Clinical evaluation of a new test of hemostasis: The filter bleeding time

Abstract The clinical value of a new in vitro test of hemostasis, which we have called Filter Bleeding Time (FBT), was determined in 59 patients referred because of a suspected bleeding disorder. FBT is based on the progressive slowing of the drop rate of citrated blood through a filter of woven Dacron under constant pressure as platelet aggregates occlude the filter. The value for FBT is defined as the time when the blood drop interval has reached 1 minute. The Mayo modification of the Ivy bleeding time (IBT) was performed in all patients; platelet response to ADP, collagen, epinephrine and arachidonate was performed in 24 patients. In 30 normal volunteers FBT measured 1–3 hr after venipuncture was 2.8±1.5 (×-±1SD) min. The FBT was prolonged in 3 of 3 patients with Glanzmann's thrombasthenia, 2 with disseminated intravascular coagulation, 1 with chronic lymphocytic leukemia, 1 with myelofibrosis, and 1 who had taken aspirin. In 6 patients FBT was prolonged while IBT was normal: 4 after taking aspirin, 2 with polycythemia vera. All 6 had reduced platelet aggregation (PA) to ADP (5 μM), collagen (2 mg/ml), epinephrine (5 μM) and/or arachidonate (1.7 μM). In 3 patients FBT was normal while IBT was abnormal: 1 with disseminated intravascular coagulation, 2 undiagnosed; 1 of these 3 had abnormal PA. Of 6 patients with von Willebrand's disease, FBT was prolonged in 5 and borderline in 1; IBT was prolonged in 3, normal in 1, and not done in 2 infants. In 3 patients (1 with myelofibrosis, 1 with collagen disease, 1 with renal insufficiency) IBT could not be determined or was considered invalid due to an abnormality of the skin and/or subcutaneous hematoma; in these patients, FBT and PA were both abnormal. FBT was normal in six patients with hemophilia tested. FBT appears to be highly reproducible and more sensitive than IBT in the detection of disorders of hemostasis involving platelets.