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Measurement of functional status quality of life and utility in rheumatoid arthritis.

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59 1
REVIEW
MEASUREMENT OF FUNCTIONAL STATUS,
QUALITY OF LIFE, AND UTILITY
IN RHEUMATOID ARTHRITIS
MARY J. BELL, CLAIRE BOMBARDIER, and PETER TUGWELL
Rheumatoid arthritis (RA), a chronic inflammatory disease of unknown etiology, has no known cure,
and may run a protracted course. Traditional epidemiologic measures of disease outcome, such as death or
resolution of illness, reflect only the extremes of
outcomes of RA. Recognition of the impact of this
chronic disease on the individual has led to the development of quality of life instruments, which measure
more relevant health outcomes such as physical, mental, and social well-being and reflect the management
goals of preservation of function and limitation of
symptoms (1). In addition, these instruments track
changes in health status over time, prognostically
stratify patients, and assist in the targeting of interventions. More recently, utility measures have been used
to combine the risks and benefits of an intervention
into a single measure. We review here some representative instruments that have been used in assessments of patients with RA. The format of this review
will follow the clinical questions format outlined in
Table 1.
From the Department of Clinical Epidemiology and Biostatistics and the Department of Medicine, McMaster University,
Hamilton, Ontario; and the Department of Medicine and Health
Administration, University of Toronto, Toronto, Ontario, Canada.
Mary J. Bell, MD, FRCPC: Assistant Professor, Department of Clinical Epidemiology and Biostatistics and Department of
Medicine, McMaster University; Claire Bombardier, MD, FRCPC:
Associate Professor, Department of Medicine and Health Administration, University of Toronto; Peter Tugwell, MD, MSc, FRCPC:
Professor, Department of Clinical Epidemiology and Biostatistics
and Department of Medicine, McMaster University.
Address reprint requests to Mary J. Bell, MD, Suite 804,25
Charlton Avenue East, Hamilton, Ontario L8N 1Y2, Canada.
Submitted for publication December 28, 1988; accepted in
revised form October 23, 1989.
Arthritis and Rhenmatisrn, Vol. 33, No. 4 (April 1990)
Is the measurement of quality of life
something new?
Interest in the development of a functional
index began in the 1930s. The knowledge that physiologic improvements were not always reflected by
increased functional ability resulted in the creation of
a few simple functional scales, such as the American
Rheumatism Association (ARA) functional capacity
classification, the New Y ork Heart Association scale,
and the Karnovsky Index. These were designed primarily for broad application and rapid classification of
a patient population. Although they have been useful
in detecting a large magnitude of change in an individual patient, they have not been as useful in detecting
the small but clinically important improvements that
result from most therapeutic interventions used in
rheumatology .
Concern about quality of medical care in the
1960s led to a more comprehensive evaluation of the
impact of clinical services. Scales were devised that
incorporated longevity, symptoms, presence of physiologic abnormalities, functional status, psychosocial
factors, compliance, and satisfaction. Driven by the
need for program evaluation and policy making, wider
applicability of these measures was sought. “General
health status” instruments that could be used in community, general patient, and specific disease populations were developed.
Both clinical rehabilitation and health service
research in the 1980s further advanced the science of
quality of life and utility measurement. These tools
allow one to measure the end product of the health
care system as it concerns the patient. From this base,
BELL ET AL
Table 1. Clinician’s questions
Is the measurement of quality of life something new?
Why do I need to know about these measures?
What is available?
How could I use them?
How well do these instruments perform when their
measurement characteristics are tested?
6. How should I evaluate any new quality of life measure?
7. Is the state of the art sufficiently advanced that drug approval
agencies should require quality of life data before approval?
8. What will the future bring in the way of further development of
these measures?
1.
2.
3.
4.
5.
more comprehensive, disease-specific health status
and utility measures have been created (2).
W h y do I need to know about these
measures?
Functional status, quality of life, and utility
measures have developed out of a need to define to a
greater extent the effects of health care interventions
and the impact of disease on the individual as well as
groups of individuals with chronic disease. These
instruments have been shown to be conceptually relevant, reliable, valid, and as responsive to change as
traditional outcome measures. Prospective evaluation
of the patient population by use of these measures has
demonstrated that they may also have predictive value
for determining eventual outcome.
Sherrer et al studied a population of 75 RA
patients over a 12-year period (3). They noted that the
course of major disability in RA was established in the
first few years of disease. The best predictors of
disability included age, radiologic grade, sex, rheumatoid factor, nodules, and initial functional status.
