A rapid monoclonal antibody-based enzyme immunoassay (EIA) for the quantitative determination of soluble fibrin in...

Soluble fibrin is considered as a molecular marker for intravascular fibrin formation, and impending thrombotic events. Most of the existing assays are less suitable for routine clinical applications and their specificity may be limited. We have developed a sandwich-type EIA with a fibrin-specific MoAb described by us before (Proc Natl Acad Sci 1989; 86: 8951) as the capture antibody. An other MoAb (G8; Thromb Haemostas 1988; 60: 145) with an epitope in the carboxyl-terminal sections of the fibrin alpha-chains, was labeled with peroxidase and used as the tagging antibody. The EIA is calibrated against plasma spiked with known concentrations of soluble fibrin. The time-to-result of the EIA is only 1.5 h. Concentrations as low as 0.5 micrograms soluble fibrin/ml plasma are readily measureable. Heparin has no effect on the results. Fibrinogen and fibrin(ogen) degradation products are not detected. The values of fibrinopeptide A and soluble fibrin values found with the "COA-SET soluble fibrin" assay correlated well with the soluble fibrin values found with our EIA i.e. r = 0.998 and 0.984, respectively. The run-to-run variabilities were 7.9% and 6.6% for samples with low and high soluble fibrin concentrations, respectively. The within-run variabilities were 2.5, 1.8, 4.0 and 4.6% for samples with 1, 0.5, 0.25 and 0.125 micrograms soluble fibrin/ml, respectively. The sensitivity, specificity, accuracy and short time-to-result make our EIA suitable for routine clinical applications and the monitoring of the effectivity of heparinization.