Assessment of different instruments used as outcome measures in patients with fibromyalgia

Objective: To assess the different measure instruments used for patients with fibromyalgia. Patients and methods: This study assessed 60 individuals participating in a clinical trial of cross-sectional cohort comparing the effects of exercises performed in water and on land. The following instruments were used: the Fibromyalgia Impact Questionnaire (FIQ) to assess the impact of the disease; the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36) to assess quality of life; the Beck Depression Inventory to assess depression; and the Visual Analogue Scale (VAS) of pain. Those questionnaires were compared with the results obtained in a transitional Likert-type scale, the verbal scale for assessing change (VSAC), considered as a criterion of change in the assessment of other instruments. Results: The Spearman coefficient was used to study the correlation between the VSAC measure and the other instruments at two occasions (T1 and T2). At T1, a moderate correlation was observed between VSAC and VAS (r = 0.49), and between VSAC and FIQ (r = 0.41), and a negative correlation was observed between VSAC and the SF-36 domains pain (r = -0.49) and general health perception (r = -0.55), and the SF-36 physical component (r = -0.42). At T2, only the SF-36 domain vitality showed a weak negative correlation with VSAC (r = -0.27). Conclusion: Considering VSAC as gold standard, none of the instruments assessed could optimally identify a change in the health status of patients with fibromyalgia.