Table 1 Baseline characteristics of patients with “seronegative” and “seropositive” early arthritis (n = 748)

Female, n (%)

274 (77.4%)

305 (77.4%)

0.997

Age (years), mean (SD)

48.9 (13.2)

47.7 (11.9)

0.058

Caucasian, n (%)

330 (93.2%)

359 (91.1%)

0.287

Current tobacco exposure, n (%)

173 (48.9%)

187 (47.5%)

0.700

Current alcohol consumption, n (%)

61 (17.2%)

71 (18%)

0.778

Symptom duration at first visit (months), mean (SD)

3.4 (1.7)

3.4 (1.8)

0.693

Morning stiffness (min), mean (SD)

75.6 (144.6)

110.1 (214.8)

0.008

Pain at rest (VAS, 0–100), mean (SD)

37.2/100 (27.6)

38/100 (27.5)

0.684

TJC, mean (SD)

8.8 (7.2)

8.3 (6.9)

0.521

SJC, mean (SD)

7.1 (5.5)

7.6 (5.4)

0.077

Extra-articular manifestations ♯

188/346 (54.3%)

191/383 (52.5%)

0.228

Anti-CCP positive, n (%)

0

325 (82.5%)

–

Anti-CCP, units/ml mean (SD)

0.2 (1.3)

292.3 (201.7)

< 0.001

IgM-RF positive, n (%)

0

358 (90.9%)

–

IgM-RF, IU/ml, mean (SD)

4.6 (1.5)

238.5 (770.8)

< 0.001

ANA positive, n (%)

45 (12.8%)

111 (28.5%)

< 0.001

ESR, mm/h, mean (SD)

25.8 (23.3)

32.9 (24.8)

< 0.001

CRP level, mg/L mean (SD)

18.3 (33.1)

21.9 (30.6)

< 0.001

DAS28, mean (SD)

5.0 (1.3)

5.3 (1.3)

0.002

HAQ-DI, mean (SD)

0.9 (0.7)

1 (0.7)

0.030

mTSS, mean (SD)

4.3 (6)

5.7 (8.2)

0.026

HLA-DRΒ1*01 or 04 gene, n (%)

112 (31.6%)

241 (61.2%)

< 0.001

HLA-DRΒ1*03 gene, n (%)

77 (21.8%)

60 (15.2%)

0.021

2010 ACR/EULAR criteria (≥ 6/10 points), n (%)

224/340 (65.9%)

386/394 (98.0%)

< 0.001

 Based on score ≥ 6

206/353 (58.4%)

384/394 (97.5%)

< 0.001

 Typical RA erosion

60/318 (18.9%)

113/362 (31.2%)

< 0.001