Table 1

Baseline characteristics of patients with baseline and follow-up pelvic radiographs

Patients with paired radiographs (N=357)
Age, years (mean, SD)33.8 (10.8)
Age at onset of back pain, years (mean, SD)26.2 (8.8)
Male gender, n (%)171 (47.9)
Number of SpA features* (mean, SD)2.5 (1.4)
Definite radiographic sacroiliitis (mNY), n (%)62 (17.4)
Active inflammation of SIJ†, MRI, n (%) (n=223)112 (50.2)
HLA-B27 positivity, n (%)174 (48.7)
Elevated CRP, n (%)135 (37.8)
IBP (according to experts’ definition), n (%)178 (49.9)
Peripheral arthritis past or present, n (%)193 (54.1)
Heel enthesitis past or present, n (%)79 (22.1)
Uveitis past or present, n (%)32 (9.0)
Dactylitis past or present, n (%)39 (10.9)
Psoriasis past or present, n (%)27 (7.6)
IBD past or present, n (%)14 (3.9)
Good response to NSAIDs, n (%)126 (35.4)
Family history of SpA, n (%)79 (22.1)
Preceding infection, n (%)11 (3.1)
Schober's test (cm), mean (SD) (n=354)4.4 (2.5)
Chest expansion (cm), mean (SD) (n=351)5.6 (5.7)
Active inflammation of the spine†, MRI, n (%) (n=110)29 (26.4)
  • *Features included IBP, arthritis, heel enthesitis, dactylitis, uveitis, psoriasis, IBD, good response to NSAIDs, family history of spondyloarthritis and elevated CRP.

  • †Presence or absence of typical signs of active inflammation independent of formal criteria.

  • CRP, C reactive protein; IBD, inflammatory bowel disease; IBP, inflammatory back pain; mNY, modified New York criteria; NSAID, non-steroidal anti-inflammatory drug; SIJ, sacroiliac joints; SpA, spondyloarthritis.