Table 4

Impact of time-varying Ankylosing Spondylitis Disease Activity sScore (ASDAS) on spinal radiographic progression

ModelVariableOR 95% CIp Value
6 BASDAI at start of each radiographic interval1.121.00 to 1.260.06
mSASSS at start of each radiographic interval1.071.05 to 1.09<0.001
7 CRP at start of each radiographic interval1.021.01 to 1.040.01
mSASSS at start of each radiographic interval1.081.06 to 1.10<0.001
8 ASDAS at start of each radiographic interval1.391.06 to 1.810.02
mSASSS at start of each radiographic interval1.081.05 to 1.10<0.001
9 TNFi use before radiographic interval yes/no0.610.34 to 1.090.09
ASDAS at start of each radiographic interval1.411.06 to 1.870.02
mSASSS at start of each radiographic interval1.061.04 to 1.09<0.001
Male sex2.141.08 to 4.250.03
Disease duration (5 years)1.130.98 to 1.290.08
Current smoking1.030.57 to 1.850.92
HLA-B271.040.47 to 2.330.92
Number of exercise sessions per week0.950.82 to 1.100.51
Peripheral arthritis0.790.43 to 1.440.43
NSAID use at start of each radiographic interval0.720.35 to 1.480.38
BMI 25–30 (Reference: BMI <25)1.310.73 to 2.360.36
BMI >30 (Reference: BMI <25)1.520.73 to 3.140.26
Duration of radiographic interval1.730.88 to 3.390.11
  • 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.