Developing a standardized definition for disease "flare" in rheumatoid arthritis (OMERACT 9 Special Interest Group)

Traditional outcome measures in randomized controlled trials (RCT) include well-established response criteria as well as ACR EULAR responses using Disease Activity Score 44 (DAS44)/DAS28 to assess improvement; however, a measure to assess worsening of disease has yet to be developed. This special interest group (SIG) was established to develop an evidence-based, consensus-driven standard definition of "flare" in rheumatoid arthritis (RA).

At OMERACT 8, the need for a standardized definition of RA flare was recognized; interested individuals developed a proposal to form a SIG. A literature review was performed to identify publications and abstracts with flare definitions applied in RA, JIA, and lupus RCT as well as concerning patient perspectives on disease worsening. A SIG was held at OMERACT 9 with breakout sessions for patients and investigators.

The RA flare SIG was attended by about 120 participants, including 11 patients. Patients and investigators held separate breakout sessions to discuss various aspects of disease worsening. The following consensus was obtained at OMERACT 9: a working definition of flare should indicate worsening of disease activity (88%), persistence, and duration as critical elements (77%), and consideration of change or increase in therapy (74%).

A working definition of RA flare was developed based on these votes: flare is any worsening of disease activity that would, if persistent, in most cases lead to initiation or change of therapy; and a flare represents a cluster of symptoms of sufficient duration and intensity to require initiation, change, or increase in therapy. Using this working definition, evaluation of candidate domains will be conducted via Delphi exercise and further informed by patient focus groups. Validation of candidate definitions in appropriate RCT will be required.