Table 1

Clinical and demographic parameters in patients with peripheral arthritis, enthesitis and/or dactylitis, and age at onset usually ≤45 years* (n=266)

All patients (n=266)SpA (n=176)No SpA (n=90)
Age, mean (SD)34.2 (11.5)32.2 (11.6)38.2 (10.3)
Male gender, %58.663.150.0
Peripheral arthritis at presentation, %86.885.290.0
 Monarthritis, %29.726.735.6
 Oligoarthritis (2–4 joints affected), %35.738.630.0
 Polyarthritis (>4 joints affected) %20.719.323.3
Among patients with peripheral arthritis:
 Predominantly lower limb, %69.575.958.2
 Asymmetric arthritis, %70.069.470.9
 Predominantly lower limb and asymmetric arthritis, %48.550.045.7
 Predominantly lower limb and/or asymmetric arthritis, %86.689.481.3
Enthesitis at presentation, %45.956.824.4
 Enthesitis of the heel, %25.231.313.3
Dactylitis, at presentation, %14.715.313.3
 Uveitis, %
 Psoriasis, %
 IBD, %2.33.40
 Preceding infection, %
IBP in the past but not current (according to local rheumatologist), %12.814.210.0
Family history of SpA (AS, reactive arthritis, uveitis, psoriasis, IBD), %
HLA-B27, %
Elevated CRP (above upper normal limit), %
CRP concentration in mg/litre, mean (SD)2.4 (9.9)2.8 (12.0)1.6 (3.0)
Definite radiographic sacroiliitis (≥grade 2 bilateral or ≥grade 3 unilateral), n (%)§34 (15.0)32 (19.5)2 (3.2)
Active inflammation of sacroiliac (SI) joints (MRI), n (%)22 (36.6)22 (44.0)0 (0)
  • * Age at onset was >45 years in 15% of all patients; these patients were not excluded from the analysis.

  • Global judgement on presence or absence of IBP, independent of formal criteria.

  • Family history of AS, psoriasis, reactive arthritis, uveitis, or IBD in a first-degree relative (father, mother, sisters, brothers, children) or second-degree relative (maternal and paternal grandparents, aunts, uncles, nieces and nephews).

  • § Radiographs were performed in 227 patients (SpA n=164, no SpA n=63). Interpretation of radiographs was done locally. The percentage figures refer to the percentage of patients with definite radiographic sacroiliitis among all those patients who underwent radiographic examination.

  • MRI of the SI joints was performed in 60 patients. Interpretation of MRI was done locally. The percentage figures refer to the percentage of patients with active inflammatory lesions among all those patients who underwent MRI examination.

  • AS, ankylosing spondylitis; CRP, C reactive protein; HLA-B27, human leucocyte antigen B27; IBD, inflammatory bowel disease; IBP, inflammatory back pain; SpA, spondyloarthritis.