Table 1.
Demographic data of study participants.
| Variables | Healthy | RA-Risk | RA |
|---|---|---|---|
| Sex (female) (n) (%) | 9 (64) | 20 (87) | 17 (70) |
| Age (years) (median (IQR)) | 29 (26–37) † | 49 (35–57) | 56 (44–61) |
| IgM-RF positive (n) (%) | 0 (0) | 10 (43) | 20 (3–107) |
| IgM-RF level (kU/mL) (median (IQR)) | — | 20 (3–107) | 131 (31–309) |
| ACPA positive (n) (%) | 0 (0) | 13 (57) | 18 (75) |
| ACPA level (kAU/L) (median (IQR)) | — | 43 (4–177) | 115 (21–924) |
| IgM-RF and ACPA both positive (n) (%) | 0 (0) | 0 (0) | 14 (58) |
| DAS28 (median (IQR)) | — | — | 5 (1–10) a,b |
| ESR (mm/h) (median (IQR)) | — | 7 (2–10) | 11 (5–27) c |
| CRP (mg/L) (median (IQR)) | 0.5 (0.3–1.2) a | 1.6 (0.9–3.2) | 4.6 (1.4–13) d |
| 68TJC (median (IQR)) | 0 (0) | 1.5 (0–4.5) | 9 (4–20) e |
| 68SJC (median (IQR)) | 0 (0) | 0 (0) | 5 (1–10) d |
| Treatment (n) (%) | 9 (39) | ||
| Corticoids | 6 (26) | ||
| NSAID | 4 (17) f | ||
| DMARD | 5 (22) | ||
| Failed TNF inhibitor therapy | 5 (22) |
IgM-RF, IgM rheumatoid factor; ACPA, anti-citrullinated protein antibodies; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; TJC, tender joint count; NSAID, non-steroidal anti-inflammatory drug; DMARD, disease-modifying antirheumatic drugs. a levels missing from one individual, b levels missing from two individuals, c levels missing from six individuals, d levels missing from seven individuals, e levels missing from five individuals, f treatment unknown for five individuals. † Healthy individuals are significantly younger than RA-risk individuals and RA patients (p < 0.0050, tested by Kruskal–Wallis followed by a post Dunn’s test).