When a cross-sectional population study was conducted, it appeared that a tetrad composed of high
early disability scores, female sex, older age, and
abnormal radiographic findings at clinical presentation
predicted the likelihood of developing significant disability (3).
More recently, Pincus et al reported the results
of a prospective study of morbidity and mortality in 75
RA patients in which quantitative measures of functional capacity were documented at baseline and 9
years later (4). There was >50% mortality at 5 years
among patients who had severe dysfunction at baseline, as measured by questionnaire, grip strength, and
modified walking time (time required to walk at a
normal pace for 25 feet). Such a prognosis is comparable with that of patients with cardiovascular diseases
and patients with malignant diseases. The higher relative risks associated with measures of poor functional
capacity could not be explained by demographic,
disease therapy, or comorbidity variables (4).
These findings are consistent with those of
Mitchell et al, who demonstrated that age and ARA
functional class were the 2 most important predictors
of mortality in the RA population (5). These studies
show that knowledge of the patient’s baseline functional status allow the clinician to identify those patients with a poor prognosis.
Thus, the information gathered using these instruments may provide clinically useful information
regarding current RA status, utilization of health care
services, and prediction of future outcome, such as
mortality, that are not readily available through conventional testing (3-7).
What is available?
There is no single quality of life instrument that
can be used to assess outcome in every situation. The
instrument of choice depends on the purpose for which
it will be used, the practicality of the instrument, and
the population being studied. Recently, a classification
scheme for health-related quality of life measures was
proposed by Guyatt et a1 (8). It was designed to
delineate the range of application and content of the
various measures. The 2 major categories of this
system are generic instruments and arthritis-specific
instruments.
Generic instruments. Generic instruments have
been developed to reflect the impact of ill health on the
lives of people in a wide variety of populations. They
cover function, disability, and distress. Subcategories
of the generic measures include health profiles, utility
measures, and single-item self-rating health scales (8).
As demonstrated in Tables 2 and 3, there are many
different tools within each class of instrument. Representative examples from each class are summarized
below.
Health profiles. Health profiles are single instruments that measure different aspects of quality of
life in a wide variety of conditions. A scoring system
permits aggregation of the collected information into a
score or index. Such instruments allow for assessment
of the effects of an intervention on many aspects of
quality of life through the use of only 1 instrument.
The primary disadvantage of this method of determining quality of life is its potential insensitivity to disease-specific, clinically important change (8). Com-
OUTCOME MEASUREMENT IN RA
Table 2.
593
Content of generic and arthritis-specific questionnaires*
Physical health
Instrument
Generic (health profiles)
MHIQ
Rand HIS
SIP
Arthritis-specific
AIMS
ARA FC
FSI
HAQ
Katz
Lee
MACTARPET
TQ
Social health
Mobility/
Leisure
physical Self- Role CommuniSocial
group Psychological
activity care activity
cation
interaction activity
health
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
t
+
+
+
+
+
+
o
+
+
+
+
0
+
+
+
+
+
0
+
+
+
+
+
+
+
0
0
+
0
0
0
0
0
0
+
+
0
0
0
0
0
+
O/ +
+
0
+
+
+
+
0
O/ +
+
+
0
* MHIQ = McMaster Health Index Questionnaire; + = property tested; Rand HIS = Rand Health
Insurance Study; 0 = property not tested; SIP = Sickness Impact Profile; AIMS = Arthritis Impact
Measurement Scales; ARA FC = American Rheumatism Association Functional Classification: FSI =
Functional Status Index; HAQ = Health Assessment Questionnaire; Katz = Katz's Activities of Daily
Living Instrument; Lee = Lee's Functional Status Instrument; MACTAWPET = McMaster-Toronto
Arthritis Patient Preference Disability Questionnaire/Problem Elicitation Technique; TQ = Toronto
Questionnaire.
monly used health profiles include the McMaster
Health Index Questionnaire (MHIQ), the Rand Health
Insurance Study (HIS), and the Sickness Impact Profile (SIP) (9-1 I ) .
The MHIQ is a SPitem, self-administered questionnaire that can be completed in 20 minutes. It
examines physical, social, and emotional function.
