Table 4.

Sensitivity analysis for identification of factors associated with radiographic SIJ progression with alternative disease activity parameters

Variable	OR	95% CI	P value
Prior TNFi use up to the start of X-ray interval yes/no	0.22	0.08 to 0.60	0.003
Baseline sacroiliac damage (0–7) at start of each X-ray interval	1.32	1.00 to 1.75	0.047
Female sex	0.27	0.07 to 1.04	0.06
Symptom duration	1.06	1.01 to 1.10	0.01
Current smoking	2.46	0.75 to 8.11	0.14
HLA-B27 negative	0.77	0.16 to 3.83	0.75
NSAID use at start of each X-ray interval	0.90	0.26 to 3.10	0.86
BASDAI at start of each X-ray interval	1.02	0.81 to 1.29	0.88
CRP at start of each X-ray interval	1.01	0.98 to 1.04	0.55

Analysis in 302 patients and 483 X-ray intervals (22 events).

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.