Filter bleeding time: A new in vitro test of hemostasis II. Application to the study of von willebrand disease and platelet function inhibitors

Abstract

The effect of platelet function inhibitors and von Willebrand (vW) disease on hemostasis was evaluated with a new method, the Filter Bleeding Time (FBT) test which does not require a skin incision. This method is based on the progressive slowing of blood flow associated with plugging of a woven Dacron filter by platelet clumps during passage of blood through the filter. Antiplatelet agents studied were acetyl salicylic acid (ASA), prostaglandin I 2 (PGI 2), and a thromboxane synthetase inhibitor, UK-37, 248-01 (UK). Parameters measured were FBT (time required for the drop rate interval to exceed 30 sec), bleeding volume (BV; total number of drops in FBT), initial bleeding rate (IBR; number of drops during the first minute), and percent platelet count reduction (PCR) during passage of blood through the filter. ASA (650 mg p.o. in normal human subjects) caused an increase in FBT from 4.94±2.97 ( x ±SD) to 10.28±3.27 min (p = 0.003) and BV (34±19 to 69±31 drops, p = 0.01), and a decrease in PCR (29.4±7 to 12.5±2%, p = 0.006). PGI p (0.1 uhf added to normal human blood) caused an increase in,FBT (4.76±2.33 to 14.44±3.39, p = 0.0006) and BV (41±18 to 94±35, p = 0.001) and a decrease in PCR (29.6±6.4 to 7.1±7.8, p = 0.004). IBR did not change significantly in these studies. UK (3 mg/kg p.o. in normal dogs) caused no significant change in any of these parameters despite the drug's inhibition of platelet aggregation by ADP and collagen. Values in 4 pigs with vW disease were abnormal compared to normal pigs: FBT, 23.83±20.47 vs 5.09 min, p = 0.04; BV, 168±154 vs. 30±24 drops, p = 0.04; PCR, 7.1±1.0 vs 28.5±10.7%, p = 0.002; and IBR, 29.7±7 vs. 10±6 drops/min, p = 0.002. These studies suggest that IBR is a measure of platelet adhesion, while FBT, BV and PCR reflect the totality of platelet reactions including platelet adhesion and aggregation. FBT is considered useful in the study of the mechanisms and efficacy of platelet function inhibitors, and in the investigation of platelet disorders.