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This
case illustrates a disorder where measuring more than one symptom
is important. Many medical and psychological disorders are manifested
by more than a single symptom.
- Chronic
lung disease is accompanied by dyspnea, fatigue, cough, and
other symptoms.
- Cancer,
rheumatologic disorders, hypothyroidism and other endocrine
diseases, multiple sclerosis and other neurologic conditions,
depression, anxiety, and numerous other systemic diseases exhibit
a variety of symptoms.
- Functional
syndromes such as irritable bowel syndrome, fibromyalgia, chronic
fatigue syndrome, and migraine headache consist of a constellation
of symptoms.
Besides multiple
symptoms, there are also multiple dimensions of a single
symptom that can be measured (as previously mentioned) including
severity, temporal factors (frequency and duration of episodes),
and functional impairment.
An excellent
example of a multi-symptom, multidimensional instrument is the
Memorial Symptom Assessment Scale, included in Appendix
2 (Portenoy
et al.,1994a).
Table 15.1
below provides a matrix of symptom measures in terms of number
of symptoms evaluated, number of dimensions, and a third characteristic
of the measure -- which symptoms are selected for evaluation.
| Table15.1:
Types of Measures for Evaluating Symptoms
|
|---|
| Number
of Symptoms
| Number
of Dimensions
| Selection
of Symptoms
| Example
Measures
|
|---|
|
One
|
One
|
Fixed
| Visual
analogue or Likert-type pain or other symptom scale |
|
One or Multiple
|
One
|
Patient
| Same
as above, but symptoms are selected by patient. MQOL-PS
|
|
One
|
Multiple
|
Fixed
| Multidimensional
scales for pain; fatigue; dyspnea; dizziness; irritable
bowel syndrome. |
|
Multiple
|
One
|
Fixed
| PHQ-15;
SCL-90 |
|
Multiple
|
Multiple
|
Fixed
| Portenoy
MSAS |
|
Most
measures are developed and validated with a fixed symptom or list
of symptoms. However, there are measures in which the patient
or subject decides which symptom or symptoms are most personally
relevant.
One example
of this patient-specific assessment that we have already provided
is the measure used in Figure
3.2 and Figure 7.1
-- a generic measure which refers to the patient's "symptoms"
(rather than a specific symptom), allowing the patient to rate
whatever symptoms s/he is experiencing. If one is studying a population
with a particular symptom, one could insert the particular symptom
being studied (pain, dizziness, fatigue) for the word "symptoms".
Another measure
in which the relevant symptoms are specific to the patient being
evaluated is the McMaster's Quality of Life - Physical Symptom
subscale (MQOL-PS) (Cohen
et al.,1997; Tierney
et al.,1998). As shown in Figure 15.1 below, the MQOL-PS allows
patients to rate their 3 most bothersome symptoms.
| Figure
15.1: McMaster's Quality of Life Physical Symptom Subscale
|
|---|
|
|
The
MQOL-PS was initially designed for use in palliative care where
individuals may experience multiple symptoms, yet the symptoms
most bothersome may vary from patient to patient.
A patient-centered
scale like the MQOL-PS may be useful in patient follow-up to monitor
the natural history (in an observational study) or therapeutic
responsiveness (in a clinical trial) of the symptoms most relevant
to a particular subject.
Alternatively,
such a scale might be useful in rating adverse consequences of
treatment (e.g. allowing the patient to choose and rate the side
effects most relevant to them). For example, in an antidepressant
trial, side effects such as sexual dysfunction or weight gain
may be more relevant to one patient whereas sedation or gastrointestinal
symptoms may be more important to another.
Scales with
a fixed set of symptoms are useful in that they have typically
been validated in a larger number of subjects and also allow comparison
of the same set of symptoms or dimensions across patients with
the same disorder as well as across different types of disorders
which may share common symptoms. Examples of various types of
symptom measures as well as the supporting references are provided
in Table 15.1 shown earlier.
|