Sensitivity analysis: integrating a third reading of radiographs for the 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
| Variable | A.TNFi use before the 2-year radiographic interval | B.TNFi use during the 2-year radiographic interval | ||||
| OR | 95% CI | P value | OR | 95% CI | P value | |
| Prior TNFi use up to the start of X-ray interval yes/no | 0.50 | 0.28 to 0.89 | 0.02 | |||
| TNFi use during X-ray interval≥1 year | 0.46 | 0.27 to 0.78 | <0.01 | |||
| TNFi use during X-ray interval<1 year | 0.57 | 0.18 to 1.84 | 0.35 | |||
| Baseline sacroiliac damage at start of each X-ray interval (0–7) | 1.12 | 0.97 to 1.29 | 0.12 | 1.11 | 0.97 to 1.28 | 0.13 |
| Female sex | 0.74 | 0.44 to 1.26 | 0.27 | 0.73 | 0.43 to 1.26 | 0.26 |
| Symptom duration | 1.00 | 0.97 to 1.03 | 0.99 | 1.00 | 0.97 to 1.03 | 0.93 |
| Current smoking | 1.29 | 0.76 to 2.18 | 0.35 | 1.23 | 0.73 to 2.08 | 0.43 |
| HLA-B27 negative | 1.99 | 1.04 to 3.80 | 0.04 | 1.91 | 1.00 to 3.66 | 0.05 |
| NSAID use at start of each X-ray interval | 0.72 | 0.40 to 1.29 | 0.27 | 0.71 | 0.40 to 1.28 | 0.26 |
| ASDAS at start of each X-ray interval | 0.85 | 0.64 to 1.14 | 0.28 | 0.95 | 0.72 to 1.25 | 0.69 |
Three hundred one patients with 477 intervals (87 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.