. As expected,
there was a statistically significant reduction in pain scores in the D-penicillamine185
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SUMMARY
Visual-analogue scales can be used to measure the subjective aspect of functional ability but,
in a group of patients with severe rheumatoid arthritis, the severity of impairment of two
predetermined functional tests was low in comparison with the severity of pain.
Measurements of the ability to carry out these two functions, using visual-analogue and
descriptive scales, and also using the time taken to perform the tasks, were not useful measures
of the effectiveness of treatment of rheumatoid arthritis.
Poor correlations were obtained between different measures of the same function and
between different functions measured in the same way.
186
RHEUMATOLOGY AND REHABILITATION VOL. XV NO. 3
TABLE I
CHANGES IN PAIN AND FUNCTIONAL ASSESSMENTS IN PATIENTS ON PENICTLLAMTNE OR ANTIINFLAMMATORY THERAPY ONLY
Function
PenicilJamine
Anti-inflammatory
6.9
0.2
0-2
0.2
0.5
1.2
SDSt
(4-point scale)
Time
(seconds)
(L)
(S)
(L)
(S)
0.5
0.1
0.2
0.1
11.9
10.0
5.1
4.6
There was a statistically significant difference between the groups only in terms of pain
scores.
• Visual-analogue scale,
t Simple descriptive scale.
L = letter; S = shoes.
treated group and a statistically significant difference in favour of this group compared
with patients on anti-inflammatory therapy only. In contrast, few of the functional
measurements showed a significant reduction within the groups and the difference in
pain relief between the groups was not reflected in the changes in functional measurements. Time taken to complete the functions improved to approximately the same
extent in both groups. Rating scales failed to improve in either group.
Correlation coefficients for the different measures are shown in Table n . Statistically
significant correlations were found only between the visual-analogue and descriptive
scales.
TABLE H
TABLE m
CORRELATION COEFFICIENTS FOR DIFFERENT METHODS
OF MEASURING FUNCTIONAL CAPACITY
CORRELATION COEFFICIENTS FOR
THE Two DIFFERENT FUNCTIONS,
MEASURED IN THE SAME WAY
Correlation Coefficients
Measurements VAS and SDS
Time and SDS
VAS and Time
Letter
Shoes
0.42*
0 35
0 31
054*
0.29
0.29
Measure
Ri
VAS
SDS
Time
025
0.23
0.42*
*P<0.05.
•P<0.05.
Correlation coefficients for the different functions tested are shown in Table III.
Only time taken to complete the function showed a significant correlation.
The distribution of one of the functional measurements on a visual-analogue scale
and the distribution of pain measurements, also on a visual-analogue scale, are shown
in Fig. 1. Whereas the distribution of pain measurements is uniform, functional measurements are clustered around the lower end of the scale. There was no significant correlation
between the severity of pain and functional impairment, both measured on a visualanalogue scale before the treatment (rg=O. 15, P>0.1).
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VAS •
Pain
(20-point scale)
(20-point •
scale)
(L)
(S)
SYMPOSIUM ON MEASUREMENT IN REHABILITATION
187
NO. OF
OISERVATIONS
14
12
10
t
COULDN'T
FUNCTION ( SHOES )
NONE
SEVERE
PAIN
FIG. 1.—Distribution of results of measurement of pain and function before the start of
treatment.
DISCUSSION
Visual-analogue scales were used in this study to measure function. They offer a
method of measuring the subjective aspect of disability which may have the advantage
of greater sensitivity than existing methods. However, in this experiment, functional
measurement was clearly a less useful indicator of improvement than measurement of
pain. One reason for this was presumably the greater severity of pain than disability.
The patients all had severe disease but may not have had difficulty with the particular
functions chosen for this study. Further studies will explore the value of measurement
of a function chosen as a particular problem by individual patients.
The time taken to complete the functions was not a useful measurement; it improved
in both groups of patients and correlated poorly with other measurements of the same
function.
REFERENCES
HUSKISSON, E. C. (1974) "Measurement of Pain". Lancet ii, 1127.
SCOTT, P. J. and HUSKISSON, E. C. (1976) "Graphic Representation of Pain". Pain 2, 175.
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COULD