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would be easily translated for non-English-speaking patients; and
(e) would capture not only pain severity, but also the perception
of how pain interfered with daily life.
Test Construction Standards
As a guide to scale construction, we used then-current
psychometric standards found in the Standards for Educational
and Psychological Tests published by the American Psychological
Association, American Educational Research Association, and the
National Council on Measurement in Education (1974). These
standards included common elements of test validity (content,
criterion, and construct) and reliability (internal consistency and
test-retest). These standards had not been systematically applied
in the development of the existing pain report scales.
Measurement Conceptualization: Multiple Dimensions of Pain
That pain is multidimensional was made clear during our patient
interviews: patients reported that an adequate representation of
pain required more than one simple measure of pain intensity.
Melzack and Casey (1968) suggested that, based on the
underlying neurophysiological mechanisms of pain, pain
assessment should include three dimensions: sensory-
discriminative, motivational-affective, and cognitive-evaluative.
This approach to self-report measurement relied on three distinct
patterns of responses to the words that patients used to describe
their pain. However, the patients we interviewed had difficulty
discriminating between the motivational-affective and cognitive-
evaluative dimensions (Cleeland, 1989; Cleeland, 1990).
More commonly, researchers have found that two dimensions of
pain self-report account for most of the variability in the way
patients describe pain. Beecher (1959) called these dimensions
“pain” and “reaction to pain”; Clark and Yang (1983) called them
“sensory-discriminative” and “attitudinal.” Following Beecher, we
called these dimensions “sensory” and “reactive” (Cleeland,
1989).
Accordingly, our new questionnaire was developed to include
items that reported the “sensory” dimension of pain (intensity, or
severity) and the “reactive” dimension of pain (interference with
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daily function). We constructed four items to capture the variability
of pain over time: pain at its “worst,” “least,” “average,” and
“now” (current pain). On the basis of patient interviews from
additional field testing, we chose seven items that measured how
much pain interfered with various daily activities, including general
activity, walking, work, mood, enjoyment of life, relations with
others, and sleep. Two subdimensions of pain interference were
proposed: an affective subdimension (REM: relations with others,
enjoyment of life, and mood) and an activity subdimension (WAW:
walking, general activity, and work). The appropriate
categorization of sleep within these two subdimensions was
unclear.
A graphic representation of the conceptual framework for our
measurement model is shown below. The model conforms to the
U.S. Food and Drug Administration’s Draft Guidance for Industry,
Patient-reported Outcome Measures: Use in Medical Product
Development to Support Labeling Claims (Food and Drug
Administration, 2006).
REM
WAW
Interference
Pain Severity
Working
GeneralActivity
Walking
Mood
Enjoyment of Life
Relations with Others
Pain Now
Average Pain
Least Pain
Worst Pain
Patient Pain Experience
Sleep?
CONSTRUCTS ITEMS