A Comparative Study on Serum Immunoglobulin and Tumor Marker Levels in the Patients with Autoimmune Pancreatitis and Pancreatobiliary Malignancies / 대한소화기학회지

ABSTRACT

BACKGROUND/AIMS: Autoimmune pancreatitis (AIP) often occurs with obstructive jaundice in old age in cases of weight loss, mimicking pancreatobiliary cancer. This study aimed to determine the sensitivity and specificity serum IgG, IgG4 and CEA, CA 19-9 levels for the diagnosis of AIP and their ability to distinguish AIP from pancreatobiliary cancer. METHODS: The level of serums IgG, IgG4 and CEA, CA 19-9 were measured in 413 patients including 125 with AIP, 201 with pancreatic cancer, and 87 with cholangiocarcinoma. RESULTS: Among AIP patients, 43.2% (54/125) showed elevated IgG levels (> or =1,800 mg/dL) and 52% (65/125) showed elevated IgG4 levels (> or =135 mg/dL). Sensitivity and specificity of elevated serum IgG for diagnosis AIP were 43% and 88% respectively, and 52% and 97%, respectively for elevated serum IgG4. When the cut-off value of serum IgG4 was raised to 270 mg/dL (twice the upper limit of normal), the specificity improved to 100%. About 25% of the AIP patients showed an increased level of CA 19-9 at >37 U/mL and about 12.2% of them showed an increased level of CA 19-9 at >100 U/mL. On the contrary, only 1.8% of the AIP patients showed an increased level of CEA at >6.0 ng/mL. CONCLUSIONS: To avoid unnecessary surgeries resulting from a misdiagnosed pancreatobiliary cancer as opposed to AIP, it is necessary to consider both serum immunoglobulin and tumor marker. In particular, because high level of IgG4 (> or =270 mg/dL) and CA19-9 (>100 U/mL) are relatively rare in pancreatobiliary cancer and AIP, respectively, they will be helpful in differential diagnosis.