COMBINATION ASSAYS FOR IGG CLASS AND IGM CLASS ANTI-PYRUVATE DEHYDROGENASE COMPLEX (PDC)-E2 BY ELISA USING RECOMBINANT AUTOANTIGEN TO DIAGNOSE PRIMARY BILIARY-CIRRHOSIS

IgG and IgM class anti-pyruvate dehydrogenase complex (PDC)-E2 were st udied in sera from anti-M2-positive 84 patients with PBC by enzyme-lin ked immunosorbent assay (ELISA) to assess the usefulness of combinatio n assays. We used recombinant antigen coding the autoantigenic epitope s of PDC-E2 comprising the lipoic acid binding sites. Antigen specific ity of this ELISA was confirmed by inhibition test with pre-incubation of recombinant antigen with tested sera. Neither IgG class nor IgM cl ass anti-PDC-E2 could be detected in sera from healthy controls and pa tients with chronic liver diseases other than PBC. In 84 sera from pat ients with PBC, the positive rate of Ige class anti-PDC-E2 (66.7%) was almost the same as that of IgM class anti-PDC-E2 (65.5%). Seven sera were positive for IgG class anti-PDC-E2 but negative for IgM class ant i-PDC-E2. In contrast, six sera were positive for IgM class anti-PDC-E 2 but negative for Ige class anti-PDC-E2. In total, 62 (73.8%) of 84 s era were positive for IgG class and/or IgM class anti-PDC-E2. This rat e was higher than with assay of IgG class anti-PDC-E2 or IgM class ant i-PDC-E2 alone. The positive rate of IgG class and IgM class anti-PDC- E2s in sera with high AMA titers was higher than that in sera with low AMA titers. The sensitivity of ELISA matched that of immunoblotting i n 67 sera (79.7%). We conclude that the combination ELISAs for IgG cla ss and IgM class anti-PDC-E2 are useful for diagnosing PBC. (C) 1998 E lsevier Science Ireland Ltd. All rights reserved.