Table 1 Extra and no-extra groups clinical data

Age [years, mean ± SD]

60.4 ± 10.1

55.4 ± 12.1

 < 0.001

Sex (female) [n, %]

233 (89.3%)

764 (89.5%)

0.931

RF positive [n, %]

204 (80.6%)

N = 253

659 (78.1%)

N = 844

0.385

 RF low titer < 3x [n,%]

45 (22.1%)

202 (30.7%)

0.018

 RF high titer ≥ 3x [n,%]

159 (77.9%)

457 (69.3%)

ACPA positivity

68 (71.6%)

N = 95

300 (78.3%)

N = 383

0.162

Disease duration [years, mean ± SD]

17.4 ± 10.5

13.7 ± 9.1

 < 0.001

Smoker, ever [n, %]

110 (42.1%)

330 (38.6%)

0.311

Smoker, current [n, %]

25 (9.6%)

96 (11.2%)

0.450

CDAI [mean ± SD]

18.2 ± 16.1

11.5 ± 10.7

 < 0.001

DAS28-ESR [mean ± SD]

4.3 ± 1.7

3.4 ± 1.4

 < 0.001

DAS28-CRP

[mean ± SD]

3.7 ± 1.6

3.2 ± 1.3

 < 0.001

HAQ-DI [mean ± SD]

1.16 ± 0.83

0.88 ± 0.74

 < 0.001

ESR [mm, mean ± SD]

35.6 ± 26.5

25.9 ± 23.3

 < 0.001

CRP [mg/L, mean ± SD]

2.9 ± 6.9

1.6 ± 3.0

 < 0.001

Erosive disease [n,%]

181 (71.3%)

N = 254

420 (49.9%)

N = 841

 < 0.001