Professor David Hunter, Florance and Cope Professor of Rheumatology from the University of Sydney

Flare is often used as an outcome or as inclusion criteria in clinical trials of hip and knee osteoarthritis but has not been well defined, according to the Outcome Measures in Rheumatology (OMERACT) initiative.

A systematic review of the literature by the OMERACT Virtual Special Interest Group, found there was an unacceptably wide variation in the definition of osteoarthritis flare. This limits comparison between osteoarthritis trials and interpretation of the evidence.

The Limbic spoke to co-author Professor David Hunter, from the University of Sydney.

What did you find were the essential components in defining OA flare?

The construct of a flare in osteoarthritis has historically centred on pain but honestly, at present is poorly defined. There are a number of other components or features that may contribute to the concept of flare that include effusion, swelling and mobility limitation. This review highlights the lack of a clear definition and underlines the need to develop a tool to measure flare in osteoarthritis.

 How might inconsistency in OA flare definitions skew or devalue the evidence?

In the first instance, the lack of consistency in flare definitions makes comparison between studies incredibly problematic. Furthermore, prior definitions have in large part been based on anecdotal wisdom or expert guidance and have had little if any consumer involvement.

We know that the symptom experience of osteoarthritis is incredibly heterogeneous both between individuals and within an individual, with great fluctuation over time.

Symptom exacerbation is the main source of disability in this disease and it is critical that we develop a greater understanding of it, how to measure it and ultimately how to prevent it. Whilst we continue to rely upon variable definitions we devalue the consumer symptom experience and we limit our own understanding.

 How does rheumatology work towards more consistency in the definition and measurement of OA flares?

With OMERACT we are working with a multinational group to systematically develop a new tool to measure flare in osteoarthritis incorporating consumer involvement and logical item development to best capture consumer experience and expert perspectives.