Table 3.
Characteristics of patients with axSpA with early disease and established disease at start of first TNF inhibitor in the main adjusted retention analysis (model 1; patients without missing covariate data)
| Parameter | All patients diagnosed as having axSpA (main analysis; N=843) |
Patients fulfilling the ASAS classification criteria (sensitivity analysis; N=816) |
||||||||
| N | Early disease (≤2 years) N=178 |
N | Established disease (>2 years) N=665 |
P value | N | Early disease (≤2 years) N=114 |
N | Established disease (>2 years) N=509 |
P value | |
| Male sex, N (%) | 178 | 95 (53.4) | 665 | 333 (50.1) | 0.49 | 114 | 64 (56.1) | 509 | 275 (54.0) | 0.76 |
| Age, years | 178 | 37.6 (13.0) | 665 | 43.7 (12.3) | <0.001 | 114 | 32.4 (9.4) | 509 | 41.5 (11.5) | <0.001 |
| Symptom duration, years, median (IQR) | 176 | 1.4 (0.8–2.6) | 661 | 10.9 (5.9–19.8) | <0.001 | 113 | 1.5 (0.8–2.6) | 506 | 11.2 (6.1–20.7) | <0.001 |
| Axial symptom duration, years, median (IQR) | 178 | 0.8 (0.5–1.2) | 665 | 10.2 (5.2–19.2) | <0.001 | 114 | 0.8 (0.5–1.2) | 509 | 10.7 (5.6–19.9) | <0.001 |
| Time since diagnosis, years, median (IQR) | 177 | 0.4 (0.2–1.0) | 658 | 2.5 (0.5–8.9) | <0.001 | 114 | 0.3 (0.2–0.9) | 503 | 2.6 (0.5–9.4) | <0.001 |
| HLA-B27 positive, N (%) | 178 | 104 (58.4) | 665 | 437 (65.7) | 0.09 | 114 | 82 (71.9) | 509 | 384 (75.4) | 0.51 |
| Family history axSpA, N (%) | 168 | 33 (19.6) | 623 | 148 (23.8) | 0.31 | 110 | 24 (21.8) | 480 | 130 (27.1) | 0.31 |
| Body mass index | 133 | 24.9 (4.4) | 630 | 25.7 (4.5) | 0.02 | 109 | 24.3 (4.4) | 488 | 25.5 (4.4) | 0.003 |
| Current smoking, N (%) | 177 | 63 (35.6) | 655 | 227 (34.7) | 0.79 | 113 | 43 (38.1) | 502 | 184 (36.7) | 0.36 |
| Education | 178 | 665 | 0.36 | 114 | 509 | 0.88 | ||||
|
26 (14.6) | 112 (16.8 | 17 (14.9) | 80 (15.7) | ||||||
|
110 (61.8) | 371 (55.8) | 67 (58.8) | 286 (56.2) | ||||||
|
42 (23.6) | 182 (27.4) | 30 (26.3) | 143 (28.1) | ||||||
| Back pain due to axSpA* ≥3 months, N (%) | 178 | 178 (100.0) | 665 | 665 (100.0) | N/A | 114 | 114 (100.0) | 509 | 509 (100.0) | N/A |
| Inflammatory back pain, N (%) | 164 | 122 (74.4) | 630 | 535 (84.9) | 0.002 | 114 | 87 (76.3) | 507 | 449 (88.6) | 0.001 |
| Sacroiliitis ever* | ||||||||||
|
159 | 109 (68.6) | 593 | 417 (70.3) | 0.74 | 109 | 83 (76.1) | 482 | 351 (72.8) | 0.56 |
|
161 | 31 (19.3) | 597 | 163 (27.3) | 0.048 | 111 | 25 (22.5) | 485 | 145 (29.9) | 0.15 |
|
159 | 91 (57.2) | 593 | 266 (44.9) | 0.01 | 109 | 63 (67.0) | 482 | 244 (50.6) | 0.003 |
| Spine involvement ever* | ||||||||||
|
159 | 109 (68.6) | 596 | 432 (72.5) | 0.38 | 109 | 76 (69.7) | 485 | 353 (72.8) | 0.60 |
|
159 | 10 (6.3) | 596 | 86 (14.4) | 0.01 | 109 | 6 (5.5) | 485 | 75 (15.5) | 0.01 |
|
159 | 47 (29.6) | 596 | 163 (27.3) | 0.65 | 109 | 28 (25.7) | 485 | 136 (28.0) | 0.71 |
