Enzyme-linked immunosorbent assay of human factor VII based upon a monoclonal antibody that recognizes the native conformation of the protein.

An enzyme-linked immunoassay (ELISA) was developed for measuring human factor VII antigen using two monoclonal antibodies, one of them reacting only with fully carboxylated factor VII. This assay permits to measure factor VII antigen in concentrations ranging from 0.78 to 100 ng/ml, with within- and between-assay coefficients of variation of less than 7%. In 53 normal subjects, 32 patients with liver cirrhosis, 21 pregnant women and 53 patients on oral anticoagulant therapy the plasma levels of FVII antigen were very similar to those of factor VII coagulant activity measured with a bioassay. The ELISA also gave very similar values of factor VII antigen in plasma and in serum, and in plasma before and after exposure to cold, indicating that the assay is not affected by factor VII activation. In five of 8 patients with severe congenital deficiency of factor VII values of factor VII antigen were higher than those of factor VII activity. The close concordance of factor VII values obtained by ELISA and bioassay in the majority of plasmas, including those from patients on oral anticoagulant therapy, indicates that the assay measures native factor VII and can perhaps replace the bioassay systems in clinical conditions associated with normal or high levels of factor VII.