Characterization of M2 antibodies in asymptomatic Chinese population.

Aim: To investigate the presence of M2 antibodies specific for primary biliary cirrhosis (PBC) in asymptomatic Chinese and identify patients with early PBC.

Methods: Enzyme-linked immunosorbent assay (ELISA) tests for M2 antibodies to recombinant protein were performed in 5 011 subjects (age range, 26-85 years; mean age: 45.81+/-15.02 years) who took an annual physical examination. M2-positive subjects were further analyzed for immunoglobulin (Ig) classes and subclasses of M2 antibodies. Clinical, biochemical and immunological data were obtained for M2-positive subjects. In addition, ultrasonography (US) or endoscopic retrograde cholangio-pancreatography (ERCP) was performed to exclude any disorders other than PBC.

Results: M2 antibodies were detected in 8 (0.16 %) of the 5 011 subjects studied. Of the 8 subjects, 7 were female and 1 was male (age range: 40-74 years). An unexplained increase of serum alkaline phosphatase (ALP) and gamma glutamyl transpeptidase (gamma-GT) values, often to striking levels, was detected in 4 M2-positive subjects, 3 of them accorded with the diagnostic criteria recommended by the American Association for the Study of Liver Diseases, even though they had no symptoms of PBC (such as fatigue, pruritus or jaundice). Liver biopsy was performed in two M2-positive subjects and the histology was compatible with PBC in both cases.

Conclusion: Our data, while not assessing the true prevalence of asymptomatic PBC in the general population, suggest that asymptomatic PBC is much more common in China than has been supposed.