Baseline demographic, clinical and radiographic characteristics of all patients and the sensitivity analysis group*
| Assessment | Patients included in this study N=184 mean (SD) or n (%) | Sensitivity analysis group* N=85 mean (SD) or n (%) |
|---|---|---|
| Age (years) | 43 (12) | 40 (10) |
| Male gender (%) | 129 (70) | 65 (76) |
| HLA-B27 positive (%) | 149 (83) | 70 (82) |
| Symptoms duration (years) | 20 (12) | 16 (9) |
| Disease duration (years) | 11 (9) | 9 (8) |
| ASDAS-CRP | 2.6 (1.0) | 2.7 (1.1) |
| BASDAI (0–10) | 3.4 (2.0) | 3.3 (2.2) |
| CRP (mg/L) | 17.4 (23.3) | 19.0 (24.9) |
| Elevated CRP (%)† | 85 (48) | 44 (54) |
| mSASSS (0–72) | 10.8 (15.2) | 7.8 (11.3) |
| mSASSS >0 (%) | 140 (81) | 62 (81) |
| NSAIDs (%) | 125 (68) | 60 (71) |
| Tumour necrosis factor α inhibitors (%) | 0 (0) | 0 (0) |
| University education (%) | 14 (8) | 7 (8) |
| Monthly personal income ≥€1588 (%) | 56 (35) | 34 (40) |
| Monthly family income ≥€3176 (%) | 21 (19) | 13 (23) |
| Smoker (%) | 49 (39) | 35 (41) |
| Blue-collar worker (%) | 65 (48) | 40 (47) |
*Sensitivity analysis group: patients included in the study and with the following variables available: occupational activity, smoking status, education and personal income (availability of family income was not demanded because of the higher number of missing values in this variable).
†The cut-off was 10 mg/L for the Dutch patients and 5 mg/L for the Belgian and French patients.
ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score (C reactive protein); BASDAI, Bath Ankylosing Spondylitis Disease Activity Score; CRP, C reactive protein; mSASSS, modified Stoke Ankylosing Spondylitis Spine Score; NSAIDs, non-steroidal anti-inflammatory drugs.