Function scores are standardized to index values
Table 3. Measurement characteristics of generic and arthritis-specific questionnaires*
Instrument
Generic
Health profiles
MHIQ
Rand HIS
SIP
Utility measures
IWB
PUMS
Rating scale
SG and rating
chart
?TO
WTP
Arthritis-specific
ACTRE
AIMS
AKA FC
FSI
HAQ
Katz
Lee
MACTAWPET
TQ
Reliability
Validity
+
-+
f
+
?
?
+
+
+
?
+
+
+
+
+
+
+
+
?
+
+
+
+
+
7
+
+
+
+
+
+
+
+
+
+
+
Mode of
administrdtion
Administration
time (minutes)
Interviewer
Self-report
Interviewer/self-report
20-40
Interviewer
Interviewer
Interviewer
Interviewer
?
30
10
30-60
Interviewer
Interviewer
30-60
?
Self-report
Self-report
Clinical judgement
Interviewer
Interviewer/self-report
Clinical self-report
Self-report
Interviewer
Interviewer
2a
Minimal
60-90
10
Short
Short
10-20
15-20
60
2&30
?
~~~
* IWB = Index of Well Being; ? = property unknown; PUMS = Patient Utility Measurement Set; SG
= standard gamble; TTO = time trade-off WTP = willingness to pay; ACTKE = National Institutes
of Health Activity Record. See Table 2 for other definitions.
BELL ET AL
ranging from 0.0 (extremely poor function) to 1.0
(extremely good function). Retest reliability for the
physical function score is 0.80 (12). MHIQ scores
correlate well with global assessments by health professionals (13-15) or by relatives or friends (15) and
with biologic parameters of disease severity (13,16).
The Rand HIS batteries provide a detailed
assessment of the following 4 areas: social function,
psychological function, physical function, and general
health perceptions. Completion of this intervieweradministered questionnaire requires 60 minutes. The
Arthritis Impact Measurement Scales (AIMS) anxiety
and depression scales evolved from the Rand HIS
psychological measures (10).
The SIP, a behavior-based measure of health
status, has been shown to be of use in the study of
people with arthritis (17). It was conceived as a
measure of functional performance of the individual
patient, but it came to be used as more of a health
assessment tool for measuring health levels in a population. It has been used primarily as a health survey
instrument, as well as an outcome measure for evaluating longitudinal treatment regimens and methods of
delivering service. The focus of the SIP is dysfunction.
Levels of positive function are not assessed. The SIP
assesses 12 categories, which include ambulation,
mobility, body care, movement, social interaction,
communication, alertness behavior, sleep and rest,
eating, work, home management, and recreation and
pastimes. The questionnaire consists of 136 items. is
self-administered. and takes 20 to 30 minutes to complete ( 1 1).
Utility instruments. Utility measures of healthrelated quality of life were derived from economic and
decision theories. They provide us with a quantitative
measure of the value or preference the patients attach
to their overall health status relative to perfect health
(score of 1 ) and death (score of 0). Accordingly,
changes in utility as a result of a specific intervention
reflect changes in the value of an individual's health
status, a key component in the evaluation of an
intervention's usefulness in RA. They therefore reflect
the trade-off between thc risks and benefits of an
intervention. The use of utility meawres allows for a
cost-utility analysis, which is advantageous to planners and policy makers. The acceptability, reliability,
and validity of this approach have been documented in
a range of disorders and patient groups. but to date,
these measures have been used only once among
patients participating in a placebo-controlled, randomized trial of auranofin (18-20).
There are 2 approaches to utility measurement.
The first approach is to classify patients into categories
based on their responses to a number of questions
about their function. The Quality of Well-Being
(QWR), also known as the Index of Well-Being (IWB),
and the Health Status Index (HSI) use this approach.
The QWB determines what the patient did or did not
do because of health reasons within 3 areas: mobility,
physical activity, and social activity. It places health,
disability, and death on a single scale. Each area has 4
or 5 levels of performance. Therefore, patients are
classified as belonging to 1 of 43 possible combinations
of levels. Each state of health has been valued using
preference measurement techniques obtained from the
activity profiles of normal individuals in the general
population. These weights have also been evaluated in
RA patients (21). The preference value is then assigned to each health state and modified by the presence or absence of a standard list of similarly valued
symptoms. The overall QWB places patients on a
utility scale that ranges from 0 (dead) to 1 (healthy).
This approach to the measurement of health status has
been used in a variety of conditions for health care
planning. The QWB has been demonstrated to be a
useful tool for measuring both the change in RA
patient status and the cost-utility of an intervention
such as total joint replacement (22). The QWB has also
influenced the design of other global scales such as the
Rand HIS and the disease-specific AIMS.
