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Many
of the measures described above and referenced in Table 15.1 not
only measure symptom status at baseline but presumably can also
be used at follow-up intervals to detect whether improvement or
worsening has occurred. However, sensitivity to change
is a distinct psychometric characteristic that not all symptom
or other health status instruments or measures possess; it is
something that has to be demonstrated in outcome studies.
A generic
scale developed by Guyatt and used in multidimensional cardiac
and pulmonary disease questionnaires (Guyatt
et al., 1993; Redelmeier
et al.,1996) is shown in Figure 16.1 below.
| Figure
16.1: Global Rating of Change Scale
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Overall,
has there been any change in your symptoms since you
started the new medicine? Please indicate if there
has been any change in your symptoms by choosing one
of the following options. Are your symptoms:
WORSE
ABOUT THE SAME
BETTER
[Patients who state they are better are then asked:]
How much better are your symptoms? Are they:
- ALMOST
THE SAME, HARDLY ANY BETTER AT ALL
- A
LITTLE BETTER
- SOMEWHAT
BETTER
- MODERATELY
BETTER
- A
GOOD DEAL BETTER
- A
GREAT DEAL BETTER
- A
VERY GREAT DEAL BETTER
[Patients who state they are worse are asked how much
worse, and offered similar response options, the word
"worse" being substituted for "better"]
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This
global rating of change measure is essentially a single-item 15-point
scale because a subject may either show:
- No change;
- Improvement
along a 7-point scale; or
- Worsening
along a 7-point scale.
A researcher
studying specific symptoms could substitute the name of the symptom
in place of the word "symptoms", and use this global
change rating scale as one of the outcome measures. Where other
disease-specific or symptom-specific measures are available, they
might be used to complement and enrich the data gathered by this
single-item global change rating scale.
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