Anti-mitochondrial antibodies (AMA) occur in over 95% of PBC cases and are absent in patients with extrahepatic biliary obstruction as well as in other liver diseases.

The presence of AMA in greater than 95% of patients with PBC and their virtual absence in extrahepatic jaundice makes detection of these antibodies extremely valuable in establishing a differential diagnosis. AMA can be detected by IFA on mouse kidney/stomach substrate, or by ELISA.

In addition to AMA, patients with PBC have autoantibodies to two other nuclear antigens: Gp-210 and Sp-100. 28% to 52% of PBC patients have antibodies to nuclear pore complex protein Gp-210, characterized by peripheral staining of the nucleus by indirect IFA.

Anti-Sp-100 antibodies are characterized by multiple nuclear dot staining of the nucleus. These antibodies are present in approximately 30% of patients with PBC. Approximately one half of AMA negative PBC patients are positive for antibodies to Gp-210 and Sp-100.