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11
Measuring Pain and
Dysfunction
This chapter explores the technical feasibility of
measuring chronic pain and related dysfunction.
It addresses questions of whether the severity of pain can be docu-
mented and whether the relation between pain and the ability to work
can be assessed. The Social Security Administration (SSA) considers
these questions to be crucial to disability evaluation of pain patients.
Physiological and neurological techniques for measuring pain were
described in Chapter 7; this chapter examines psychological, behav-
ioral, and functional methods for assessing pain. Measures of con~-
tions such as depression and anxiety are not discussed because these
have been thoroughly reviewed elsewhere (see Anastasi, 1983; Evans,
1983; L`ehmann, 1985; Spielberger et al., 19841. Some of the methods
discussed here are appropriate for the assessment of work disability for
compensation purposes; others are more appropriate for use by clini-
cians diagnosing and treating pain patients.
In order to pursue its mandate to conduct a state-of-the-art evalua-
tion of pain assessment methods, the Institute of Medicine (IOM) study
committee reviewed the literature and invited a panel of six experts in
pain measurement and related matters to make formal presentations
and participate in a discussion at one of its meetings (see list of
panelists at end of chapter). Topics reviewed with the panelists
included physiological measures of pain, subjective and behavioral
observation techniques, assessment of the meaning of pain, physical
function measures and vocational assessment in chronic pain patients,
and the assessment of psychosocial and psychiatric factors in the
211
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212 ASSESSING ED TREATING PMN ED DYSFUNCTION
etiology and maintenance of chronic pain and dysfunction. In later
meetings the issues of assessing pain and functional capability were
discussed repeatedly and considered in light of disability evaluation.
BASIC CONCEPTS OF MEASUREMENT
Measurement is the process of assigning numbers to specific proper-
ties of events, processes, objects, or persons. All measurement involves
error to varying degrees. Number assignment, or scaring, may involve
different degrees of precision. It can tee used to categorize or classify items
or individuals (e.g., 1 = male, 2 = femaTe) or to rank order them. In some
cases, number assignment is sufficiently precise to justify mathematical
manipulation of scores. The depth of scientific inference permitted by
measurement depends on the precision of the scaling used.
In some cases the attributes or properties being measured are
hypothetical, being derived from a theory or model, rather than an
object or event that can be objectively observed. Human pain, like
intelligence, cannot be directly observed but may be scaled along one
or more dimensions in accordance with theory or highly specific
models. Pain measurement is never Theoretical; every too! is rooted in
a fundamental conceptualization of pain or at least certain basic
assumptions that may or may not be explicitly defined by its users.
There are both medical and nonmedical conceptual models for pain.
In each of these broad categories, there are several subcategories.
Medical moclels share the basic assumption that pain is a symptom of
an underlying pathology. Nonmedical models, which are largely psy-
chological in nature, construe pain as a perception, as a behavior, or as
. .
a cognition.
The distinctions between the various models are complicated by the
basic distinction between acute and chronic pain. Some models can
account for one type of pain but not the other. In general, medical
models are best suited for explaining acute pain problems in which
pain is a direct fimction of nociception, whereas nonmedical models
can best account for chronic pain problems in which the relation
between tissue damage and pain complaint is weak or lacking. In
practice, medical and nonmedical models can be, and often are,
combined.
The multiplicity of models available for quantifying pain attests to
the early stage of development of this area of research. The lack of a
unified theoretical perspective has both advantages and disadvantages
and is probably a necessary stage in the long-range development of
science in this difficult area. On the positive side, the combination of
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MEASURING PAIN AND DYSFUNCTION 213
medical and nonmedical models is a more powerful approach to pain
assessment and control than the use of either model alone. On the
practical, clinical level, measures derived from multiple models may
provide a mosaic of information that promotes a clearer understanding
of the patient than the medical model alone.
The primary disadvantage of variation in theoretical perspective is
inconsistency in the resulting measurement technology. Operational
definitions of pain vary greatly, and the data gathered by one inves-
tigator may be of little or no use to another. In addition, investigators
sometimes disagree with one another about precisely what is being
measured. For example, as discussed in Chapter 9, pain may be a
symptom of depressive disorder. a consequence of it, or a problem that
coexists with depression. Depression, then, may be an independent
variable for one theorist and a dependent variable for another. The
lack of consensus on the role of affect in chronic pain is a major
impediment in the progress of pain measurement technology.
MEASUREMENT TOOLS
Most pain measurement involves either structured self-report of
pain, observation of patient behavior, or some combination of the two
approaches. When self-report methods are used, instruments should
(1) burden patients minimally, (2) be understood by patients, (3) yield
a wide range of scores with sensitivity to analgesic intervention, and
(4) demonstrate appropriate reliability and validity. Observational
methods for the scaling of pain need not be understandable to the
patient, but they must fulfill the other three criteria and, in addition,
protect the patient's right to privacy. The major methods for scaling
pain and their advantages and limitations are discussed below.
