Table 1 Comparison of demographic characteristics of IgG4-RD with and without hypocomplementemia at baseline

 Gender (male), n (%)

47 (72.3%)

144 (59.0%)

0.05

 Age of diagnosis, mean ± SD

55.85 ± 10.89

53.05 ± 13.00

0.113

 Duration of disease (medium months, IQR)

12 (4, 36)

12 (6, 48)

0.131

 Allergy history (n, %)

40 (61.5%)

125 (51.2%)

0.139

 Number of organs involved (mean ± SD)

4.88 ± 1.79

2.89 ± 1.36

< 0.001***

 IgG4-RD RI, mean ± SD

15.74 ± 5.78

9.64 ± 4.33

< 0.001***

 Lymph node

43 (66.2%)

88 (36.1%)

< 0.001***

 Lacrimal gland

43 (66.2%)

111 (45.5%)

0.003**

 Submandibular gland

41 (63.1%)

101 (41.4%)

0.001**

 Pancreas

33 (50.8%)

66 (27.1%)

< 0.001***

 Lung

33 (50.8%)

44 (18.0%)

< 0.001***

 Paranasal sinus

27 (41.5%)

68 (27.9%)

0.029*

 Parotid gland

22 (33.8%)

28 (11.5%)

< 0.001***

 Bile duct

20 (30.8%)

35 (14.3%)

0.002**

 Kidney

12 (18.5%)

26 (10.7%)

0.082

 Prostate gland

10 (15.4%)

10 (4.1%)

0.0218*

 Retroperitoneum

8 (12.3%)

46 (18.9%)

0.229

 Aorta/artery

5 (7.7%)

28 (11.5%)

0.442

 Pituitary

3 (4.6%)

7 (2.9%)

0.443

 Gastrointestinal tract

0 (0.0%)

4 (1.6%)

 Mediastinum

3 (4.6%)

6 (2.5%)

0.349

 Thyroid (Riedel’s)

3 (4.6%)

10 (4.1%)

0.835

 C3(normal 0.73–1.46 g/L)

0.54 ± 0.17

0.99 ± 0.33

< 0.001***

 C4(normal 0.10–0.40 g/L)

0.061 ± 0.047

0.19 (0.14,0.25)

< 0.001***

 WBC(10⁹/L)

6.67 ± 1.84

6.54 (5.58, 7.75)

0.894

 HGB(g/L)

132.35 ± 18.38

134.37 ± 22.07

0.508

 PLT(10⁹/L)

215.80 ± 59.00

240.30 ± 75.80

0.017*

 EOS(10⁹/L)

0.39 (0.14,0.69)

0.19 (0.10,0.33)

0.001**

 ESR (mm/H)

46.34 ± 32.40

16 (7, 37)

< 0.001***

 hsCRP (mg/L) (normal<  8mg/L)

2.5 1(0.82, 8.64)

1.86 (0.64, 5.68)

0.117

 IgG (normal 7.0–17.0 g/L)

30.92 ± 15.31

18.05 ± 8.79

< 0.001***

 IgA (normal 0.7–4.0 g/L)

1.59 ± 0.78

2.36 ± 1.32

< 0.001***

 IgM (normal 0.4–2.3 g/L)

0.87 ± 0.63

0.81 (0.54, 1.23)

0.132

 IgE (KU/L)(normal<60KU/L)

471.0 (246.75, 880.00)

222.00 (63.70, 609.00)

< 0.001***

 IgG1(normal 490–1140 mg/dL)

1295.11 ± 539.48

907.73 ± 439.79

< 0.001***

 IgG2(normal 150–640 mg/dL)

666.83 ± 542.76

612.56 ± 256.77

0.259

 IgG3(normal 20–110 mg/dL)

100.56 ± 80.81

50.54 ± 41.23

< 0.001***

 IgG4(normal 80–135 mg/dL)

2614.13 ± 1915.39

547.50 (274.23,1215.50)

< 0.001***

 IgG4/IgG

0.80 ± 0.44

0.44 ± 0.34

< 0.001***

 RF positive (n, %)

20 (n = 57, 35.1%)

44 (n = 166, 26.5%)

0.217