Model | Variable | OR | 95% CI | p Value |
6 | BASDAI at start of each radiographic interval | 1.12 | 1.00 to 1.26 | 0.06 |
mSASSS at start of each radiographic interval | 1.07 | 1.05 to 1.09 | <0.001 | |
7 | CRP at start of each radiographic interval | 1.02 | 1.01 to 1.04 | 0.01 |
mSASSS at start of each radiographic interval | 1.08 | 1.06 to 1.10 | <0.001 | |
8 | ASDAS at start of each radiographic interval | 1.39 | 1.06 to 1.81 | 0.02 |
mSASSS at start of each radiographic interval | 1.08 | 1.05 to 1.10 | <0.001 | |
9 | TNFi use before radiographic interval yes/no | 0.61 | 0.34 to 1.09 | 0.09 |
ASDAS at start of each radiographic interval | 1.41 | 1.06 to 1.87 | 0.02 | |
mSASSS at start of each radiographic interval | 1.06 | 1.04 to 1.09 | <0.001 | |
Male sex | 2.14 | 1.08 to 4.25 | 0.03 | |
Disease duration (5 years) | 1.13 | 0.98 to 1.29 | 0.08 | |
Current smoking | 1.03 | 0.57 to 1.85 | 0.92 | |
HLA-B27 | 1.04 | 0.47 to 2.33 | 0.92 | |
Number of exercise sessions per week | 0.95 | 0.82 to 1.10 | 0.51 | |
Peripheral arthritis | 0.79 | 0.43 to 1.44 | 0.43 | |
NSAID use at start of each radiographic interval | 0.72 | 0.35 to 1.48 | 0.38 | |
BMI 25–30 (Reference: BMI <25) | 1.31 | 0.73 to 2.36 | 0.36 | |
BMI >30 (Reference: BMI <25) | 1.52 | 0.73 to 3.14 | 0.26 | |
Duration of radiographic interval | 1.73 | 0.88 to 3.39 | 0.11 |
Radiographic spinal progression defined as an increase in mSASSS ≥2 units. Models 6–8 correspond to GEE models for probability of progression, with different disease activity measures and mSASSS at start of each radiographic interval. Model 9 corresponds to the multivariable model used in figure 1A with the additional incorporation of ASDAS at baseline of each individual radiographic interval as a covariate in order to investigate the direct effect of TNFi on spinal radiographic progression (616 radiographic intervals from 432 patients).
ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BMI, body mass index; CRP, C reactive protein; GEE, generalised estimating equation; HLA-B27, human leucocyte antigen B27; mSASSS, modified Stoke Ankylosing Spondylitis Spine Score; NSAID, non-steroidal anti-inflammatory drug; TNFi, tumour necrosis factor inhibitor.