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Defining active sacroiliitis on MRI for classification of axial spondyloarthritis: update by the ASAS MRI working group
  1. Robert G W Lambert1,
  2. Pauline A C Bakker2,
  3. Désirée van der Heijde2,
  4. Ulrich Weber3,4,
  5. Martin Rudwaleit5,
  6. Kay-Geert A Hermann6,
  7. Joachim Sieper7,
  8. Xenofon Baraliakos8,
  9. Alex Bennett9,
  10. Jürgen Braun8,
  11. Rubén Burgos-Vargas10,
  12. Maxime Dougados11,
  13. Susanne Juhl Pedersen12,13,
  14. Anne Grethe Jurik14,
  15. Walter P Maksymowych15,
  16. Helena Marzo-Ortega16,
  17. Mikkel Østergaard12,13,
  18. Denis Poddubnyy7,
  19. Monique Reijnierse17,
  20. Filip van den Bosch18,
  21. Irene van der Horst-Bruinsma19,
  22. Robert Landewé20
  1. 1Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada
  2. 2Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
  3. 3King Christian 10th Hospital for Rheumatic Diseases, Gråsten, Denmark
  4. 4South Jutland Hospital and Institute of Regional Health Services Research, University of Southern Denmark, Odense, Denmark
  5. 5Endokrinologikum Berlin and Charité University Medicine, Berlin, Germany
  6. 6Department of Radiology, Charité Universitätsmedizin, Berlin, Germany
  7. 7Charité Universitätsmedizin, Berlin, Germany
  8. 8Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum, Herne, Germany
  9. 9Defence Medical Rehabilitation Centre, Surry, UK
  10. 10Department of Rheumatology, Hospital General de México and Faculty of Medicine, Universidad Nacional Autónoma de México, Mexico City, Mexico
  11. 11Department of Rheumatology, Hôpital Cochin, Paris Descartes University, Clinical Epidemiology and Biostatistics, PRES Sorbonne Paris-Cité, Paris, France
  12. 12Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup, Denmark
  13. 13Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
  14. 14Department of Radiology, Aarhus University Hospital, Aarhus, Denmark
  15. 15Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
  16. 16Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds and NIHR Leeds Musculoskeletal Biomedical Research Unit, Leeds Teaching Hospitals NHS Trust, Leeds, UK
  17. 17Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
  18. 18Ghent University Hospital, Ghent, Belgium
  19. 19Department of Rheumatology, VU University Medical Centre, Amsterdam, The Netherlands
  20. 20Amsterdam Rheumatology & Immunology Center, Academic Medical Center, Amsterdam, The Netherlands
  1. Correspondence to Dr Robert G W Lambert, Department of Radiology and Diagnostic Imaging, University of Alberta, 2A2.41 WMC, 8440-112 Street, Edmonton, Alberta, Canada T6G 2B7; rlambert{at}


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
  • Spondyloarthritis
  • 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.