IMMUNOLOGICAL QUANTIFICATION OF FIBRIN DEPOSITION IN THROMBI FORMED IN FLOWING NATIVE HUMAN BLOOD

We describe a new method for quantification of fibrin in thrombi forme d in native human blood at venous and arterial shear conditions in a p arallel-plate perfusion chamber device. Thrombi consisting of various proportions of fibrin and platelets were digested by plasmin. Fibrin d eposition (mu g/cm(2)) was calculated from the measured D-dimer levels . Fibrin deposition in thrombi formed on a tissue factor (TF)-rich sur face increased with increasing shear rate from 37 mu g/cm(2) at 100/s to 77 mu g/cm(2) al 2600/s (significant at 95%, ANOVA). The plasma lev els 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 (signif icant at 95%, ANOVA). The intra-individual variation in fibrin deposit ion 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 pres ent method is more accurate and less time-consuming than the morphomet ric approach. The novel method measures fibrin on the surface and in a nd around the thrombi, thus total deposited fibrin. In contrast, the m orphometry approach quantifies surface coverage with fibrin only, thus being semiquantitative at best.