Measurement of Subjective Pain States
Measurement by subjective report is by far the most common type of
procedure for quantifying pain. Patients may indicate pain levels
verbally, mark simple scales, or fill out complex questionnaires. In all
cases, the patient determines the data.
Self-Report: Data from Introspection
Many investigators hold that pain is inherently a private experience
that can only be quantified by asking the patient to do his or her own
number assignment. There are both unidimensional, or simple, scales
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214 ASSESSING ED TREATING Ply ED DYSFUNCTION
tor pain measurement and multidimensional, or complex, methods to
obtain data.
Self-Report Methods Using a Single Dimension
The simplest approach to assessing subjective pain states is the use
of category scales. Usually the intensity dimension is scaled, but
category methods can scale aversiveness or some other quality of pain
as well. Such scales require only simple choices of the best descriptors
from the patient. For example, MeIzack and Torgerson (1971) intro-
duced the following scale for pain intensity: "mild, discomforting,
distressing, horrible, excruciating." Statistical treatment of category
data is usually restricted to nonparametric methods, and this restrains
the interpretation of the data gathered. Moreover, respondents tend to
use the middle of the scale.
An alternative is the Visual Analog Scale (VAS), which usually
consists of a 10-cm line anchored at one end by a label such as "no pain"
and at the other end by "the worst pain imaginable" or "maximum pain."
Respondents mark the line to indicate pain intensity; the mark is scored
on either a 1-10 or a 1-100 scale. The Numerical Rating Scale (NRS) is
a variation of the VAS in which patients rate their pain on a ~10 or
~100 scale that is discrete rather than continuous.
Although these tools are expedient, researchers have repot ted that 7
to 11 percent of patients are unable to complete the VAS or find it
confusing and about 2 percent are not able to use the NRS (Kremer et
al., 1980; Revill et al., 1976; Walsh, 19841. Carisson (1983) critically
reviewed the VAS as a method for scaling pain states or pain relief in
chronic pain patients, and she compared different forms of the scale.
Reliability, as judged from consistency of responses to two forms, was
Tow, and CarIsson concluded that the validity of VAS procedures for
chronic pain populations may be unsatisfactory.
The VAS is a straightforward, efficient tool for scaling pain, but it
can fad] if care is not taken to ensure accurate, valid, and reliable
reporting. Such instruments will continue to be used because of their
expediency, minimal respondent burden, and face validity. However,
in addition to the limitations in reliability, these tools may oversim-
plify the pain experience.
Self-Report of Pain in Several Dimensions
The scientific value of the VAS is restricted by its unidimensional-
~ty. Some investigators adjust for this by using more than one VAS,
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MEASURING PEN ED DYSFUNCTION 215
with each designed to assess a different dimension of pain. However, it
is hard to ensure that the response to the first scale a~ninistered does
not influence the response to subsequent scales (Carisson, 19831. There
are several multidimensional scales that avoid some of the problems
with VAS but increase responder burden and cost more to interpret.
The McGill Pain Questionnaire (MPQ) is perhaps the most thor-
oughly evaluated multidimensional scaling device for pain. It is based
on the vocabulary used by patients to describe various experiences of
pain. The MPQ scales pairs along three dimensions: sensory, affective,
and evaluative. There are 20 sets of words that describe varying
qualities of pain. Ten of the sets represent sensory qualities, 5 are
affective, and 1 is evaluative. Each set has from two to six words that
vary in intensity for the quality described by the set (e.g., from hot to
searing, from annoying to unbearable). Patients are instructed to
select the sets that are relevant to their pain and to circle the words
that best describe it within each selected set. An adjunct test device,
the Dartmouth Pain Questionnaire, has been offered to supplement the
MPQ through the assessment of four additional factors, including
impaired functioning (Corson and Schneider, 1984~.
Many studies support the factor structure of the MPQ, its reliability,
and its concurrent validity (see Shale and Chapman, 1984; Chapman
et al., 1985~. However, it places a large responder burden on the
patient, some patients cannot handle the vocabulary of the instru-
ment, and the scoring procedures available are limited (Sy~ala and
Chapman, 1984~.
Turk, Rudy, and Salovey (1985) critically evaluated the MPQ and
various approaches to scoring it. They concluded that the total score is
valid as a general measure of pain severity but that individual scale
scores should not be used; adequate discriminant validity to support
scaling at the level of sensory, affective, and evaluative dimension
subscales could not be demonstrated. Meizack has responded to these
challenges by pointing out that the high intercorrelation among the
factors of the MPQ does not necessarily indicate a lack of discriminant
validity and by reviewing an impressive number of studies that
demonstrate the discriminant capacity of the instrument (Meizack,
1985).
