| Characteristic | Value |
| Age (years), mean (SD) {range} | 44 (13) {19–78} |
| Sex (% male) | 71 |
| Disease duration (years), mean (SD) {range} | 11 (9) {0–42} |
| Duration of complaints (years), mean (SD) {range} | 20 (12) {0–54} |
| BASDAI, mean (SD) {range}, % ⩾4 | 3.4 (2.1) {0–9.7}, 38 |
| BASFI, mean (SD) {range}, % ⩾4 | 3.4 (2.6) {0–10}, 41 |
| DFI, mean (SD) {range} | 21 (15) {0–72} |
| ESR (mm), median (25%; 75%) {range} % ⩾28 mm | 9 (4; 17) {0–118}, 11 |
| CRP (mg/l), median (25%; 75%) {range}, % ⩾10 mg/l | 7 (6; 17) {0–139}, 41 |
| HLA-B27 positive (%) | 84 |
| Hip involvement (%) | 24 |
| mSASSS (units), median (25%; 75%) {range}, % patients >0 | 5 (0; 18) {0–72}, 69 |
| VUs with bridging (n), median (25%; 75%) {range}, % patients >0 | 0 (0; 2) {0–12}, 41 |
BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; CRP, C-reactive protein; DFI, Dougados Functional Index; ESR, erythrocyte sedimentation rate; mSASSS, modified Stoke Ankylosing Spondylitis Spine Score; VU, vertebral unit.