Immunoglobulin G4(+) B‐cell receptor clones distinguish immunoglobulin G 4‐related disease from primary sclerosing cholangitis and biliary/pancreatic malignancies

Immunoglobulin G4 (IgG4)‐related disease (IgG4‐RD) of the biliary tree and pancreas is difficult to distinguish from sclerosing cholangitis and biliary/pancreatic malignancies (CA). An accurate noninvasive test for diagnosis and monitoring of disease activity is lacking. We demonstrate that dominant IgG4(+) B‐cell receptor (BCR) clones determined by next‐generation sequencing accurately distinguish patients with IgG4‐associated cholangitis/autoimmune pancreatitis (n = 34) from those with primary sclerosing cholangitis (n = 17) and CA (n = 17). A novel, more affordable, and widely applicable quantitative polymerase chain reaction (qPCR) protocol analyzing the IgG4/IgG RNA ratio in blood also achieves excellent diagnostic accuracy (n = 125). Moreover, this qPCR test performed better than serum IgG4 levels in sensitivity (94% vs. 86%) and specificity (99% vs. 73%) and correlates with treatment response (n = 20). Conclusions: IgG4(+) BCR clones and IgG4/IgG RNA ratio markedly improve delineation, early diagnosis, and monitoring of IgG4‐RD of the biliary tree and pancreas. (Hepatology 2016;64:501‐507)