Systematic review of discriminating power of outcome measures used in clinical trials of fibromyalgia

Objective:Fibromyalgia (FM) comprises many symptoms and features. Consequently, studies on the condition have used a wide variety of outcome measures and assessment instruments. We investigated those outcome measures and instruments in association with the OMERACT (Outcome measures in Rheumatoid Arthritis Clinical Trials) FM Workshop initiative to define core outcome measures that should be used to assess FM.

Methods:A systematic literature review up to December 2007 was carried out using the keywords "fibromyalgia," "treatment" or "management," and "trial." Data were extracted on outcome measures and assessment instruments used and the pre and post mean and standard deviation to calculate effect sizes (ES). Further sensitivity analysis was carried out according to treatment type, blinding status, and study outcome.

Results:The outcome domains identified fell largely within those defined by OMERACT. Morning stiffness was frequently assessed and therefore has been included here. The number of assessment instruments used was wide-ranging, so sensitivity analysis was only carried out on the top 5 within each domain. ES ranged from 0.54 to 3.77 for the key OMERACT domains. Health-related quality of life (HRQOL) was the only exception that had no instrument with moderate sensitivity. Of the secondary domains, dyscognition was lacking any sensitive instrument, as were fatigue and anxiety in pharmacological trials.

Conclusion:Each of the key OMERACT domains has an instrument that appears to be sensitive to change, with the exception of HRQOL, which requires further research. Dyscognition, fatigue, and anxiety would all benefit from more research into their assessment instruments.