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  • Review Article
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Diagnosis and classification in spondyloarthritis: identifying a chameleon

Abstract

Spondyloarthritis (SpA) defines a group of interrelated diseases, including ankylosing spondylitis (AS), psoriatic arthritis, reactive arthritis, enteropathic-related spondylitis and arthritis, and undifferentiated SpA. The clinical presentation of SpA is heterogeneous, and no single shared distinguishing feature exists for the conditions comprising SpA; in daily practice, diagnosis is usually made on the basis of a combination of symptoms, the findings of physical examination, imaging and laboratory investigations. Several classification criteria have been developed for AS and SpA, which are useful in a research setting but cannot be automatically applied to the diagnosis of individual patients. Currently, MRI is the most sensitive imaging modality available for detection of sacroiliitis, often enabling detection of axial inflammation long before structural lesions are observed radiographically, thus facilitating early diagnosis of axial SpA. However, MRI will never capture all facets of SpA and the expert opinion of a rheumatologist will remain the crucial step in recognition of this disease. In this Review, we discuss diagnosis and classification of AS and SpA, and highlight how MRI might facilitate both processes.

Key Points

  • Classification criteria designed for high specificity are of limited utility when making a diagnosis in daily practice, as they lack sensitivity at early stages of disease

  • The Assessment of SpondyloArthritis international Society (ASAS) axial spondyloarthritis (axSpA) criteria enable comparisons across trials in early nonradiographic disease, for which new disease-modifying treatment strategies are urgently needed

  • Ongoing research will determine whether the ASAS axSpA classification criteria could contribute to a reduction in the delayed diagnosis of axSpA

  • Although pelvic radiographs, MRI of the axial skeleton and HLA-B27 testing are important for disease classification, negative findings for these assessments do not preclude a diagnosis of axSpA

  • MRI enables detection of axial inflammation in early SpA long before structural lesions can be visualized on radiographs

  • A data-driven definition of what constitutes a positive MRI finding in axSpA has top priority on the research agenda

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Figure 1: Sacroiliitis in a patient with axSpA as observed on a pelvic radiograph and on SIJ MRI images.
Figure 2: Spinal MRI can identify SpA-associated inflammation.

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Acknowledgements

The authors thank Christian Streng, Head of Medical Documentation, Balgrist University Hospital, Zürich, Switzerland, for technical assistance with Figures 1 and 2. The work of U. Weber is supported by funding from the Foundation for Scientific Research at the University of Zurich and the Walter L. and Johanna Wolf Foundation, Zurich.

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Correspondence to Astrid van Tubergen.

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A. van Tubergen has received Speaker's bureau (honoraria) from Abbott Laboratories, Actelion Pharmaceuticals and MSD, and grant/research support from Abbott Laboratories, MSD, Pfizer and Roche. U. Weber has received Speaker's bureau (honoraria) from Abbott Laboratories.

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van Tubergen, A., Weber, U. Diagnosis and classification in spondyloarthritis: identifying a chameleon. Nat Rev Rheumatol 8, 253–261 (2012). https://doi.org/10.1038/nrrheum.2012.33

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