Original data and data with IPTW
| Covariates | Original data | Data with IPTW | ||||
| Off the TNFis | On the TNFis | SMD | Off the TNFis | On the TNFis | SMD | |
| Age, mean (SD), year | 32.66 (8.80) | 32.74 (8.80) | 0.009 | 33.25 (9.23) | 33.03 (8.97) | 0.024 |
| Female (%) | 101 (10.6) | 120 (10.7) | 0.004 | 88.2 (10.5) | 107.0 (10.8) | 0.011 |
| Eye involvement (%) | 468 (49.0) | 549 (48.8) | 0.002 | 447.6 (53.2) | 506.7 (51.3) | 0.038 |
| Peripheral joint involvement (%) | 540 (56.5) | 630 (56.0) | 0.009 | 511.4 (60.8) | 583.5 (59.1) | 0.035 |
| ESR at the start of the interval, mean (SD), log | 2.30 (1.07) | 2.52 (1.17) | 0.190 | 2.42 (1.14) | 2.51 (1.19) | 0.071 |
| CRP at the start of the interval, mean (SD), log | 0.02 (0.47) | 0.17 (0.64) | 0.276 | 0.14 (0.62) | 0.19 (0.66) | 0.083 |
| BASDAI at the start of the interval, mean (SD), square root | 1.60 (0.57) | 1.84 (0.72) | 0.365 | 1.72 (0.63) | 1.82 (0.74) | 0.144 |
| mSASSS at the start of the interval, mean (SD) | 20.00 (20.07) | 19.43 (19.96) | 0.028 | 20.98 (20.14) | 20.17 (20.32) | 0.040 |
| cDMARDs* (%) | 27 (2.8) | 56 (5.0) | 0.112 | 42.2 (5.0) | 53.6 (5.4) | 0.019 |
| NSAIDs* (%) | 101 (10.6) | 307 (27.3) | 0.438 | 160.4 (19.1) | 206.3 (20.9) | 0.046 |
| *Glucocorticoids (%) | 16 (1.7) | 17 (1.5) | 0.013 | 35.6 (4.2) | 16.3 (1.7) | 0.153 |
*Number of patients prescribed with drugs for >50% of the interval period.
BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; cDMARDs, conventional disease-modifying anti-rheumatic drugs; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; IPTW, inverse probability of treatment weighting; mSASSS, modified Stoke Ankylosing Spondylitis Spinal Score; NSAIDs, non-steroidal anti-inflammatory drugs mSASSS change per year with and without TNFi therapy; SMD, standardised mean difference; TNFis, tumour necrosis factor inhibitors.