Anti GP2 IgA autoantibodies are associated with poor survival and cholangiocarcinoma in primary sclerosing cholangitis
Objective Pancreatic autoantibodies (PABs) comprising antibodies against glycoprotein 2 (anti GP2) are typically associated with complicated phenotypes in Crohn's disease, but have also been observed with variable frequencies in patients with UC. In a previous study, we observed a high frequency of primary sclerosing cholangitis (PSC) in patients with anti GP2 positive UC. We therefore aimed to characterise the role of anti GP2 in PSC. Design In an evaluation phase, sera from 138 well characterised Norwegian patients with PSC were compared with healthy controls (n=52) and patients with UC without PSC (n=62) for the presence of PABs by indirect immunofluorescence. Further, 180 German patients with PSC served as a validation cohort together with 56 cases of cholangiocarcinoma without PSC, 20 of secondary sclerosing cholangitis (SSC) and 18 of autoimmune hepatitis. Results Anti GP2 IgA specifically occurred at considerable rates in large bile duct diseases (cholangiocarcinoma=36% PSC and SSC about 50% In PSC, anti GP2 IgA consistently identified patients with poor survival during follow up (Norwegian/German cohort: p Log Rank=0.016/0.018) Anti GP2 IgA was associated with the development of cholangiocarcinoma in both PSC cohorts, yielding an overall OR of cholangiocarcinoma in patients with anti GP2 IgA positive PSC of 5.0 (p=0.001) Importantly, this association remained independent of disease duration, bilirubin level and age. Conclusions Anti GP2 IgA can be hypothesised as a novel marker in large bile duct diseases. In particular, in PSC, anti GP2 IgA identified a subgroup of patients with severe phenotype and poor survival due to cholangiocarcinoma. Anti GP2 IgA may therefore be a clinically valuable tool for risk stratification in PSC.
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