Patient characteristics
| SpA subset | n=32 | Age (y) mean (SD) | HLA B27+ (%) | Male (%) | Mean (SD) disease duration (y) | Back pain (VAS 0-10) | MRI: % active SI | Histology cells/mm2 |
| AS | 18 | 34.9 (10.6) | 89 | 75 | 6.8 (4.2) | 8.8 (1.4) | 67 | 6.1 (7.8) |
| uSpA | 12 | 21.8 (5.7) | 83 | 67 | 2.6 (3.6) | 8.4 (1.4) | 100 | 25.0 (30.6) |
| PsA | 2 | 41.2 (13.1) | 100 | 50 | 3.6 (4.8) | 8.0 (0) | 100 | 11.2 (12.5) |
SpA = spondyloarthropathy, AS = ankylosing spondylitis, USpA = undifferentiated SpA, PsA = psoriatic arthritis.