Increasing research interest and emerging new therapies for treatment of fibromyalgia (FM) have led to a need to develop a consensus on a core set of outcome measures that should be assessed and reported in all clinical trials, to facilitate interpretation of the data and understanding of the disease. This aligns with the key objective of the Outcome Measures in Rheumatology (OMERACT) initiative to improve outcome measurement through a data driven, interactive consensus process. Through patient focus groups and Delphi processes, working groups at previous OMERACT meetings identified potential domains to be included in the core data set. A systematic review has shown that instruments measuring these domains are available and at least moderately sensitive to change. Most of instruments have been validated in multiple languages. This pooled analysis study aims to develop the core data set by analysing data from 10 randomised controlled trials (RCTs) in FM. Results from this study provide support for the inclusion of the following in the core data set: pain, tenderness, fatigue, sleep, patient global assessment and multi-dimensional function/health related quality of life. Construct validity was demonstrated with outcome instruments showing convergent and divergent validity. Content and criterion validity were confirmed by multivariate analysis showing R square values between 0.4 and 0.6. Low R square value is associated with studies in which one or more domains were not assessed. The core data set was supported by high consensus among attendees at OMERACT 9. Establishing an international standard for RCTs in FM should facilitate future meta-analyses and indirect comparisons.
Keywords: Fibromyalgia, OMERACT, outcome measures, clinical trials, core data set