Serum Level of Ca 19-9 Increases Ability of IgG4 Test to Distinguish Patients with Autoimmune Pancreatitis from Those with Pancreatic Carcinoma

Background: Autoimmune pancreatitis (AIP) is often difficult to distinguish from pancreatic carcinoma or other pancreatobiliary diseases. High serum levels of carbohydrate antigen 19-9 (Ca 19-9) are indicative of malignancies, whereas high levels of immunoglobulin (Ig)G4 (>1.4 g/l) are characteristic of AIP. We investigated whether serum levels of these proteins can differentiate between these diseases. Methods: We measured levels of Ca 19-9 and IgG4 in serum samples from 33 patients with AIP, 53 with pancreatic carcinoma, an