The West Haven-Yale Multidimensional Pain Inventory is an alter-
native instrument designed to be briefer and more classical in its
psychometric approach to multidimensional scaling than the MPQ
(Kerns et al., 19853. The 52-item inventory is divided into three parts:
(1) five general dimensions of the experience of pain and suffering,
interference with normal family and work functioning, and social
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216 ASSESSING~D TREATING PANNED DYSFUNCTION
support; (2) patients' perceptions of the responses of others to displays
of pain and suffering; and (3) the frequency of engagement in common
daily activities. The instrument is derived from cognitive-behavioral
theory and assesses such constructs. As such, it represents a very
different approach to scaling than the MPQ.
The Brief Pain Inventory is an efficiently administered multidimen-
sional pain questionnaire with demonstrated reliability and validity in
cancer and arthritis patients (Daut et al., 1983; Cleeland, 19855. In less
than 15 minutes, patients can report analgesic medication use, pain
relief from drugs, beliefs about the cause of pain, qualitative descrip-
tions of pain, areas in which pain interferes with quality of life, the
pain's locus, and their worst, average, and current pain level on a 0~10
scale. This measure has proved useful as a multidimensional pain
measure in patients with progressive disease.
Other approaches to the multidimensional scaling of pain have been
derived from a psychophysical technique known as cross-modality
matching in which a sensory experience is quantified by matching it to
the experience of a precisely controlled stimulus in a different sensory
modality. For example, a laboratory subject might match the intensity
of a toothache produced by electrical tooth shock to the loudness of a
controlled tone in decibels. Analogous methods are used for clinical
pain scaring. The typical procedure involves matching words describ-
ing pain to line length or handgrip force, matching both to experimen-
tal pain, and then deriving scaling standards for the relationship of
words describing pain to actual pain. The methods can then be applied
to clinical pain assessment. This can be done for multiple dimensions
of pain, such as intensity and unpleasantness (Gracely et al., 19791.
The Pain Perception Profile (Tursky et al., 1982) uses cross-modaTity
matching scaling procedures. It (1) quantifies the sensation threshold;
(2) uses magnitude estimation procedures to judge induced pain; (3)
scales pain on intensity, reaction, and sensation dimensions using
psychophysical scaling of verbal pain descriptors; and (4) permits the
psychophysically scaled verbal descriptors to be used in a diary format
for repeated assessment over time.
Compared to the MPQ, cross-modality scaling methods are shorter
and less demanding. Yet they over potentially more reliable and valid
data than the simpler VAS scales. However, the Pain Perception
Profile and Graceley's methods (Gracely et al., 1979) have not yet been
validated for different patient populations. Such work would require
experimental pain testing and a substantial amount of development
before clinical data from a broad sample of patients could be inter-
preted confidently.
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MEASURING PEN ED DYSFUNCTION 217
Pain as Behavior: Observational Data
Pain Judgments by Health Care Providers
Health care providers generally use two types of pain assessment
that can be more or less structured: patient classification and observer
ratings of patients' pain problems. The most basic form of observer
scaling is patient classification. Typically, medical history and diag-
nostic data are used to categorize chronic pain patients. For example,
Hammonds and Brena (1983) devised a four-category classification
scheme for patients in which Class ~ consisted of those with high
behavioral determinants and low organic determinants of pain, and
Class lI patients were Tow both on behavioral and organic determi-
nants. Class ITI patients had high scores both on organic pathology and
pain behaviors, and Class IV patients had high organic pathology and
Tow pain behavior scores. Advocates of such approaches point to the
value of such categorizations for screening and selecting appropriate
interventions. Others, however, believe that such methods are over-
simplified, that most patients do not fit neatly into a category, and that
such categorization may affect the patient's care inappropriately.
When pain is directly scaled by health care providers observing the
patient, simple rank-ordered category scales are typically used, such
as no pain, slight pain, moderate pain, and severe pain. Often, such
scales may include an evaluation of what the patient can or cannot do
on certain tasks, such as bending over to pick up a weight.
There are several limitations of observer pain judgments in chronic
pain settings. First, most investigators hold that such judgments are
not true measurements: Pain can never be observed by another
individual, it can only be inferred from a patient's actions. Second,
knowledge of a patient's clinical findings can bias the pain rating.
There is also the danger that raters will stereotype patients on the
basis of age, sex, or race. Use of multiple raters who are trained with
well-defined criteria for assessing pain can reduce these problems.
