Baseline characteristics (n=219)
| Variable | ACPA-positive individuals* (n=109) | RF-positive individuals* (n=53) | Seronegative individuals with CSA (n=57) | FDRs of patients with RA† (n=18) |
| Age‡ | 49 (12.9) | 54 (13.2) | 45 (12.6) | 57 (9.5) |
| Females (%) | 72 | 64 | 72 | 89 |
| Symptom duration (months)§ | 23 (10–52) | 30 (12–60) | 11 (4–39) | 22 (7–51) |
| Tender joint count (44 joints) | 0 (0–2) | 0 (0–2) | 2 (0–7) | 1 (0–3) |
| VAS pain (mm)§ | 18 (2–56) | 27 (3–47) | 56 (34–71) | ND |
| VAS patient global assessment (mm)§ | 28 (3–56) | 22 (0–49) | 48 (25–69) | ND |
| VAS fatigue (mm)§ | 50 (9–80) | 33 (6–59) | 65 (40–82) | ND |
| Current smoking (%) | 24 | 15 | 25 | 17 |
| FDR with RA (%)§ | 29 | 21 | 28 | 100 |
*ACPA-positive individuals: with or without RF positivity, RF-positive individuals: only RF-positive.
†FDRs of patients from Switzerland with RA were used as comparison cohort.
‡Mean (SD), all other continuous variables mentioned as median (25th–75th percentile).
§Missing values; 2% for VAS global and family history, 3% for VAS pain, 4% for VAS fatigue, 6% for symptom duration, one individual for RF (marked as ACPA positive only now).
Netherlands: ACPA+ n=71; RF+ n=40; seronegative n=14.
UK: ACPA+ n=21; RF+ n=8; seronegative n=40.
Sweden: ACPA+ n=15; RF+ n=0; seronegative n=0.
Austria: ACPA+ n=2; RF+ n=5; seronegative n=3.
Switzerland: ACPA+ n=6; RF+ n=1; seronegative n=11.
ACPA, anticitrullinated protein antibodies; CSA, clinically suspect arthralgia; FDR, first degree relative; ND, not done; RA, rheumatoid arthritis; RF, rheumatoid factor; VAS: Visual Analogue Scale.