Validation of questionnaire-based response criteria of treatment efficacy in the fibromyalgia (FM) syndrome

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OBJECTIVE: To compare the validity of self-reported questionnaires
as response criteria of treatment efficacy in patients with
fibromyalgia syndrome.

METHOD: At the beginning of the
treatment period, 70 fibromyalgia patients, randomly allocated
to electro-acupuncture or placebo, underwent a clinical
evaluation by rheumatologists and answered 1) a generic
quality of life questionnaire–the Psychological General
Well-Being Index (PGWB), 2) a specific function and symptom
questionnaire, and 3) a pain questionnaire–the Regional Pain
Score (RPS). The same evaluation was repeated at the end of
the treatment period. Severity of the condition was assessed
by a composite outcome score, a combination of different
clinical outcome measures forming a clinical severity index.

The variations between these questionnaire scores before and
after treatment and the variations between the clinical
severity indices estimated by clinicians were used as measures
of the treatment impact. The first rationale for the
validation was a positive correlation between clinical and
questionnaire score changes. Another rationale for validation
of the new instruments was the ability to identify the
different treatment interventions.

RESULTS: The correlation
between the clinical severity index and the RPS was good (r =
0.62). Moreover, the RPS demonstrated a good discriminant
power in detecting patients with effective treatment: it
showed a specificity of 74% and a sensitivity of 75%. The PGWB
correlated less well with the clinical score and was less
discriminant. The specific function and symptom questionnaire
showed little additional validity.

CONCLUSIONS: Outcomes of
syndrome severity such as pain and subjective well-being, as
measured by self-reported questionnaires, can be valid
instruments to evaluate treatment efficacy in short-term
clinical trials. In the current study, the RPS proved to be
particularly useful to assess the widespread tenderness of
fibromyalgia and demonstrated high discriminative power.

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