The second approach to utility measurement is
to ask patients to make a single rating of all aspects of
their quality of life. Some representative tools using
this approach include rating scales, the standard gamble (SG) method, time trade-off ('I'TO) techniques, and
willingness to pay (WTP) (18-20,23,24).
A rating scale consists of a line on a page with
clearly identified end points. The most preferred
health state is identified at one end and the less
preferred at the other. Remaining health states are
placed on a line between these 2 end points in order of
preference. The intervals between placements correspond to differences in preference as perceived by the
subject (18,19).
The SG method is a paired comparison in which
the subject must choose between 2 alternatives with
varying probabilities of occurrence (23).
The IT0 technique is valid only for health
states that are preferred to death. It is simpler than the
standard gamble. It is also a paired comparison in
which the subject must choose between 2 alternatives,
such as a shorter healthy life versus a longer chronic
OUTCOME MEASUREMENT IN RA
disease state. This instrument is based on the theory
that the less desirable the health state, the greater the
amount of life the subject will trade off in order to be
free of the undesirable health state. When the point of
indifference is found, the utility for the health state can
be calculated (18,19).
The WTP questionnaire has been used to evaluate health gains. Patients with RA have been asked
how much of their income they would pay and how
large a mortal risk they would accept to achieve a
hypothetical cure. In one study, the majority of patients were willing to pay 22% of their household
income for a cure (24).
Utility measures are potentially useful in rheumatology to help determine the acceptable risk of drug
treatment. Factors that determine if a risk is acceptable include the seriousness of the risk. the benefit that
the drug is expected to produce, and the available
alternative treatments.
Torrance has compared 3 techniques with regard to ease of use in arthritis patients (reliability,
criterion and construct validity, and cost), and has
suggested that the best instrument for use in these
patients is the rating scale, followed by the time
trade-off and the standard gamble (19). To date, the
only published drug trial using utility measures is the
auranofin multicenter trial of 1986 (20). The instruments used included the Patient Utility Measurement
Set (PUMS), standard gamble, and willingness to pay.
The PUMS is a detailed questionnaire administered by a trained interviewer. The patient is asked to
compare “full health” with his current state of health
and his recollected perception of his health state
pretrial. Components of the instrument present sacrifice or risk in a variety of terms. including percent
chance, months per year, and years of life. In the
auranofin trial, the PUMS performed better in detecting statistically significant differences between treatment groups than did the 2 simpler utility questionnaires. The PUMS was the only instrument of the 3
utility instruments used that took into account the
pretrial state. It was also the only preference instrument that had detailed and standardized instructions
and method of administration for the interviewer. This
may explain the difference in ability to demonstrate
statistically significant differences between treatment
groups. Further development and testing of these
instruments for use in clinical trials in the rheumatic
diseases is necessary (20).
Thc applicability of utility instruments to the
clinical setting has yet to be determined. Certainly, a
595
measure that combines risks and benefits of treatment
into a single value, as the utility measure does, would
theoretically be clinically useful. Utilities provide us
with a common unit of health impact. They therefore
permit cost-utility analysis among alternative programs with different effects. This type of comparison
may be used by people involved in health services
resource allocation and policy making to determine the
overall value of therapeutic interventions in the patient
population as a whole.
Arthritis-specific instruments. Specific instruments provide more specialized information in a concise way. Arthritis-specific measures focus on aspects
of health targeted toward arthritis and arthritis symptom complexes. Frequently used arthritis-specific
measures of health status include the AIMS. the
American Rheumatism Association functional class,
the Functional Status Index (FSI), the Health Assessment Questionnaire (HAQ), the Lee functional status
instrument (Lee), and the Toronto Questionnaire (TQ)
(25-31).
The AIMS is a self-administered questionnaire
that assesses physical, emotional, and social wellbeing. Within the questionnaire, information about the
severity of disease, health perception, other significant
illnesses, and sociodemographics is also gathered. In
intervention studies, while correlations have been
shown across dimensions, it appears that 3 dimensions
(physical function, psychological function, and pain)
warrant individual assessment (25). When used in
tandem with conventional clinical outcome measures,
the AIMS is able to detect clinically meaningful differences between drug-treatment groups.
The ARA functional classification system was
developed by Steinbrocker in 1937 to classify the RA
population for the purpose of research studies (26).
