The influence of discrepant imaging judgements on the classification of axial spondyloarthritis is limited: a replication in the SpondyloArthritis Caught Early (SPACE) cohort

Sacroiliitis on imaging is important in the diagnosis and classification of patients with axial spondyloarthritis (axSpA). In the Assessment of SpondyloArthritis International Society (ASAS) classification criteria for axSpA, sacroiliitis is defined as either radiographic sacroiliitis (X-SI) according to the modified New York (mNY) criteria or active inflammation on MRI sacroiliac joints (MRI-SI) highly suggestive of axSpA (ASAS definition).1–4 According to the ASAS criteria, patients with chronic back pain are classified via the imaging arm when sacroiliitis on MRI-SI or X-SI plus ≥1 spondyloarthritis (SpA) feature is present, or via the clinical arm where ≥2 SpA features in addition to Human Leukocyte Antigen B27 (HLA-B27) have to be present.While local clinicians can interpret imaging of the sacroiliac joints in the context of clinical information, central readers of research studies …