Table 2 Specification of the variables used for the Assessment of SpondyloArthritis international Society (ASAS) criteria for classification of axial spondyloarthritis6
Clinical criterionDefinition
IBPIBP according to experts (see also Box 5): four out of five of the following parameters present: (1) age at onset < 40 years, (2) insidious onset, (3) improvement with exercise, (4) no improvement with rest, (5) pain at night (with improvement upon getting up)
ArthritisPast or present active synovitis diagnosed by a doctor
Family historyPresence in first-degree or second-degree relatives of any of the following: (a) ankylosing spondylitis, (b) psoriasis, (c) uveitis, (d) reactive arthritis, (e) inflammatory bowel disease
PsoriasisPast or present psoriasis diagnosed by a doctor
Inflammatory bowel diseasePast or present Crohn disease or ulcerative colitis diagnosed by a doctor
DactylitisPast or present dactylitis diagnosed by a doctor
EnthesitisHeel enthesitis: past or present spontaneous pain or tenderness at examination at the site of the insertion of the Achilles tendon or plantar fascia at the calcaneus
Uveitis anteriorPast or present uveitis anterior, confirmed by an ophthalmologist
Good response to NSAIDsAt 24–48 h after a full dose of NSAID the back pain is not present anymore or much better
HLA-B27Positive testing according to standard laboratory techniques
Elevated CRPCRP above upper normal limit in the presence of back pain, after exclusion of other causes for elevated CRP concentration
Sacroiliitis by x raysBilateral grade 2–4 or unilateral grade 3–4, according to the modified New York criteria (see Part C, Box 2)
Sacroiliitis by MRIActive inflammatory lesions of sacroiliac joints with definite bone marrow oedema/osteitis suggestive of sacroiliitis associated with spondyloarthritis (see also Part B on MRI)
  • CRP, C-reactive protein; HLA, human leukocyte antigen; IBP, inflammatory back pain; NSAID, non-steroidal anti-inflammatory drug.