Evaluation of platelet function by filter bleeding time.

Currently we developed a new in vitro test of hemostasis, the filter bleeding time (FBT), which is based on progressive decrease of flow rate of citrated blood through a disk filter of Woven Dacron under controlled pressure as platelet aggregates occlude the filter. FBT is defined as the time when the blood drop rate has fallen to less than 1/30sec. There was a high correlation (r=-0.91) between FBT and platelet count below 105/μl in dogs made thrombocytopenia by estradiol. There was a significant correlation (r=0.65) between FBT and Ivy Bleeding Time (IBT) in 59 patients referred because of a suspected bleeding disorder. FBT was prolonged in 3 of 3 patients with Glanzmann's thrombasthenia, 5 of 6 with von Willebrand disease and normal in 6 of 6 with hemophilia. FBT was more sensitive than IBT in detecting abnormal platelet aggregation in response to collagen, epinephrine or arachidonate. A monoclonal platelet antibody (HP1-1D), which is a specific antibody for platelet membrane glycoprotein IIb and IIIa, increased FBT in a dose dependent manner. FBT was prolonged by adding 0.1μM prostaglandin I2 and an ADP scavenge system, CP/CPK/ATP but not by adding thromboxane synthetase inhibitor, UK-37, 248 or UK-38, 485. Thromboxane synthetase inhibitors had, however, a synergistic effect on FBT when added with CP/CPK/ATP. Oral ticlopidine 250mg b. i. d. for 7 days increased FBT as well as IBT and Template bleeding time. Additional increase in FBT and skin bleeding times was produced by simultenous taking of 650mg aspirin b. i. d. for 7 days.FBT was significantly shorter in smokers than in non-smokers. It is suggested from these observations that FBT is a useful test of platelet function and has certain advantages over skin bleeding time methods.