Objectives To review and update the existing definition of a positive MRI for classification of axial spondyloarthritis (SpA).
Methods The Assessment in SpondyloArthritis International Society (ASAS) MRI working group conducted a consensus exercise to review the definition of a positive MRI for inclusion in the ASAS classification criteria of axial SpA. Existing definitions and new data relevant to the MRI diagnosis and classification of sacroiliitis and spondylitis in axial SpA, published since the ASAS definition first appeared in print in 2009, were reviewed and discussed. The precise wording of the existing definition was examined in detail and the data and a draft proposal were presented to and voted on by the ASAS membership.
Results The clear presence of bone marrow oedema on MRI in subchondral bone is still considered to be the defining observation that determines the presence of active sacroiliitis. Structural damage lesions seen on MRI may contribute to a decision by the observer that inflammatory lesions are genuinely due to SpA but are not required to meet the definition. The existing definition was clarified adding guidelines and images to assist in the application of the definition.
Conclusion The definition of a positive MRI for classification of axial SpA should continue to primarily depend on the imaging features of ‘active sacroiliitis’ until more data are available regarding MRI features of structural damage in the sacroiliac joint and MRI features in the spine and their utility when used for classification purposes.
- Magnetic Resonance Imaging
- Ankylosing Spondylitis
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Handling editor Tore K Kvien
Contributors All authors substantially contributed to the conception and/or design of the work, and the interpretation of data; drafting the work and/or revising it critically for important intellectual content; have final approval of the version published; and agree to be accountable for all aspects of the work.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.