Measurement of Pain Behavior
Although pain may not be objective, the behaviors of patients in pain
may be observed, and scored, objectively. Pain behavior is a normal
response to an injurious stimulus, but when it occurs in the absence of
such a stimulus or too small a stimulus, it may be described as an
abnormal behavior. Behaviorists generally do not seek to infer pain
from behavior; instead, they view pain behavior itself as the problem;
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218 ASSESSING ED TREATING PEN ED DYSFUNCTION
and it is pain behavior, rather than some hypothetical personal state,
that they seek to correct therapeutically.
Patients in pain exhibit certain consistent behavior patterns. For
example, studies have shown that back pain patients tend to grimace,
guard their movements, rub themselves, and sigh (Keefe and Hill,
19851. When clinical pain is operationally defined in terms of such
behavior patterns, objective measures can be used. Certain behavior
patterns can be identified as being related to pain, quantified in terms
of frequency or rate of occurrence, and assessed via direct or videotape
observation of patients in selected settings performing specific tasks.
Because behavioral patterns are complex, most behavioral measures
are multidimensional. The identification and quantification of pain
behaviors varies greatly with different types of pain problems. In
general, behaviors are tallied over time and scored in terms of their
frequency. Keefe and Block (1982) developed an observational scoring
system for scoring pain behavior in chronic back pain patients.
Guarded movement, bracing, rubbing, and sighing were assessed.
These indices proved reliable, valid (in relation to reported pain), and
more frequent in pain patients than in normals or depressed controls.
Keefe and Hill (1985) extended the observational approach by using
a transducer placed in the patients' shoes so that walking parameters
could be assessed. Patients and nonpatients were required to walk a
5-m course while being videotaped. Patients walked more slowly than
normals, took smaller steps, failed to show normal symmetrical gait
patterns, and exhibited more pain behaviors. This approach appears
promising for assessing and objectively quantifying back pain behav-
iors. More generally, repeated recordings could be used to document
changes in an individual patient's behavior over time for use by
physicians or by disability examiners. In the latter instance, such
recordings could provide some information that would otherwise be
available only by a face-to-face encounter.
A major limitation of the behavioral approach is that pain behaviors
are highly specific for each pain syndrome. Patients with shoulder pain
or headache, for example, would probably be indistinguishable from
healthy people on Keefe and Hill's (1985) test. Keefe and his colleagues
(1985) undertook behavioral evaluations of patients with head and
neck pain to address this issue. They found that such patients dis-
played their pain primarily through their facial expression rather than
through guarded movements.
Broad indicators of pain behaviors with potential application to
different clinical populations do not appear promising. Linton (1985)
hypothesized that reported pain intensity is inversely related to
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MEASUP`ING PAIN AND DYSFUNCTION 219
general activity level in back pain patients (as measured by self-
monitoring or observed behavior in a test situation). He found no
relation between the level of patient activity and chronic pain inten-
sity. Thus, behavioral indicators appear well suited as highly specific
and precise ways to quantify certain outward pain behaviors, but they
may not serve well as global indicators of subjective pain intensity.
Further work is needed before the behavioral approach can quantify a
wide range of chronic pain problems.
Mixed Methods: Self-Reports of Pain Behaviors
One way to gather information about behavior patterns and habits is
to ask the patient, his or her spouse, or some other day-to-day observer.
The pain diary is perhaps the most commonly used form of behavioral
self-report. A typical pain diary is a Tog of daily pain-relevant activity
broken down into small blocks of time. Activities may be divided into
sitting, walking, and reclining, with the patient filling in the specific
activity under the appropriate category according to the time the
activity occurred. Pain ferret is rated on a ~10 scale for each hour, and
medications may also be recorded.
There are several potential advantages to using a pain diary with
chronic pain patients. First, because the diary is completed daily, it is
not subject to distortion based on the patient's current pain experience
at the time he or she is seen in the clinic. Variations in pain levels
during the day and from day to day can be recorded. Second, the diary
yields data on patterns of normal activity relative to patterns of pain
behavior (or pain-linked inactivity) not available from other behav-
ioral assessments. In addition, it gives information about patient
behavior in the home setting. From the pain diary one can determine
behavioral patterns, defined in terms of the time of day or activity, that
result in high pain versus average pain levels. It can also reveal time
spent in various activities or inactivity over a week and help define the
relation among pain, activity, and medication use.
Iwo limitations should be borne in mind when considering pain
diaries. First, their reliability is unknown and varies from person to
person because diary data are dependent on the accuracy of recording.
Second, whereas some people complete the form on a daily or hourly
basis as directed, others do it incompletely or retrospectively just
before their appointments. Furthermore, it is not known whether the
experience of keeping a diary affects the experience of pain itself.
Certainly, the diary calls attention to the pain and its influence on
day-to-day activity. This issue awaits formal study.