| Ever peripheral arthritis, N (%) | 166 | 75 (45.2) | 627 | 280 (44.7) | 0.97 | 114 | 52 (45.6) | 506 | 208 (41.1) | 0.48 |
| Ever enthesitis, N (%) | 165 | 110 (66.7) | 619 | 446 (72.1) | 0.21 | 113 | 76 (67.3) | 500 | 357 (71.4) | 0.45 |
| Ever uveitis, N (%) | 129 | 16 (12.4) | 480 | 74 (15.4) | 0.47 | 86 | 12 (14.0) | 388 | 66 (17.0) | 0.60 |
| Ever psoriasis, N (%) | 130 | 19 (14.6) | 471 | 56 (11.9) | 0.50 | 87 | 11 (12.6) | 379 | 43 (11.3) | 0.88 |
| Ever inflammatory bowel disease, N (%) | 123 | 12 (9.8) | 466 | 42 (9.0) | 0.94 | 84 | 9 (10.7) | 375 | 31 (8.3) | 0.61 |
| Physician global disease activity | 152 | 5.0 (1.9) | 556 | 4.6 (1.8) | 0.01 | 105 | 5.1 (2.0) | 446 | 4.6 (1.8) | 0.04 |
| Patient global disease activity | 142 | 6.0 (2.3) | 535 | 6.1 (2.4) | 0.35 | 97 | 5.9 (2.3) | 427 | 6.1 (2.4) | 0.31 |
| BASDAI | 138 | 5.5 (2.0) | 529 | 5.4 (2.0) | 0.87 | 95 | 5.5 (2.0) | 420 | 5.3 (2.0) | 0.41 |
| ASDAS | 130 | 3.3 (0.9) | 484 | 3.3 (0.9) | 0.70 | 90 | 3.3 (0.9) | 392 | 3.2 (0.9) | 0.39 |
| ASDAS ≥2.1 | 130 | 119 (91.5) | 484 | 440 (90.9) | 0.96 | 90 | 82 (91.1) | 392 | 355 (90.6) | 1.00 |
| Elevated CRP, N (%) | 145 | 69 (47.6) | 541 | 236 (43.6) | 0.45 | 101 | 51 (50.5) | 437 | 202 (46.2) | 0.51 |
| CRP (mg/L), median (IQR) | 146 | 5.9 (2.9–16.0) | 541 | 6.0 (2.0–13.0) | 0.78 | 101 | 6.0 (2.0–18.0) | 437 | 6.5 (2.0–14.0) | 0.69 |
| BASFI | 138 | 3.7 (2.4) | 521 | 3.7 (2.4) | 0.97 | 95 | 3.7 (2.5) | 416 | 3.6 (2.4) | 0.73 |
| BASMI | 136 | 1.3 (1.3) | 509 | 2.1 (1.9) | <0.001 | 96 | 1.2 (1.3) | 410 | 2.0 (1.9) | <0.001 |
| EQ-5D | 138 | 56.7 (20.3) | 511 | 59.1 (20.5) | 0.10 | 95 | 57.2 (20.6) | 408 | 60.4 (20.5) | 0.09 |
| SF-12, physical component summary score | 131 | 35.6 (9.4) | 477 | 36.2 (9.2) | 0.49 | 91 | 36.3 (9.6) | 386 | 37.0 (9.3) | 0.47 |
| SF-12, mental component summary score | 131 | 40.7 (9.8) | 477 | 42.3 (11.2) | 0.15 | 91 | 39.8 (9.7) | 386 | 42.5 (11.1) | 0.03 |
| Non-steroidal antirheumatic drugs, N (%) | 114 | 110 (96.5) | 396 | 377 (95.2) | 0.74 | 75 | 74 (98.7) | 321 | 306 (95.3) | 0.32 |
| Conventional synthetic DMARDs, N (%) | 178 | 26 (14.6) | 664 | 83 (12.5) | 0.54 | 114 | 16 (14.0) | 509 | 53 (10.4) | 0.35 |
Except where indicated otherwise, values represent the mean and SD.
*Information provided by the local rheumatologist with unknown total number of patients with imaging performed.
ASAS, Assessment of SpondyloArthritis international Society; ASDAS, Ankylosing Spondylitis Disease Activity Score; axSpA, axial spondyloarthritis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Metrology Index; CRP, C reactive protein; DMARDs, disease-modifying antirheumatic drugs; EQ-5D, European Quality of Life 5-domains Questionnaire; HLA-B27, human leucocyte antigen-B27; N/A, not applicable; SF-12, Short Form Questionnaire with 12 questions; TNF, tumour necrosis factor.