Table 1 Population characteristics and median serum calprotectin levels in each group. All results are mean (with standard deviation), except those with an asterisk* which are median [with interquartile range] and those marked with a “^§” which are number of patients (%). Abbreviations: BMI body mass index, CRP C-reactive protein, ESR erythrocyte sedimentation rate, GCS glucocorticoids, cDMARDS conventional disease-modifying anti-rheumatic drugs, bDMARDS biological disease-modifying anti-rheumatic drugs, TNFi TNF inhibitors

n

969

451

237

72

Gender = male^§

250 (25.8)

268 (59.4)

136 (57.4)

13 (18.1)

< 0.01

Age, year

57.6 (13.2)

44.0 (12.3)

51.5 (12.2)

56.5 (8.3)

< 0.01

Disease duration, year

10.9 (10.1)

9.9 (9.8)

7.9 (8.4)

–

< 0.01

BMI kg/m²

26.2 (5.4)

26.0 (4.9)

27.5 (5.4)

24.1 (3.4)

< 0.01

Smoker^§

435/758 (57.4)

146/264 (55.3)

101/168 (60.1)

34/72 (47.2)

0.37

Calprotectin μg/ml*

2.6 [1.7, 4.3]

2.4 [1.6, 3.9]

2.2 [1.4, 3.4]

1.2 [0.8, 2.0]

< 0.01

CRP mg/l*

3.0 [1.0, 7.9]

3.0 [1.0, 8.0]

3.0 [1.0, 7.9]

–

0.39

ESR mm/h*

12.0 [6.0, 22.0]

8.0 [4.0, 17.0]

8.0 [3.0, 14.0]

–

0.62

Swollen joint count*

1.0 [0.0, 3.0]

0.0 [0.0, 0.0]

0.0 [0.0, 2.0]

–

< 0.01

Disease activity score¹

2.8 [2.0, 3.9]

2.3 [1.5, 3.2]

12 [5.1, 24.0]

–

Patients on GCS^§

277 (28.6)

3 (0.7)

19 (8.0)

–

< 0.01

Patients on cDMARDS^§

645 (66.6)

75 (16.6)

142 (59.9)

–

< 0.01

Patients on bDMARDS^§

557 (57.5)

184 (40.8)

108 (45.6)

–

< 0.01

TNFi^§

205 (21.2)

180 (39.9)

100 (42.2)

< 0.01

Tocilizumab^§

92 (9.5)

3 (0.7)

3 (1.3)

< 0.01

Rituximab^§

172 (17.8)

0 (0.0)

1 (0.4)

< 0.01