Table 4 Definitions of parameters applied in the Assessment of Spondyloarthritis International Society classification criteria for axial and peripheral spondyloarthritis

IBP

According to experts (14): ≥4 out of 5 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)

IBP in the past according to the rheumatologist’s judgment.

In patients with current IBP (and concomitant peripheral manifestations), the ASAS classification criteria for axial SpA should be applied

Arthritis

Past or present active synovitis diagnosed by a physician

Current peripheral arthritis compatible with SpA (usually asymmetric and/or predominant involvement of the lower limbs), diagnosed clinically by a doctor

Enthesitis

Heel enthesitis: past or present spontaneous pain or tenderness at examination of the site of the insertion of the Achilles tendon or plantar fascia at the calcaneus.

Enthesitis: past or present spontaneous pain or tenderness at examination of an entheses.

Any site of enthesitis can be affected whereas in the ASAS classification criteria for axial SpA only enthesitis of the heel is considered.

Uveitis

Past or present uveitis anterior, confirmed by an ophthalmologist

Dactylitis

Past or present dactylitis, diagnosed by a physician

Psoriasis

Past or present psoriasis, diagnosed by a physician

IBD

Past or present Crohn’s disease or ulcerative colitis diagnosed by a physician

Good response to NSAIDs

24–48 h after a full dose of a NSAID the back pain is not present any more or is much better

Not mentioned

Family history of SpA

Presence in first-degree (mother, father, sisters, brothers, children) or second-degree (maternal and paternal grandparents, aunts, uncles, nieces and nephews) relatives of any of the following: (1) AS; (2) psoriasis; (3) acute uveitis; (4) reactive arthritis; (5) IBD

Elevated CRP

CRP concentration above upper normal limit in the presence of back pain, after exclusion of other causes for elevated CRP concentration.

Not mentioned

HLA-B27

Positive testing according to standard laboratory techniques

Radiographic SI

Bilateral grade 2–4 or unilateral grade 3–4 sacroiliitis on plain radiographs, according to the modified New York criteria ref. [3]

SI by MRI

Active inflammatory lesions of sacroiliac joints with definite bone marrow edema/osteitis, suggestive of sacroiliitis associated with SpA

Preceding infection

NA

Urethritis/cervicitis or diarrhoea within 1 month before the onset of arthritis/enthesitis/dactylitis