Abstract:

Objective To investigate the optimal cut-off value and performance of serum immunoglobulin（Ig）G4 and IgG4/IgG ratio in the diagnosis of typeⅠ autoimmune pancreatitis（AIP）. Methods Serum IgG subclass（IgG1,IgG2,IgG3 and IgG4） levels in 47 patients with type Ⅰ AIP,109 patients with pancreatic cancer or cholangiocarcinoma（disease control group） and 99 healthy subjects（healthy control group） were determined by immunonephelometry. Receiver operating characteristic（ROC） curve was used to identify the optimal cut-off values and the area under curve（AUC） of serum IgG4 and IgG4/IgG ratio for the diagnosis of typeⅠ AIP. Results The levels of serum IgG2,IgG4,IgG and IgG4/IgG ratio in typeⅠ AIP group were higher than those in healthy control group（P<0.001）. The levels of serum IgG1,IgG3,IgG4 and IgG4/IgG ratio in disease control group were lower than those in healthy control group（P<0.05）. The proportion of elevated IgG4 level in type Ⅰ AIP group（95.7%） was higher than those in disease control group（3.7%） and healthy control group（2.0%）（P<0.001）,and there was no statistical significance between disease and healthy control groups（P>0.05）. The AUC of serum IgG4 for the diagnosis of typeⅠ AIP was 0.992,and the optimal cut-off value was 1 740 mg/L. The sensitivity,specificity and accuracy were 97.9%,96.2% and 96.5%. The AUC of IgG4/IgG ratio for the diagnosis of typeⅠ AIP was 0.988,the optimal cut-off value was 0.103,and the sensitivity,specificity and accuracy were 97.9%,93.8% and 94.5%. There was no statistical significance for the AUC of serum IgG4 and IgG4/IgG ratio in the diagnosis of type Ⅰ AIP（P>0.05）. Conclusions Serum IgG4 level and IgG4/IgG ratio play roles in the diagnosis of typeⅠ AIP.

Key words: Immunoglobulin G4, Immunoglobulin G4/immunoglobulin G ratio, Autoimmune pancreatitis, Pancreatic cancer, Cholangiocarcinoma