Change in functional ability has been detected using
this instrument in controlled trials of RA therapy.
However, lack of sufficient detail of individual activities limits its use for serial quantification of function.
The FSI was developed as both a clinical and an
evaluative tool to assess quality of life in geriatric
arthritis patients in the community. Forty-five activities of daily living are assessed 3 times for ratings of
dependence, difficulty, and pain. The € 3 1 has been
shown to be valid and reliable, but details about
sensitivity to clinically important change have yet to
be established (27). Interviewers require 60-90 minutes to complete the administration of this questionnaire.
The HAQ is a self-administered questionnaire
596
that measures 4 dimensions: disability, discomfort,
drug side effects, and dollar costs (28.29). Although it
was initially devised to assess functional capacity in
RA, it has subsequently been demonstrated to be
useful in a variety of other diseases (refs. 28 and 29,
and Fries JF: unpublished observations). In addition
to evaluating activities of daily living (ADL) components, the HAQ examines the level of difficulty the
patient is experiencing with these ADL and the degree
of assistance (from people or devices) required by the
patient. The modified HAQ, an 8-question tool reduced from 20 questions in the parent instrument,
incorporates the assessment of patient satisfaction. It
has indicated that patient dissatisfaction may determine the number of patient visits to the physician and
physician therapeutic intervention (32).
The Lee instrument measures both self-reported
activity performance and degree of difficulty encountered with activity. This instrument produces statistically
significant correlations with familiar outcome measures,
such as joint count, grip strength, walking time, and
functional class (33).
The TQ, first developed in 1979, assesses function in personal care, upper extremity activities, mobility, work, and leisure activities. Rehabilitation paramedical personnel and rheumatologists created the
weighting scale for responses (31).
There are 2 newly developed tools designed to
assess the quality of life of the individual arthritis
patient. They include the McMaster-Toronto Arthritis
Patient Preference Disability Questionnaire (MACTAR) and the National Institutes of Health Activity
Record (ACTRE) (34-37).
The MACTAR consists of both a patient preference questionnaire with which patients rank their
functional activities in order of importance, and a
global question about improvement in arthritis status.
By assessing mobility, self-care, work, and leisure, the
emphasis of the MACTAR is primarily on physical and
social function. Clinically important change in function has been demonstrated by serial assessment of
RA patients in a controlled trial (34). This questionnaire can be used only by a trained interviewer.
We have developed a modification of the MACTAR, the Problem Elicitation Technique (PET), to
incorporate the dimension of the level of difficulty or
frequency for each identified patient problem into the
MACTAR patient-generated problem list. The administration time is 10-20 minutes. Recognized limitations
of the MACTAR include its unconventional method of
calculating change and a current lack of knowledge of
BELL ET AL
the reliability and stability of patient preferences during a stable functional period. It is possible that the
addition of priority designations to existing, wellstudied and standardized tools may provide the same
information as the MACTAR without the additional
cost in time and personnel required to perform the
structured interview (38).
The ACTRE is a recently developed tool in
which the patient documents his or her level of physical activity in half-hour blocks of time, for 2 consecutive weekdays (35-37). Activities are categorized as
rest, physically active periods, sleep, and planning and
preparation. Each activity is rated for the level of pain
or fatigue, level of difficulty, and value to self and
others. An index of physical activity may be calculated
by totaling the number of rest periods and dividing this
figure by the total hours of physical activity. The ratio
reflects the balance of rest with activity. When used in
a prospective, randomized trial of an occupational
therapy educational intervention, the experimental
group increased the activity index and achieved a
better balance between rest and activity than the
control group. This finding approached statistical significance (P = 0.07) in a small sample (35,37). Additional details of its measurement characteristics and
usefulness both in clinical trials and practice settings
are pending (36). Further development within the field
of functional status evaluation is required.
How could I use them?
Although clinicians routinely evaluate the quality of life of their patients, this evaluation tends to be
informal. Validated quality of life instruments have
not, as yet, been used extensively in clinical practice.
Potential reasons for limited use include concerns
about the time and cost for administering these questionnaires, clinician inability to interpret the scores
and use the scores clinically, and a belief that the
information provided by such tools is available
through conventional testing.
