Baseline characteristics of the patients with regard to their status during the 10-year follow-up period
| Baseline characteristics | Completers | Lost to follow-up | Documented change in the baseline diagnosis | Whole population |
| n=360 | n=300 | n=45 | n=708 | |
| Age (years)* | 34±9 | 32±8 | 36±8 | 34±9 |
| Female | 192 (53%) | 163 (54%) | 24 (53%) | 381 (54%) |
| Ethnicity (white caucasian) | 328 (91%) | 266 (89%) | 44 (98%) | 641 (91%) |
| Educational level: university | 231 (64%) | 159 (54%) | 28 (62%) | 418 (59%) |
| Time from first symptoms to baseline (years) | 1.5±0.9 | 1.6±0.9 | 1.5±0.9 | 1.5±0.9 |
| HLA B27: positive | 231 (64%) | 160 (54%) | 18 (40%) | 410 (58%) |
| Extraspinal manifestations (past or present) | ||||
| Enthesitis | 177 (49%) | 147 (49%) | 22 (49%) | 348 (49%) |
| Synovitis | 85 (24%) | 62 (21%) | 2 (4%) | 151 (21%) |
| Dactylitis | 50 (14 %) | 39 (13%) | 1 (2 %) | 92 (13%) |
| Extramusculoskeletal manifestations (past or present) | ||||
| Psoriasis | 67 (19%) | 48 (16%) | 3 (7%) | 119 (17%) |
| Uveitis | 35 (10%) | 23 (8%) | 1 (2%) | 60 (8%) |
| IBD | 17 (5 %) | 11 (4%) | 0 (0 %) | 28 (4%) |
| Disease activity | ||||
| BASDAI (0–100) | 43±21 | 46±20 | 50±16 | 45±20 |
| ASDAS | 2.6±1.0 | 2.7±1.0 | 2.6±0.6 | 2.7±0.9 |
| CRP (mg/L) | 8.6±14.0 | 7.7±13.0 | 2.3±2.5 | 7.9±13.5 |
| MRI-SIJ inflammation† | 143 (41%) | 86 (30%) | 2 (5%) | 231 (34%) |
| X-rays SIJ structural damage‡ | 112 (32%) | 72 (25%) | 2 (4%) | 187 (27%) |
| Quality of life/impact | ||||
| BASFI | 29.4±23.1 | 31.4±22.6 | 32.1±21.4 | 30.5±22.8 |
| SF-36 Physical score | 39.9±9.6 | 38.7±9.2 | 37.2±9.9 | 39.2±9.5 |
| SF-36 Mental score | 41.4±11.1 | 38.9±11.2 | 39.1±12.3 | 40.2±11.3 |
| PASS | 156 (44%) | 117 (39%) | 15 (33%) | 290 (41%) |
*Values given are mean±SD for continuous variables and numbers (percentage) for binary variables.
†MRI-SIJ-inflammation=presence of inflammation at the acroiliac level on MRI based on the opinion of the local reader (either radiologist or rheumatologist).
‡X-rays-SIJ structural damage=presence of structural damage suggestive of axSpA on pelvic X-rays based on the local reader (either radiologist or rheumatology).
ASDAS, Axial Spondyloarthritis Disease activity score; BASDAI, Bath Akylosing Spondylitis Disease Activity Index ; BASFI, Bath Akylosing Spondylitis Functional Index ; CRP, C-reactive protein; HLAB27, Human Leucocyte Antigen 27; IBD, inflammatory bowel disease; PASS, patient acceptable symptom state; SF-36, Short Form questionnaire 36; SIJ, Sacroiliac joints.