Table 1.

Classification criteria for axial spondyloarthritis defined by the Assessment of SpondyloArthritis International Society, to be used for patients with back pain for more than 3 mo and an onset of less than 45 years

Sacroiliitis on imaging plus one or more axial spondyloarthritis feature

or

Positive test for HLA-B27 gene plus 2 or more other axial spondyloarthritis features

Sacroiliitis on imaging

Active (acute) inflammation on magnetic resonance imaging highly suggestive of sacroiliitis associated with axial spondyloarthritis

Definite radiographic sacroiliitis according to the modified New York criteria

Axial spondyloarthritis features

Inflammatory back pain Arthritis Enthesitis (heel) Uveitis Dactylitis Psoriasis Crohn’s disease or diagnosis of colitis Good response to non-steroidal anti-inflammatory drugs Family history of axial spondyloarthritis Positive test for HLA-B27 gene Elevated C-reactive protein levels