Table 1.
Baseline characteristics at first radiograph
| Parameter | All patients N=515 |
Patients with the potential of SIJ progression (mean SSS≤7) N=415 |
Patients with complete data in multivariable analyses N=302 |
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| Male sex, N (%) | 515 | 341 (66.2) | 415 | 258 (62.2) | 302 | 184 (60.9) |
| HLA-B27 positive, N (%) | 478 | 388 (81.2) | 387 | 308 (79.6) | 302 | 243 (80.5) |
| nr-axSpA, N (%) | 515 | 238 (46.2) | 415 | 238 (57.4) | 302 | 174 (57.6) |
| Age, years | 515 | 40.5 (10.9) | 415 | 39.6 (10.6) | 302 | 39.2 (10.6) |
| Symptom duration, years | 512 | 14.2 (10.6) | 414 | 12.4 (9.8) | 302 | 12.8 (9.5) |
| BASDAI | 439 | 4.1 (2.3) | 351 | 4.1 (2.2) | 302 | 4.1 (2.2) |
| ASDAS | 410 | 2.7 (1.1) | 328 | 2.7 (1.0) | 302 | 2.6 (1.0) |
| CRP, mg/L | 444 | 9.8 (14.8) | 358 | 8.7 (13.6) | 302 | 8.7 (14.0) |
| BASFI | 440 | 2.8 (2.4) | 353 | 2.6 (2.4) | 302 | 2.6 (2.3) |
| BASMI | 458 | 2.0 (2.0) | 370 | 1.5 (1.6) | 300 | 1.5 (1.5) |
| Current enthesitis, N (%) | 463 | 205 (44.3) | 374 | 172 (46.0) | 297 | 135 (45.5) |
| BMI 25–30, % | 465 | 151 (32.5) | 372 | 120 (32.3) | 283 | 90 (31.8) |
| BMI>30, % | 465 | 74 (15.9) | 372 | 61 (16.4) | 283 | 46 (16.2) |
| On NSAID treatment, N (%) | 463 | 364 (78.6) | 376 | 296 (78.7) | 302 | 235 (77.8) |
| On csDMARD treatment, N (%) | 515 | 62 (12.0) | 415 | 47 (11.3) | 302 | 31 (10.3) |
| On TNFi treatment, N (%) | 515 | 235 (45.6) | 415 | 181 (43.6) | 302 | 121 (40.1) |
| Years of TNFi treatment in treated patients | 235 | 2.6 (2.3) | 181 | 2.5 (2.2) | 121 | 2.8 (2.3) |
| Current smokers, N (%) | 466 | 169 (36.3) | 375 | 136 (36.3) | 302 | 110 (36.4) |
| Patients with different number of radiographic intervals*, N (%) | 515 | 415 | 302 | |||
| 1 interval | 288 (55.9) | 231 (55.7) | 182 (60.3) | |||
| 2 intervals | 126 (24.5) | 108 (26.0) | 75 (24.8) | |||
| 3 intervals | 63 (12.2) | 47 (11.3) | 31 (10.3) | |||
| 4 intervals | 28 (5.4) | 22 (5.3) | 12 (4.0) | |||
| 5 intervals | 7 (1.4) | 6 (1.4) | 2 (0.7) | |||
| 6 intervals | 3 (0.6) | 1 (0.2) | 0 (0.0) | |||
Except where indicated otherwise, values are the mean (SD).
ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Metrology Index; BMI, Body Mass Index; CRP, C-reactive protein (CRP) levels; csDMARD, conventional synthetic disease-modifying antirheumatic drug; HLA-B27, human leucocyte antigen B27; mSASSS, modified Stoke Ankylosing Spondylitis Spine Score; nr-axSpA, nonradiographic axial spondyloarthritis (central consensus scoring in database); NSAID, non-steroidal anti-inflammatory drug; SSS, Sacroiliitis Sum Score; TNFi, tumour necrosis factor inhibitor.