Multivariable analysis for identification of factors associated with radiographic SIJ progression defined as a change of at least one grade in at least one SIJ and ignoring a change from 0 to 1 over 2 years
| Variable | OR | 95% CI | P value |
| Prior TNFi use up to the start of X-ray interval yes/no | 0.21 | 0.07 to 0.65 | 0.006 |
| Baseline sacroiliac damage (0–7) at start of each X-ray interval | 1.35 | 1.02 to 1.77 | 0.04 |
| Female sex | 0.26 | 0.07 to 0.94 | 0.04 |
| Symptom duration | 1.06 | 1.01 to 1.10 | 0.01 |
| Current smoking | 2.47 | 0.75 to 8.11 | 0.14 |
| HLA-B27 negative | 0.88 | 0.18 to 4.35 | 0.87 |
| NSAID use at start of each X-ray interval | 0.86 | 0.25 to 2.98 | 0.81 |
| ASDAS at start of each X-ray interval | 1.06 | 0.62 to 1.81 | 0.82 |
Analysis in 302 patients and 483 X-ray intervals (22 events).
ASDAS, Ankylosing Spondylitis Disease Activity Score; HLA-B27, human leucocyte antigen B27; NSAID, non-steroidal anti-inflammatory drug; SIJ, sacroiliac joint; TNFi, tumour necrosis factor inhibitor.