For years, X-rays have been the standard first imaging test for people being evaluated for axial spondyloarthritis (axSpA). New recommendations presented at the 2026 European Alliance of Associations for Rheumatology (EULAR) Congress suggest that MRI of the sacroiliac (SI) joints should now be used first instead. Researchers say MRI is better able to detect both inflammation and structural damage related to the disease.
The Assessment of SpondyloArthritis International Society (ASAS) and the Spondyloarthritis Research and Treatment Network (SPARTAN) developed the new classification criteria and presented them at the EULAR Congress, which was held in London, England, from June 11–14. The revisions were based on data from the Classification of Axial Spondyloarthritis Inception Cohort (CLASSIC) study. This large international study included more than 1,000 people with chronic back pain who were being evaluated for possible axSpA.
The proposed criteria are the first major update to the ASAS classification criteria since 2009. Researchers sought to improve the accuracy of the criteria while preserving their ability to identify the disease early. Among all of the clinical, laboratory, and imaging features evaluated, MRI evidence of inflammation and structural changes in the SI joints emerged as the strongest predictor of an axSpA diagnosis.
MRI is now recommended as the preferred first imaging test. If MRI is unavailable or cannot be performed, radiography or low-dose CT may be used instead. The recommendations also encourage clinicians to look for structural damage alongside active inflammation when reviewing imaging results.
Other features included in the revised criteria are HLA-B27 positivity, elevated C-reactive protein (CRP), inflammatory back pain, acute anterior uveitis, inflammatory bowel disease, psoriasis, and heel enthesitis. In validation testing, the proposed criteria achieved a sensitivity of 79.5% and a specificity of 90.4%, indicating a strong ability to distinguish axSpA from other causes of chronic back pain.
Together, these updates reflect a growing emphasis on MRI in the assessment of axial spondyloarthritis and may help improve the accuracy and timeliness of diagnosis.
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