Table 1.
Characteristics of patients with axial spondyloarthritis at inclusion in the cohort
| Parameter | nr-axSpA N=485 (23.3%) |
r22axSpA N=443 (21.3%) |
r3+axSpA N=1152 (55.4%) |
All N=2080 |
Overall P value |
| Male sex, N (%) | 225 (46.4) | 253 (57.1)† | 829 (72.0)*† | 1307 (62.8) | <0.001 |
| Age (years) | 37.0 (10.9) | 39.3 (11.0)† | 40.8 (11.3)*† | 39.6 (11.2) | <0.001 |
| Age at first symptoms (years) | 28.2 (8.6) | 27.2 (8.0) | 25.4 (8.4)*† | 26.4 (8.4) | <0.001 |
| Disease duration (years) | 8.8 (9.4) | 12.1 (10.7)† | 15.5 (11.1)*† | 13.2 (11.0) | <0.001 |
| Body mass index | 24.9 (4.2) | 25.8 (4.6)† | 25.5 (4.5)† | 25.4 (4.5) | 0.006 |
| Current smoker, N (%) | 131 (31.3) | 120 (31.7) | 417 (42.1)*† | 668 (37.4) | <0.001 |
| Family history of SpA, N (%) | 255 (62.2) | 245 (64.6) | 602 (64.2) | 1102 (63.8) | 0.72 |
| HLA-B27 positivity, N (%) | 334 (74.5) | 286 (71.3) | 853 (82.5)*† | 1472 (78.2) | 0.002 |
| BASFI | 3.0 (2.4) | 3.2 (2.5) | 3.6 (2.6)† | 3.4 (2.6) | <0.001 |
| BASMI | 1.2 (1.2) | 1.6 (1.6)† | 2.6 (2.2)*† | 2.1 (2.0) | <0.001 |
| BASDAI | 5.0 (2.2) | 4.7 (2.3) | 4.6 (2.3) | 4.7 (2.3) | 0.07 |
| ASDAS | 2.9 (0.9) | 2.9 (1.0) | 3.1 (1.1)*† | 3.0 (1.1) | 0.001 |
| Elevated CRP, N (%) | 122 (27.1) | 130 (32.1) | 552 (51.3)*† | 804 (41.6) | <0.001 |
| Elevated CRP >15 mg/L, N (%) | 52 (11.5) | 61 (15.0) | 312 (28.8)*† | 425 (21.9) | <0.001 |
| Elevated CRP >30 mg/L, N (%) | 22 (4.9) | 22 (5.4) | 137 (12.7)*† | 181 (9.3) | <0.001 |
| Elevated ESR >20 mm/hour, N (%) | 76 (17.0) | 92 (23.3) | 381 (35.6)*† | 549 (28.7) | <0.001 |
| Elevated ESR >30 mm/hour, N (%) | 35 (7.8) | 46 (11.7) | 236 (22.1)*† | 317 (16.6) | <0.001 |
| CRP (mg/L), median (IQR) | 3.5 (1; 8) | 5 (2; 9) | 8 (3; 16)*† | 6 (2; 13) | <0.001 |
| Current hip arthritis, N (%) | 36 (7.6) | 29 (6.8) | 204 (18.5)*† | 269 (13.4) | <0.001 |
| Current peripheral arthritis, N (%) | 182 (37.8) | 108 (24.7)† | 353 (31.2)*† | 643 (31.4) | <0.001 |
| Current enthesitis, N (%) | 343 (71.9) | 293 (68.0) | 665 (59.4)*† | 1301 (64.2) | <0.001 |
| Uveitis ever, N (%) | 64 (15.0) | 80 (20.0) | 280 (27.2)*† | 424 (22.8) | <0.001 |
| Psoriasis ever, N (%) | 32 (8.7) | 35 (10.3) | 102 (12.4) | 169 (11.1) | 0.17 |
| Inflammatory bowel disease ever, N (%) | 27 (6.4) | 42 (10.8) | 113 (11.3)† | 182 (10.0) | 0.01 |
| Current tumour necrosis factor inhibitor use, N (%) | 77 (15.9) | 118 (26.6)† | 285 (24.8)† | 480 (23.1) | <0.001 |
| csDMARD use ever, N (%) | 151 (31.1) | 137 (30.9) | 370 (32.2) | 658 (31.7) | 0.84 |
Except where indicated otherwise, values are the mean with corresponding SD in brackets. Significance levels of two-group comparisons are Bonferroni-corrected.
*P<0.15 compared with 22axSpA.
†P<0.15 compared with nr-axSpA.
ASDAS, Ankylosing Spondylitis Disease Activity Score; 22axSpA, axial spondyloarthritis with bilateral grade sacroiliitis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Mobility Index; CRP, C reactive protein; csDMARD, conventional synthetic disease-modifying antirheumatic drug; ESR, erythrocyte sedimentation rate; HLA-B27, human leucocyte antigen B27; nr-axSpA, non-radiographic axial spondyloarthritis; r3+axSpA, unilateral/bilateral grade 3–4 radiographic sacroiliitis; r22axSpA, bilateral grade 2 sacroiliitis.;