Information provided by quality of life instruments has been shown to be useful in clinical practice
for determining prognosis. The data may also be used
for the targeting of interventions. Intervention targeting is made possible by using the results of these
measures to identify current patient problems, define
needs, set therapeutic priorities, and direct interventions. For example, a patient with polyarthritis and an
unstable, painful knee may identify stair climbing as an
area of difficulty. He or she may be unable to indepen-
OUTCOME MEASUREMENT IN RA
dently climb stairs to the second level of his or her
home, where the bedroom and bathroom are located.
This may be reflected in low scores in the areas of
independence, self-esteem, and functional level. Such
traditional measures as the joint count would not
necessarily identify the importance of the knee as the
target for therapy. Therapeutic objectives may include
pain relief, stabilization of the affected knee with
physiotherapeutic exercise and resultant muscle
strengthening, external bracing or performance of a
surgical procedure, and/or environmental adaptation.
Continuous monitoring of functional status during the
course of disease and therapy will assist in the evaluation of the effect of each specific intervention.
The clinical usefulness of 2 functional status
instruments, the AIMS and the HAQ, has recently
been described. Wolfe et a1 administered the patient
function portion of the HAQ to a cohort of 400 RA
clinic patients over a period of 3.1 years (39). The
questionnaire was self-administered and sent to the
patient population by mail every 6 months. Data on
health care use and cost were obtained, with patient
permission, from institutions and physicians. The patient function subsection of the HAQ correlated well
with traditional clinical variables, psychological variables, and the erythrocyte sedimentation rate. This
section reflected change over time, similar to the
change reflected by the clinical variables. It was easy
to administer, and took the patient approximately 13
minutes to complete. The scoring system was simple
and brief. The provision of a classification description
with which the scores could be compared made the
test scores comprehensible and clinically useful.
The clinical use of information provided by the
AIMS instrument has also undergone initial testing.
Kazis et a1 have developed and tested an AIMS
summary patient profile format (6). Two hundred
rheumatologists and 200 allied health professionals
evaluated 10 patient profiles. The profile was a computer-generated, single-page, health status summary
report. Each patient profile consisted of the 9 health
status scales, the mean score on each scale for the RA
population, and comments highlighting key tasks with
which the patient was having difficulty. The profile
format was shown to be reliable and valid. The profiles
were understandable and permitted interpretation of
health status across a spectrum of dysfunction. The
impact of the knowledge of patient health status on
clinical practice has yet to be determined. We await
the results of a randomized controlled trial using this
tool.
597
The usefulness of the results provided by quality of life instruments for the targeting of interventions
is theoretically sound and is currently being tested.
The assistance these measures provide in the determination of prognosis has been demonstrated and bodes
well for their use in the future.
How well do these instruments perform when
their measurement characteristics are tested?
The content strengths and weaknesses of the
various arthritis-specific questionnaires and general
health questionnaires are outlined in Tables 2 and 3.
The AIMS and the SIP have the broadest coverage
with regard to content. The format of the selfadministered questionnaires (AIMS, HAQ, and SIP) is
useful for the office practice. The patient could complete the questionnaire in the reception room while
awaiting review. The requirement of an interviewer for
the MACTAR and PET is a drawback for these
individual measures. However, it may be worth the
expense, with regard to human and monetary resources, to document the disability most important to
the specific patient. Within the population of patients
studied by use of these questionnaires, there has been
good acceptability.
Comparative analysis of the AIMS, HAQ,
QWB (IWB), and SIP with the standard FSI (7), and
the Lee, MHIQ, and MACTAR with the joint count
(40) using relative efficiencies (change relative to the
standard measure) has demonstrated that they are all
capable of detecting change. There are minor differences in their ability to detect this change in the
different dimensions. Both the AIMS and the SIP
measure functional change equally well, and the HAQ
and SIP are better measures for determining change in
social function than is the AIMS (7). Until results are
reported showing that one instrument is superior to the
others for the individual patient, it would seem reasonable for the practicing rheumatologist who is following a group of office or clinic patients to select the
instrument with the items that best reflect his or her
own priorities.
How should I evaluate any new quality of life
measure?
A list of methodologic considerations has been
developed that can be used to compare and evaluate
the usefulness of quality of life instruments (41). These
598
Table 4. Methodologic considerations for quality of life instruments
1. Purpose
2. Comprehensiveness
3. Credibility
4. Accuracy
5 . Sensitivity to change
6. Biologic sense
7. Feasibility
guidelines have proven to be useful in surveying
previous work and have helped identify research questions that remain to be addressed (Table 4).