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220 ASSESSING kD TREATING PEN ED DYSFUNCTION
The pain diary method combines the simplicity and efficiency of self-
report methods with the theoretical perspective of the behaviorist.
However, pain diaries presuppose that the patient (or the spouse) is a
reliable and accurate historian. Ready, Sarkis, and Turner (1982)
found that chronic pain patients, when asked to report medication use,
gave information that was 50~0 percent below their actual drug
intake. Kremer, Block, and Gaylor (1980) compared patient records
with staff observations of patients' social behavior and found discrep-
ancies. Sanders (1983) studied automatic monitoring of time spent out
of bed ("uptime") in normal controls, psychiatric inpatients, and
chronic back pain patients. He found moderate positive correlations
between self-reports and automatic monitoring. All groups averaged
less self-reported uptime than the automated report indicated, with
the discrepancy being greatest for the chronic back pain patients.
Thus, the validity of the mixed methods approach as a measure of pain
is questionable.
RELATED MEASURES OF DISABILITY
Pain and Functional Status
Of primary importance in assessment both in the context of medical
care and in determining eligibility for disability benefits is ascertain-
ing whether an individual is prevented from gainful employment or
otherwise normal living patterns by his or her condition. The chal-
lenge of assessing the patient's functional capability has attracted the
attention of several investigators, and a few have attempted to relate
pain to function.
Disability Assessment
The Northwick Park Activities of Daily Living Index has been
combined with a grading system (Parish and James, 1982) to produce
a way of assessing the level of functional independence of the disabled
patient. Basically, the assessment procedure records whether the
patient is independent or dependent on 20 different activities. There
are six self-care tasks, six stages of mobility, three employment grades,
and five types of domestic activity. This assessment procedure can be
performed quickly and repeated as often as needed. However, it is
better suited to the assessment of severely impaired individuals than
to workers with pain complaints.
Yvette (1980) has offered an approach to assessing the functional
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MEASURING PEN ED DYSFUNCTION 221
capability of noninstitutionalized persons with polyarticular condi-
tions. Activities of daily living were examined in the assessment
process. Five categories (physical mobility, transfers, home chores,
kitchen chores, and personal care) accounted for more than 50 percent
of the variance in the data studied.
Sickness Impact
Persisting pain typically has a significant sickness impact on the
patient. For the low back pain patient (the most-studied type of patient
in the chronic pain population), this effect consists of increased hours
spent reclining or in bed rest, restriction of normal social and recre-
ational pursuits, emotional distress, and inability to maintain gainful
employment. The concept of sickness impact is for most practical
purposes interchangeable with that of disability.
No comprehensive, validated objective indicators of sickness impact
exist. Instead, behaviorally oriented subjective report procedures (like
those discussed previously) are used. Activity diaries, in which a daily
record is kept of uptime/downtime, medication use, and type of activ-
ity, can be used to assess the impact of chronic pain (Follick et al.,
1984~. A variety of scores can be tabulated and plotted over time from
diary forms, depending on their construction. However, it is possible to
go well beyond the daily diary in an attempt to systematically scale
physical, social, and psychological limitations imposed by (or adopted
in response to) sickness.
The most fastidiously developed and fully validated of such instru-
meets is the Sickness Impact Profile (SIP) (Bergner et al., 19811. This
instrument is designed to be a general indicator of health status and
health-related dysfunction rather than a pain-specific test. It can be
a~ninistered by an interviewer or self-administered. Patients respond
only to those sickness-related behavior change items that describe
them appropriately. The SIP provides general scores along three
dimensions of impairment physical, psychosocial, and work-recre-
ation and 12 specific category scores that include, for example,
communication, social interaction, and home management. Its mea-
sures are derived from responses to 136 items.
Follick and his colleagues (1985) investigated the SIP scores of 107
back pain patients seen at a multidisciplinary pain clinic; 75 percent of
the study patients were receiving Workman's Compensation. The
outcomes supported the validity of the SIP as an indicator of functional
status in low back pain patients. The psychosocial dimension of the SIP
was significantly correlated with the Minnesota Multiphasic Person
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222 ASSESSING ED TREATING PEN ED DYSFUNCTION
ality Inventory (MMPl); the physical dimension score was inversely
related to independent measures of standing andlor walking and
positively correlated with downtime. The investigators concluded that
the SIP is a useful means of assessing functional impairment in back
pain patients.
Chariton, Patrick, and Peach (1983) used items from an existing
health survey together with items from the SIP to produce a too] for
the multivariate assessment of disability. Five global classifications
for items were used: physical, psychosocial, eating, communication,
and work. The disability measures derived from the items related to
age and number of medical conditions but not to services utilization.
