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Defining active sacroiliitis on Magnetic Resonance Imaging (MRI) for classification of axial spondyloarthritis – a consensual approach by the ASAS/ OMERACT MRI Group
  1. Martin Rudwaleit (martin.rudwaleit{at}
  1. Charité University Medicine, Campus Benjamin Franklin, Dept of Rheumatology, Berlin, Germany
    1. Anne-Grethe Jurik (jurik{at}
    1. Aarhus University Hospital, Dept of Radiology, Aarhus, Denmark
      1. Kay-Geert A Hermann (kgh{at}
      1. Charité University Medicine, Charité Campus Mitte, Dept of Radiology, Berlin, Germany
        1. Robert Landewé (r.landewe{at}
        1. University of Maastricht, Dept of Rheumatology, Maastricht, Netherlands
          1. Désirée van der Heijde (d.vanderheijde{at}
          1. Leiden University Medical Center, Dept of Rheumatology, Leiden, Netherlands
            1. Xenofon Baraliakos (baraliakos{at}
            1. Rheumazentrum Ruhrgebiet, Herne, and Ruhr-University, Bochum, Germany
              1. Helena Marzo-Ortega (h.marzo-ortega{at}
              1. University of Leeds, Section of Musculoskeletal Disease, Leeds, United Kingdom
                1. Mikkel Ostergaard (mo{at}
                1. Copenhagen University Hospitals, Dept of Rheumatology, Copenhagen, Denmark
                  1. Jürgen Braun (j.braun{at}
                  1. Rheumazentrum Ruhrgebiet, Dept of Rheumatology, Herne, Germany
                    1. Joachim Sieper (joachim.sieper{at}
                    1. Charité University Medicine, Campus Benjamin Franklin, Dept of Rheumatology, Berlin, Germany


                      Background: Magnetic resonance imaging (MRI) of sacroiliac joints has evolved as the most relevant imaging modality for diagnosis and classification of early axial spondyloarthritis (SpA).

                      Objectives: To identify and describe MRI findings in sacroiliitis, and to reach consensus on which MRI findings are essential for the definition of sacroiliitis.

                      Methods: Ten physicians (2 radiologists and 8 rheumatologists) from the ASAS/ OMERACT MRI working group reviewed and discussed in three workshops MR images depicting sacroiliitis associated with SpA, and other conditions which may mimic SpA. Descriptions of the pathological findings and technical requirements for the appropriate acquisition were formulated. In a consensual approach MRI findings considered to be essential for sacroiliitis were defined.

                      Results: Active inflammatory lesions such as bone marrow edema (BME)/ osteitis, synovitis, enthesitis and capsulitis associated with SpA can be detected by MRI. Among these, the clear presence of BME/ osteitis was considered essential for defining active sacroiliitis. Structural damage lesions such as sclerosis, erosions, fat deposition, and ankylosis can also be detected by MRI. At this moment, however, the exact place of structural damage lesions for diagnosis and classification is less clear, particularly if these findings are minor. The ASAS group formally approved these proposals by voting at the annual assembly.

                      Conclusions: For the first time, MRI findings relevant for sacroiliitis have been defined by consensus by a group of rheumatologists and radiologists. These definitions should help in applying correctly the imaging feature ‘active sacroiliitis by MRI’ in the new ASAS classification criteria for axial SpA.

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