Purpose and comprehensiveness. When evaluating a new instrument, the first question the clinician
should address is “Is the purpose of the instrument
clearly stated?” The components being evaluated
should be obvious, the target population defined, and
the disease for which the measure was developed
should be outlined. The second question is “Are all
relevant dimensions of function included?” The content of the instrument should reflect those areas of
interest to the clinician and the patients.
Credibility. In evaluating the credibility of the
instrument, it is important to ask “Does the instrument possess face validity?” The method of measuring
the outcome of interest should seem reasonable and
possible. The authors should have attempted to show
that the instrument is measuring what it is intended to
measure. Questions should be specific and should
refer to a designated time period. The recall time
should also be appropriate to that of the age group
being addressed.
“Do the questions assess level of ability at a
particular point in time or change in ability over
time?” When looking for the effects of an intervention
on patient outcome, a measure of change over time is
most appropriate. “Are the questions capacityoriented or performance-oriented?’’ Capacity-oriented
questions ask the patient about his or her ability to
perform a task. Performance-oriented questions ask
the individual if he has actually completed a specific
task. Performance questions are a more accurate
reflection of an individual’s actual function. However,
capacity questions may be more meaningful in
practice.
“Are the responses to individual questions aggregated into a summary score?” A summary score
may allow the clinican to compare the individual
patient with the overall patient population, as well as
to numerically compare individual patient status over
time. Interpretation of summary scores requires ac-
BELL ET AL
cess to group means for the normal and diseased
population. The last question relating to credibility is
“Was this assessment tool developed and pretested
for the purpose for which you want to use it?” Tools
developed with the same purpose for which you want
to use them will perform better for you.
Accuracy. To determine the accuracy of a measure, you must first ask “Are the results reproducible?” When evaluating the new instrument, one
should look for results on test-retest and intraobserver-interobserver reliability. Next, you should ask
“When compared to a more accurate measure, does it
perform satisfactorily?” The clinician would be wise
to determine if the data obtained with the new instrument have been compared with those obtained from an
established, more accurate or similar instrument.
Sensitivity to change. To determine this feature
of a measure, it should be asked “Is it sensitive
enough to detect clinically important changes across
patients and within patients?” To answer this question, it is necessary to know the results of empirical
studies using the new instrument plus another instrument in patients with the disease in question and with
established change over time.
Biologic sense. “Does it perform satisfactorily
when compared with another similar assessment?”
The instrument should be tested in conjunction with a
more accurate measure of change, such as a change in
clinical parameters.
Feasibility. The feasibility of using any new
instrument in clinical practice may be determined by
positive answers to the following questions. “Is the
format for administration appropriate for your purpose?” “Is the time to administer the questionnaire
appropriate for your purpose?” “Are the questions
easy to understand and acceptable to the patients and
the interviewers?”
These questions are offered as guidelines for the
clinician in the position of reviewing a new or existing
instrument and will assist him or her in the endeavor of
choosing an instrument appropriate to their situation.
Is the state of the art sufficiently advanced
that drug approval agencies should require
quality of life data before approval?
Cananadian and American drug approval agencies currently do not require assessment of the impact
upon quality of life in the “pivotal” studies of arthritis
patients that are used for registration of the drug. A
global assessment of health status completed by both
599
OUTCOME MEASUREMENT IN RA
the patient and the clinician is required, but the only
functional end point usually included is the Steinbrocker scale. This scale was designed in the 1930s,
and it does not satisfy any of the key psychometric properties such as sensitivity/responsiveness to
change. This major drawback has led to the revision of
the Steinbrocker instrument by the American College
of Rheumatology subcommittee on functional status
and disease severity in RA.
A strong argument can be made that the addition of a validated quality of life scale to all clinical
trials would complement the anthropomorphic, c h i cal, and laboratory data. This was recommended by a
number of investigators in the field at a recent conference (September 1988 in Washington, DC) sponsored
by the Arthritis Foundation, which focused on the
development of disease-modifying antirheumatic
drugs. Health status is as important or is more important to the clinicians and patients than the traditional.
currently required end points. Evidence is accumulating that health status is as important as other end
points in predicting long-term outcome, such as progression of disability and death.