Mayer anti colleagues (1986) have developed a set of rehabilitation-
focused tests consisting of largely objective physical function measures
for use with low back pain patients. These tests, which were combined
with a battery of psychologic measures, included eight categories of
measurement: (1) range of motion, (2) cardiovascular fitness and
muscular endurance, (3) gait speed, (4) timed simulation of daily
activities, (5) static lifting, (6) lifting under load, (7) isometric and
isokinetic dynamic trunk strength, and (8) a global effort rating. These
measures were obtained repeatedly through the course of treatment of
back pain patients and provided information on functional capacity
both to the patient and surgeon. There was an initial unemployment
rate of 92 percent in the sample under study, and 82 percent of patients
returned to work after treatment. Although the measures derived were
not direct measures of pain, but rather measures of function, they
proved to be of great value in successful treatment. Despite the
successful rehabilitation of patients in this study, and with a signifi-
cant decrease of self-reported pain, these patients maintained a mean
VAS pain report score of 77 out of a possible 150. This suggests that
rehabilitation may be achieved without major pain relief.
Assessment of Work Performance
In recent years, a considerable amount of attention has focused on
the development of techniques to assess work-related function. Be-
cause direct assessment in the workplace is usually not possible
(Chaffin, 1981), various work simulation strategies have been devel-
oped. The most basic approaches involve direct measures of strength or
capability. For example, Harber and SooHoo (1984) used static ergo-
nomic strength testing as part of a multidisciplinary evaluation
program for occupational back pain. Lifting ability in several positions
was quantified. Because it was independent of the degree of impair-
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MEASURING PAIN AND DYSFUNCTION 223
meet, the degree of intrasubject variability could be used to detect
inadequate subject efforts. This approach seems promising but falls
short of true work simulation and may not be applicable to all types of
occupations.
The Liberty Mutual Medical Service Center in Boston uses work
simulation as part of the treatment for back pain patients (Bettencourt
et al., 19861. Balance monitors, pneumatic lifting and lowering equip-
ment, a multi-work station, a truck driving simulator, and an upper
extremity work simulator are available. The goal of the program is to
allow patients to improve work performance capability and stamina
while they learn to live with their symptoms. The setting has not yet
been a major resource for disability assessment. This type of program
is consonant with the concept of work hardening as an approach to
industrial rehabilitation (Matheson et al., 19851.
The adaptation of work simulation techniques to eligibility determi-
nations for disability programs is intrinsically appealing because they
offer promise to measure work-related function. However, a substan-
tial amount of development would be required to standardize the
measures and establish norms and parameters for specific kinds of
jobs.
Severity of Pain and Dysfunction
The relation between pain severity as defined by subjective report
and functional capacity has not been adequately studied. However, the
literature on contingency management and operant conditioning has
clearly demonstrated that the relation is not simple. Patients often fad]
to perform normal daily functions because they believe, or they have
been told by well-intentioned health care providers, that activity will
exacerbate the pain and worsen their health. But for many chronic
pain conditions the opposite is true: excessive rest and reclining
contributes to the persistence of pain, and activity is beneficial rather
than harmful to health.
Patients who undergo a rehabilitation program involving contin-
gency management typically increase their functional capacity with
programmed exercise (Fordyce, 1976; Doleys et al., 1982; Roberts,
19811. Some report that the pain disappears as normal activity
increases; others report that the pain remains but fades into the
background of daily life. The latter type of patient demonstrates that
at least some people can function in normal daily and vocational life
despite the presence of pain, once they understand and prove to
themselves through experience that activity is not harmful (see
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224 ASSESSING ED TREATING PEN ED DYSFUNCTION
Chapter 121. Still other patients are able to live reasonably normal
daily lives but find that the unique demands of their vocations
(typically manual labor) exacerbate the pain. In this case, vocational
rehabilitation is critical to fully successful treatment.
FACTORS BIASING PAIN MEASUREMENT
The accurate scaling of pain in a cooperative, intelligent respondent
cannot be taken for granted, and the problem of minimizing error
cannot be dismissed simply because the person seems cooperative.
People may knowingly or unknowingly bias their responses to any
form of subjective report instrument in accordance with their beliefs,
expectations, or personal goals. In addition, the test situation itself,
including the attitudes and behaviors of the health care providers
present, may affect the data obtained. Inaccuracy may result from
distortions in memory as well as from medication toxicity. A brief
description of several biasing factors follows.
Personal Meaning
As discussed in Chapter 8, how people interpret their symptoms and
the meaning attributed to them can have a significant impact on
illness behavior, including the response to treatment. Although not
designed specifically for chronic pain patients, instruments that mea-
sure the personal meaning of life events in terms of purposefulness,
personal control, and self-esteem may be useful to adapt for pain
patients.
