Impact of pretreatment Ankylosing Spondylitis Disease Activity Score (ASDAS) on spinal radiographic progression
| Variable | OR | 95% CI | p Value |
| TNFi use before radiographic interval yes/no | 0.52 | 0.29 to 0.92 | 0.02 |
| ASDAS at start of TNFi and ASDAS at inclusion for non-treated patients | 1.33 | 1.00 to 1.78 | 0.05 |
| mSASSS at start of each radiographic interval | 1.07 | 1.04 to 1.09 | <0.001 |
| Male sex | 2.10 | 1.07 to 4.12 | 0.03 |
| Disease duration (5 years) | 1.13 | 0.99 to 1.29 | 0.07 |
| Current smoking | 1.04 | 0.59 to 1.86 | 0.88 |
| HLA-B27 | 1.03 | 0.46 to 2.29 | 0.94 |
| Number of exercise sessions per week | 0.95 | 0.82 to 1.10 | 0.47 |
| Peripheral arthritis | 0.87 | 0.48 to 1.60 | 0.66 |
| NSAID use at start of each radiographic interval | 0.83 | 0.41 to 1.68 | 0.60 |
| BMI 25–30 (Reference: BMI <25) | 1.39 | 0.77 to 2.49 | 0.27 |
| BMI >30 (Reference: BMI <25) | 1.66 | 0.81 to 3.39 | 0.16 |
| Duration of radiographic interval | 1.66 | 0.85 to 3.23 | 0.14 |
Radiographic spinal progression defined as an increase in mSASSS ≥2 units. The model corresponds to the multivariable model used in figure 1A with the additional incorporation of pretreatment ASDAS in TNFi-treated patients as a covariate in order to account for confounding by indication. The ASDAS at inclusion was considered for non-TNFi-treated patients (616 radiographic intervals from 432 patients after multiple imputation of missing covariate data).
ASDAS, Ankylosing Spondylitis Disease Activity Score; BMI, body mass index; HLA-B27, human leucocyte antigen B27; mSASSS, modified Stoke Ankylosing Spondylitis Spine Score; NSAID, non-steroidal anti-inflammatory drug; TNFi, tumour necrosis factor inhibitor.