Table 3

The effects of TNFi on spinal radiographic progression in mediation analyses

βSE95% CI
Any TNFi use in the current 2-year interval*
 TNF → ASDAS−0.200.09−0.38 to −0.02
 ASDAS → mSASSS progression0.180.080.02 to 0.34
Indirect effect−0.040.03−0.11 to 0.01
Direct effect (TNF → mSASSS progression)−0.050.16−0.37 to 0.28
Total (direct and indirect) effect−0.080.16−0.40 to 0.24
TNFi for ≥12 months in the current 2-year interval*
 TNF → ASDAS−0.360.10−0.57 to −0.16
 ASDAS → mSASSS progression0.170.080.01 to 0.33
Indirect effect−0.060.05−0.18 to 0.01
Direct effect (TNF → mSASSS progression)−0.190.19−0.56 to 0.18
Total (direct and indirect) effect−0.250.19−0.62 to 0.11
Any TNFi use in the previous 2-year interval*
 TNF → ASDAS−0.250.11−0.46 to −0.04
 ASDAS → mSASSS progression0.160.080.00 to 0.33
Indirect effect−0.040.04−0.14 to 0.01
Direct effect (TNF → mSASSS progression)−0.400.19−0.77 to −0.04
Total (direct and indirect) effect−0.450.19−0.81 to −0.08
TNFi for ≥12 months in the previous 2-year interval*
 TNF → ASDAS−0.340.13−0.59 to −0.08
 ASDAS → mSASSS progression0.160.080.00 to 0.32
Indirect effect−0.050.05−0.18 to 0.02
Direct effect (TNF → mSASSS progression)−0.550.23−0.99 to −0.10
Total (direct and indirect) effect−0.600.23−1.05 to −0.15
TNFi for ≥12 months in the previous and
≥12 months in the current 2-year interval*
 TNF → ASDAS−0.270.14−0.55 to 0.01
 ASDAS → mSASSS progression0.170.080.01 to 0.33
Indirect effect−0.040.05−0.17 to 0.02
Direct effect (TNF → mSASSS progression)−0.570.25−1.17 to −0.08
Total (direct and indirect) effect−0.620.25−1.11 to −0.13
  • The table represents the direct, indirect and total effects of TNFi on mSASSS progression in patients with axSpA. These effects are described in the diagram in online supplemental figure S2 in detail.

  • *Parameter estimates from all multivariable models with different TNFi exposure definitions were adjusted for sex, symptom duration at the beginning of the current 2-year interval, smoking in the current 2-year interval, classification as radiographic axSpA, mSASSS at the beginning of the current 2-year interval,and NSAID intake score.

  • ASDAS, Ankylosing Spondylitis Disease Activity Score; axSpA, axial spondyloarthritis; mSASSS, modified Stroke Anlylosing Spondylitis Spine Score; NSAID, non-steroidal anti-inflammatory drugs; SE, standard error; TNFi, tumour necrosis factor alpha inhibitor.