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.