The theoretical concept of coherence as defined by Antonovsky
(1980) involves the sense of put pose in life. Crumbaugh's (1968)
Purpose-in-Life Scale asks respondents to indicate how they perceive
their personal existences and the world as meaningful or purposeful
and the extent to which their lives have reasons, purposes, or goals. A
7-point ordinal scale is used; higher scores indicate greater coherence.
Personal control constructs can be assessed with instruments de-
signed to scale "locus of control": the extent to which individuals
believe they versus fate control the major events of their lives. The
Multidimensional Health Locus of Control Scale (Waliston et al.,
1978), for example, assesses the extent to which patients believe in a
cause-effect relationship between their actions and their state of
health. Three separate dimensions of locus of control are assessed: (1)
internality, the extent to which health is perceived to be a function of
one's behavior; (2) powerful others externality, the extent to which the
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MEASURING PEN ED DYSFUNCTION 225
actions of other people are seen as controlling one's health; and (3)
chance externality, the extent to which health or lack of health can be
attributed to fate. The test consists of three six-item scales. Each item
requires a response on a 4-point scale ranging from "strongly agree" to
"strongly disagree."
Patients' beliefs about the perceived cause, nature, and expected
course and ejects of pain can be assessed with Kleinman's (1980)
Explanatory Model method of elicitation. When combined with a few
questions from the Health Belief Model (Rosenstock, 1966) regarding
perceived vulnerability to pain, it could give assessors a quick way of
taking the patient's perspective into account.
Coping
Chronic illness, including chronic pain, may be viewed as a stressor
with which patients must cope (Lipowski, 1971; Lazarus and
DeLongis, 19831. Coping skills are one more of the many factors that
are likely to affect chronicity, functional status, and the seeking of
disability benefits (Strauss, 1975; Thornbury, 19821. Lazarus and
colleagues (Folkman, Schaefer and Lazarus, 1979; Lazarus and
DeLongis, 1983) have offered a cognitive framework for understanding
coping as a process. This model predicts that patients will tend to
change their attitudes toward illness and associated life change
demands over time. Working within this model, Thornbury (1982) and
Moos and Tsu (1977) identified illness-related coping responses and
several cognitive skills that may be used in therapy to teach patients
to cope with extended illness.
Several instruments have been developed to assess coping skills. The
Ways of Coping Check List was derived from Lazarus' transactional
model of stress (Folkman and Lazarus, 1980) and subsequently revised
(VitaTiano et al., 19851. An event is considered stressful when the
patient appraises it as being potentially dangerous to his or her
psychological well-being. Five scales (revised form) can account for
patient coping behaviors: (1) problem-focused coping, (2) wishful
thinking, (3) avoidance, (4) seeks social support, and (5) blames self.
The Coping Scale Questionnaire (Rosentie! and Keefe, 1983) asks
people to rate how often they use certain strategies for coping with
pain. A list of 42 strategies is provided that includes 6 different types
of cognitive strategies and 1 behavioral strategy. Cognitive strategies
include diversion of attention, reinterpretation of pain sensations,
coping self-statements, ignoring pain, praying and hoping, and
catastrophizing. The patient's belief about how much control he or she
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226 ASSESSING ED TREATING PEN kD DYSFUNCTION
has over pain is also recorded. Turner and CIancy (1986) used this
instrument in a study of back pain patients undergoing behavioral
interventions. They replicated the factor structure for the test and
observed that increased praying or hoping was associated with de-
creased pain ratings.
Memory for Pain
The ability of patients to remember pain while in a relatively
pain-free state has been shown to be reasonably accurate up to a week
after surgery (Hunter et al., 1979; Kwilosz et al., 1984~. For pain that
persists, and when measures are being compared over time, research
has demonstrated that current pain intensity produces systematic
distortions of memory for prior pain, independent of treatment out-
come (Etch et al., 19851. This influence of current pain on memory of
past pain in persistent or chronic pain situations suggests that mea-
sures derived from the patient's recollection are probably invalid and
at best likely to be biased.
Attributional Factors
Patients, like people in general, tend to behave in accordance with
their beliefs about the world and themselves. Moreover, behavior is
accommodated to the social environment of the moment in psychiatri-
cally normal persons. The person who believes that he or she has a
serious undetected disease and who is being tested or observed by
health care providers will generally act in accordance with this belief.
Such a patient may unknowingly exaggerate reports of pain and
related problems and will behave as he or she believes a person sick
with a serious disease should. The patient who fears being labeled as
a "psychogenic pain" patient may become theatrical in displaying
suffering and functional impairment in the clinical setting, but when
observed fortuitously in the hospital cafeteria later the same day may
appear quite normal.
