Table 1: ASAS criteria for axial spondyloarthropathy [9].

Back pain ≥3 months and age <45 years ET Sacroiliitis by MRI or radiography* + 1 other feature OR HLA B27 + 2 other features Features of axial SpA Inflammatory back pain 4 of the 5 following characteristics  Age <40 years  Insidious onset  Improvement with exercise  No improvement with rest  Pain at night Arthritis Past or present active synovitis diagnosed by a physician Enthesitis Pain spontaneously or upon palpation of the Achilles tendon insertion site or plantar fascia Uveitis Past or present anterior uveitis diagnosed by a physician Dactylitis Past or present active dactylitis diagnosed by a physician Psoriasis Past or present active psoriasis diagnosed by a physician Crohn's disease/ulcerative colitis Past or present, diagnosed by a physician Good response to NSAIDs 24–48 h after the initiation of full-dose NSAID therapy, the pain is gone or much better Family history for SpA First- or second-degree relative with any of the following: SpA, psoriasis, acute uveitis, reactive arthritis, chronic inflammatory bowel disease HLA-B27 Presence of B27 Elevated CRP CRP above the upper limit of the normal range, in the absence of another cause of CRP elevation

Sacroiliitis (X-rays or MRI): Definite radiographic sacroiliitis (grade 2 bilaterally or grade 3-4 unilaterally; according to modified New York criteria 1984) Or—active (acute) inflammation of sacroiliac joints on MRI, highly suggestive of sacroiliitis associated with spondyloarthritis.