The effect of fibrin polymerization inhibitors on quantitative measurements of plasma fibrinogen

Abstract

A number of reports have highlighted discrepancies between the DuPont aca and fibrometer-based methods for quantitating plasma fibrinogen levels. Although many authors have suggested that the presence of fibrin(ogen) degradation products are in some way responsible for the discrepancies, no direct test of this hypothesis has been carried out. In this report, the authors demonstrate that inhibitors of fibrin monomer polymerization have different effects on the aca and fibrometer assays of fibrinogen. Fibrin polymerization inhibitors allow short soluble fibrin polymers to assemble that can scatter light and are therefore detected by the aca method. However, these short polymers do not gel and thus are not detected by the fibrometer. Therefore, the fibrometer method gives lower fibrinogen values than the aca in the presence of fibrin polymerization inhibitors. The authors also assayed plasma from a patient whose fibrinogen did not polymerize normally and therefore was not measurable by the fibrometer assay. The dysfibrinogenemic plasma assayed by the aca method recorded normal fibrinogen levels. In conclusion, the DuPont aca fibrinogen assay is insensitive to alterations of fibrin polymerization whether from inhibitors or a defective fibrinogen molecule.