Table 3.

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.