Immunologic quantification of fibrin deposition in thrombi formed in flowing native human blood

We describe a new method for quantification of fibrin in thrombi formed in native human blood at venous and arterial shear conditions in a parallel-plate perfusion chamber device. Thrombi consisting of various proportions of fibrin and platelets were digested by plasmin. Fibrin deposition (μg/cm²) was calculated from the measured D-dimer levels.

Fibrin deposition in thrombi formed on a tissue factor (TF)-rich surface increased with increasing shear rate from 37 μg/cm² at 100/s to 77 μg/cm² at 2600/s (significant at 95%, ANOVA). The plasma levels of thrombin–antithrombin III complexes (TAT) increased in concert. In contrast, fibrin deposition in thrombi formed on collagen fibrils and the corresponding TAT plasma levels were independent of the shear rate and much lower than those elicited by the TF-rich surface (significant at 95%, ANOVA). The intra-individual variation in fibrin deposition was on average 10%, whereas the inter-individual differences were >500%. Such a large inter-individual difference has not been detected by morphometry which usually is employed in similar studies.

The present method is more accurate and less time-consuming than the morphometric approach. The novel method measures fibrin on the surface and in and around the thrombi, thus total deposited fibrin. In contrast, the morphometry approach quantifies surface coverage with fibrin only, thus being semiquantitative at best.