The end points currently in use tell only part of
the story. For example, one of the end points used by
most approval agencies is improvement in the joint
count. What they fail to consider, however, is that
improvement in 1 important joint that affects functional activity (such as the hip) may have a greater
impact on the patient’s functional capacity and quality
of life than would improvement in 8 of the less
important joints. As described above, there are a
number of both disease-specific and generic health
questionnaire instruments that are as quantitatively
accurate and useful as the traditional end points currently used. A further argument can be made that both
disease-specific and generic transcondition questionnaires should be included, for the following reasons.
General health status instruments are essential for
comparisons across conditions, especially for the use
of third-party payors. Disease-specific instruments are
important so that insensitivity to change that results
from the inclusion in generic instruments of items of
low frequency or irrelevance to arthritis, which leads
to statistical noise, can be avoided. The investigator
setting up new studies should be free to select any
of the validated instruments on the basis of the riskresponse profile of his or her patients and the environment or the intervention. This addition should
complement the anthropomorphic, clinical, and laboratory data.
What will the future bring in the way of
further development of these measures?
Reviews of currently available instruments
have led prominent methodologists such as N v an
Feinstein to identifying some major shortcomings of
the quality of life questionnaires. These include 1) lack
of attention to the role of the patient in the effort or
support of the performance being measured, 2) using
the same Scale for aSSeSSmentS that really require
different types of expression, 3) assuming the suitability of a profile or an aggregated index for all situations,
4) incompletely evaluating the measurement characteristics of old and new measurement tools, and 5 )
applying the tool in a setting or for a purpose for which
it was not designed (42). Feinstein and colleagues’
concern regarding the lack of attention to patient
priorities and preferences has been addressed by the
evolution of the MACTAR, PET, and ACTRE patientspecific questionnaires, and the PUMS, SG, TTO, and
WTP utility questionnaires.
In addition to these drawbacks, other shortcomings can be outlined. Items included in these
questionnaires may not show any level of impairment
present due to the disease or condition of interest. For
example, if arthritis affects only the upper limbs, items
that relate to the lower limbs, such as mobility, are not
impaired, and there is therefore no room for improvement. Also, the items that are present may not have
the potential to improve with the intervention of
interest. Disability resulting from severe joint damage
without active inflammation will not respond to antiinflammatory or cytotoxic medication. Clinicians have
also noted that the results from these instruments are
not presented in a format that is understandable to
both themselves and to the policy makers. Finally, the
applicability of the results to the individual patient and
in clinical practice is unclear.
In the years to come, the predictors of good and
bad functional responses will be determined. The use
of alternative study designs for assessing the impact of
therapy upon the quality of life may be necessary.
Different instruments may have different strengths and
weaknesses when used in single-subject studies, surveys, case-control, and controlled trials. In addition,
the presentation of results requires reevaluation. Currently, drug development studies, even those with quality of life data, are oriented to aggregating efficiency data
and to disaggregating toxicity data. The complement to
each of these is the need for further quality of life studies.
Approaches that allow the clinician to compare benefi-
BELL ET AL
600
cial with detrimental effects upon the function of an
intervention need investigating.
Summary
In 40 years of development in the area of quality
of life, the goal of applicability to the individual patient
has not been accomplished. During the 1980s, we
strived to improve the applicability of these instruments by refining disease-specific measures and developing patient-specific measures so that the sensitivity
of these tools to clinically important change could be
increased and comparative indices across conditions
could be established. Finding the balance between
brevity, reliability, and comprehensiveness will improve practicality. The reliability of serial measurements using the various instruments in individual
patients and in small groups of patients needs to be
established. In the absence of a gold standard, validity
will continue to be derived from testing new measures
against accepted clinical measures.
The ideal tool for use in clinical practice has not
yet been developed. At this time, the clinician may
choose among the many reliable and valid questionnaires assessing functional status, health status, and
utility, according to his or her purpose. The information gathered from these instruments may help identify
patients’ problems, set treatment priorities, direct
interventions, monitor the longitudinal course of disease, and assist in program evaluation and policy
planning.
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New Manuscripts to be Sent to Dr. Peter H. Schur
Dr. Peter H. Schur will officially assume the full responsibilities of Editor, Arthritis and Rheumatism,
on July 1, 1990. As part of the transition from the Editorship of Dr. William J. Koopman, Dr. Schur
will handle the review process for all new manuscripts submitted after April 1, 1990. Manuscripts
should be sent to Peter H. Schur, MD, Editor, Arthritis and Rheumatism,Arthritis and Rheumatism
Editorial Office, Room 422, Richardson Fuller Building, 221 Longwood Avenue, Boston, MA 02115.
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