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

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 questionaire-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.