Clinical usefulness of serum immunoglobulin G and G4 level in the diagnosis of autoimmune pancreatitis

Abstract

BACKGROUND/AIMS: To diagnose autoimmune pancreatitis (AIP), serum IgG and IgG4 concentration are significant serologic markers. The purpose of this study was to assess the utility of serum IgG and IgG4 for the diagnosis of AIP. METHODS: We divided enrolled patients into 2 groups: autoimmune pancreatitis and other pancreatic disease. We measured serum IgG and IgG4 levels in patients including 12 AIP and 23 other pancreatic disease. RESULTS: Among AIP patients, 10 cases (83%) showed elevated IgG4 levels of more than 135 mg/dL and 4 cases (33%) showed elevated IgG levels of more than 1,800 mg/dL, the current cutoff value applied in Japan. Only one patient showed elevated serum IgG level, despite having normal IgG4 level. Sensitivity and specificity for AIP of elevated serum IgG4 (>135 mg/dL) were 91% and 92%, and for elevated serum IgG (>1,800 mg/dL) 67% and 92%, respectively. The optimal cut-off level of IgG4 using receiver operation characteristic (ROC) was 127 mg/dL, at which the sensitivity and specificity were 83% and 96%, respectively, for the diagnosis of AIP. Serum IgG at 1,520 mg/dL showed the sensitivity and specificity of 83% and 87%, respectively. CONCLUSIONS: The measurement of serum IgG and IgG4 are helpful to diagnose AIP. Serum IgG and IgG4 are complementary to each other in the diagnosis of AIP.