Baseline characteristics according to the availability of complete 5-year radiographic data of the sacroiliac joints
| Characteristics | Status at year 5 | ||
| Completers* | Non-completers | All patients | |
| Number of patients | 417 | 291 | 708 |
| Age (mean, SD) | 34.1 (8.6) | 33.2 (8.6) | 33.7 (8.6) |
| Symptom duration (years), (mean, SD) | 1.5 (0.9) (n=416) | 1.5 (0.8) (n=291) | 1.5 (0.9) (n=707) |
| Male gender (%) | 198 (47.5) | 129 (44.3) | 327 (46.2) |
| HLA-B27 positivity (%) | 267 (64.0) (n=417) | 143 (49.3) (n=290) | 410 (58.0) (n=707) |
| X-SIJ structural damage† (mNY) (%) | 62 (14.9) (n=416) | 29 (10.8) (n=268) | 92 (13.5) (n=684) |
| MRI-SIJ inflammation†‡ (%) | 113 (28.1) (n=402) | 67 (24.2) (n=277) | 180 (26.5) (n=679) |
| Abnormal CRP§ (%) | 126 (31.5) (n=400) | 78 (27.4) (n=285) | 204 (29.8) (n=685) |
| BASDAI (0–10, mean, SD) | 4.34 (1.99) (n=416) | 4.65 (2.01) (n=288) | 4.47 (2.00) (n=704) |
| ASDAS (mean, SD) | 2.6 (1.0) (n=395) | 2.6 (0.9) (n=281) | 2.6 (1.0) (n=676) |
| BASFI (0–10, mean, SD) | 2.92 (2.24) (n=413) | 3.23 (2.32) (n=288) | 3.04 (2.28) (n=701) |
*Patients with both baseline and 5-year X-SIJ available.
†According to the ‘2 out of 3’ definition: agreement of at least two out of the three readers—if two readers disagree and the third reading is missing, the combined score is set as missing (one case for X-SIJ).
‡Presence of bone marrow oedema according to the ASAS criteria at MRI-SIJ.
‡≥6 mg/L.
ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; CRP, C reactive protein; mNY, modified New York criteria; MRI-SIJ, MRI of the sacroiliac joints; X-SIJ, radiograph of the sacroiliac joints.