Abstract
In four patients with hereditary protein C (PC) deficiency and 30 under stabilized warfarin therapy, plasma levels of PC were measured by an enzyme-linked immunosorbent assay (ELISA) using a monoclonal anti-PC antibody which recognizes a Gla-domain-related conformational change. The results were compared with those obtained by other methods (polyclonal ELISA, amidolytic and anticoagulant assays). Gla-PC levels measured by the monoclonal ELISA were very close to PC values obtained by other assays in patients with hereditary PC deficiency. In patients under stable warfarin therapy, each assay gave different PC values. The mean plasma level of total PC antigen measured by the polyclonal ELISA was 58.5±11.0%, Gla-PC antigen 35.3±13.0%, amidolytic activity 60.6±12, 4%, and anticoagulant activity 14.8±7.4%. Among these, anticoagulant activity and Gla-PC antigen correlated well with thrombotest values, prothrombin activity and factor X activity. These results indicate that the present monoclonal ELISA (Gla-PC) measures PC specifically, and that Gla-PC assay as well as anticoagulant assay can evaluate the physiological PC function in patients during oral anticoagulant therapy.
