[12][13] Inflammatory back pain tends to come on gradually, become worse at night or after periods of rest (such as in the morning after waking up) and improve after exercise or the use of anti-inflammatory medications such as ibuprofen.

[14] It is recommended that patients be formally evaluated for axial spondyloarthritis if they complain of inflammatory back pain and stiffness lasting at least three months, particularly if they are under the age of 45 and/or have a family history of the disease.

[16][17] Patients being examined for axial spondyloarthritis may have x-rays, or radiographs, taken of their pelvis to check for signs of sacroilitis (often one of the first manifestations of the disease) and structural damage.

[22] Some people with axial spondyloarthritis may test positive for elevated C-reactive protein, or CRP, depending on their disease activity.

[22] Spondyloarthritis is generally considered to be a seronegative disease, meaning tests for rheumatoid factor and other autoantibodies typically come back negative.

[25] Men are more likely to accrue radiographic joint damage, whereas women tend to experience comparatively worse quality of life and disease activity.

[31] One of the central New York criteria was the existence of radiographically visible changes in the sacroiliac joints and/or spine, which have formed due to bone fusion, erosion and/or formation caused by the disease.

[32] Even though these criteria helped to improve uniformly define ankylosing spondylitis, such radiologic changes often only manifested several years after the first disease symptoms appeared.

[2] These included inflammatory back pain, family history for axial spondyloarthritis, response to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs), history of or current inflammation in the joints (arthritis), tendon-bone attachment of the heel (enthesitis), or eyes (uveitis), bowel (inflammatory bowel disease), skin (psoriasis) or signs of elevated inflammation (C-reactive protein and erythrocyte sedimentation rate).

[2][33] The criteria can only be applied in people that have chronic back pain (at least 3 months duration) started before the age of 45 years and only in those patients that already have a diagnosis of axial SpA.