Definition of SpA features for use of ASAS classification criteria for peripheral SpA
| SpA feature | Definition |
|---|---|
| Entry criteria: | |
| Arthritis | Current peripheral arthritis compatible with SpA (usually asymmetric and/or predominant involvement of the lower limb), diagnosed clinically by a doctor |
| Enthesitis | Current enthesitis, diagnosed clinically by a doctor |
| Dactylitis | Current dactylitis, diagnosed clinically by a doctor |
| Additional SpA features: | |
| IBP in the past* | IBP in the past according to the rheumatologist's judgement |
| Arthritis | Past or present peripheral arthritis compatible with SpA (usually asymmetric and/or predominant involvement of the lower limb), diagnosed clinically by a doctor |
| Enthesitis† | Enthesitis: past or present spontaneous pain or tenderness at examination of an enthesis |
| Uveitis | Past or present uveitis anterior, confirmed by an ophthalmologist |
| Dactylitis | Past or present dactylitis, diagnosed by a doctor |
| Psoriasis | Past or present psoriasis, diagnosed by a doctor |
| IBD | Past or present Crohn's disease or ulcerative colitis diagnosed by a doctor |
| Preceding infection | Urethritis/cervicitis or diarrhoea within 1 month before the onset of arthritis/enthesitis/dactylitis. |
| Family history for 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) ankylosing spondylitis, (2) psoriasis, (3) acute uveitis, (4) reactive arthritis, (5) IBD |
| HLA-B27 | Positive testing according to standard laboratory techniques |
| Sacroiliitis by imaging | Bilateral grade 2–4 or unilateral grade 3–4 sacroiliitis on plain radiographs, according to the modified New York criteria,3or active sacroiliitis on MRI according to the ASAS consensus definition9 |
↵* Here, only IBP in the past is considered. In patients with current IBP (and concomitant peripheral manifestations), the ASAS classification criteria for axial SpA should be applied.6In the ASAS classification criteria for axial SpA, current IBP was considered and defined according to the ASAS experts definition10: at least four out of five 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).
↵† Any site of enthesitis can be affected whereas in the ASAS classification criteria for axial SpA6 only enthesitis of the heel is considered.
ASAS, Assessment of SpondyloArthritis international Society; HLA-B27, human leucocyte antigen B27; IBD, inflammatory bowel disease; IBP, inflammatory back pain; SpA, spondyloarthritis.