Multivariable analysis for identification of factors associated with radiographic SIJ progression defined as a change in the sacroiliitis sum score over 2 years
| Variable | Estimate | 95% CI |
| Prior TNFi use up to the start of X-ray interval yes/no | −0.118 | −0.203 to −0.033 |
| Baseline sacroiliac damage (0–7) at start of each X-ray interval | −0.017 | −0.041 to 0.207 |
| Female sex | −0.081 | −0.170 to 0.007 |
| Symptom duration | 0.001 | −0.004 to 0.005 |
| Current smoking | 0.087 | 0.001 to 0.173 |
| HLA-B27 negative | 0.084 | −0.038 to 0.207 |
| NSAID use at start of each X-ray interval | −0.018 | −0.112 to 0.077 |
| ASDAS at start of each X-ray interval | 0.011 | −0.034 to 0.056 |
Analysis in 302 patients and 483 X-ray intervals (22 events).
ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; CRP, C-reactive protein; HLA-B27, human leucocyte antigen B27; NSAID, non-steroidal anti-inflammatory drug; SIJ, sacroiliac joint; TNFi, tumour necrosis factor inhibitor.