The opposite bias may also occur. The driven, time-obsessed execu-
tive who tends to deny disease may fait to report angina or other
relevant symptoms as well as functional problems in an attempt to
evade an illness assignment that would impair his or her personal and
professional lifestyle. Thus, the patient's own beliefs (which may be
shared by other family members) can severely bias the assessment of
pain and pain-related impairment.
Similar biases may affect treatment outcome when pain patients are
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MEASURING PAIN ED DYSFUNCTION 227
subjected to surgery, drug therapy, or psychological interventions.
Most of the literature in this area is concerned with the placebo
effect—the tendency to report favorable outcomes in order to please the
clinician, fulfill the therapeutic hopes of family or self, or achieve some
other goal, such as maintaining employment. However, the opposite
phenomenon also occurs; some patients fad] to report therapeutic
benefit when it probably has occurred. Because both pain reports and
performance on function tests are voluntary efforts, patients' claims of
therapeutic failure cannot be challenged. Such behavior is largely a
matter of patients acting in accordance with their own beliefs about
their health and roles in society and may be consciously or uncon-
sciously motivated. Research on placebo effects has helped to empha-
size the importance of the context of interventions and of the doctor-
patient relationship as determinants of pain report and pain behavior.
Medication Toxicity
Measurement error may also occur when the patient is toxic from
excessive medication. Over months or years of seeking pain relief,
some patients gradually develop toxicity from polypharmacy and
medication overuse. The toxic patient often is irritable, has difficulty
concentrating, is depressive, and may be lethargic (Hall et al., 19801.
The data obtained from such patients are rarely reliable and are of
little value if the purpose of data collection is to evaluate pain or pain
relief. It is best to detoxify such individuals before attempting to
evaluate their pain and its impact.
SUMMARY
Because human pain is an area of inquiry rich in complexity and
multidimensionality, it is of interest to clinical and basic scientists in
a wide variety of fields. It can be studied within several different
conceptual models. From the viewpoint of measurement, however, this
richness is also its great deficiency. The lack of consensus among
investigators on precisely how pain should be defined operationally
and the conceptual tensions that emerge from different interpretations
of related variables such as mood disorders engender confusion and
contradiction.
A number of well-defined instruments are available for assessing
pain and related variables. Each is bound to a theoretical position, and
each has its strengths and weaknesses. None can yield unequivocal
evidence of the presence of painful activity within the nervous system
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228 ASSESSING kD TREATING PEN ED DYSFUNCTION
apart from the patient's report and behaviors. Most experienced
clinicians tend toward the eclectic: Subjective data are used to build a
broad picture of the individual patient. Decisions for diagnosis and
treatment are based on interpretations drawn from patterns evident
among the combined measures. Because pain levels vary so much from
hour to hour and day to day, ideally, such measures would be used
repeatedly in order to have a longitudinal record and to avoid making
inappropriate inferences based on a single assessment.
In recent years measures of functional capability have emerged in
the literature. Pain-related disability has been investigated in several
studies, and it is clear that (1) there is no direct relation between
severity of pain and disability and (2) some disabled pain patients can
be rehabilitated when pain relief is not achieved. These findings
suggest that disability status ought not to be granted on the basis of
pain complaint alone. Evaluation of the candidate for disability status
should include pain assessment, but this should be interpreted in the
context of measures of functional capability in various realms of the
claimant's life.
IMPLICATIONS FOR SSA DISABILITY ASSESSMENT
In light of the preceding review of pain measurement, the committee
agrees with the conclusion of the Pain Commission (U.S. Department
of Health and Human Services, 1987) that there is no direct, objective
way to measure the experience of pain. Because adequate technology
for the objective assessment of chronic pain is not available, the
committee believes that attempts to draw inferences about the
ability of a patient to engage in gainful employment on the basis of
pain measurement are futile. Instead, disability evaluation efforts
should focus on pain-related dysfunction rather than on pain alone.
Both multidimensional pain indices and measures of functional capac-
ity should be obtained so that a comprehensive evaluation is per-
formed.
MEASUREMENT PANELISTS
Fields, Howard L., M.D., Ph.D. Professor of Neurology and Physiology,
University of California, San Francisco
Florence, David W., M.D. Director of Medical Affairs, People's Com-
munity Hospital Authority, Wayne, Michigan
Keefe, Francis, Ph.D. Associate Professor and Director, Pain Manage-
ment Program, Duke University
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MEASURING PAIN AND DYSFUNCTION 229
Marcus-Lewis, Frances, R.N., Ph.D. Professor of Community Health
Care, University of Washington School of Nursing, Seattle
Merskey, Harold, D.M., F.R.C. Psych. Director of Education and
Research, London Psychiatric Hospital, Ontario
Sternbach, Richard A., Ph.D. Director, Pain Treatment Center
Scripps Clinical Medical Group, Inc., La JolIa, California
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Representative terms from entire chapter:
chronic pain
