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

Back pain ≥3 months and age <45 years ET
Sacroiliitis by MRI or radiography* + 1 other featureORHLA B27 + 2 other features

Features of axial SpA
Inflammatory back pain4 of the 5 following characteristics
 Age <40 years
 Insidious onset
 Improvement with exercise
 No improvement with rest
 Pain at night
ArthritisPast or present active synovitis diagnosed by a physician
EnthesitisPain spontaneously or upon palpation of the Achilles tendon insertion site or plantar fascia
UveitisPast or present anterior uveitis diagnosed by a physician
DactylitisPast or present active dactylitis diagnosed by a physician
PsoriasisPast or present active psoriasis diagnosed by a physician
Crohn's disease/ulcerative colitisPast or present, diagnosed by a physician
Good response to NSAIDs24–48 h after the initiation of full-dose NSAID therapy, the pain is gone or much better
Family history for SpAFirst- or second-degree relative with any of the following: SpA, psoriasis, acute uveitis, reactive arthritis, chronic inflammatory bowel disease
HLA-B27Presence of B27
Elevated CRPCRP 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.