Hematological parameters influencing the Thrombostat 4000.

The effects of platelet counts, hematocrit, and leukocyte counts were studied on the closure times of the Thrombostat 4000 (in-vitro bleeding time, IVBT). Closure times became longer with platelet counts < 50 x 10(9)/L; an inverse linear correlation could be established. Hematocrit was also inversely correlated with the closure time. At constant platelet counts a hematocrit of 55% yielded an immediate closure of the filter, while with a hematocrit < 15% no closure times could be measured. At constant platelet counts and hematocrits, nomonuclear and polymorphonuclear leukocytes also influenced closure times; increased counts resulted in shorter closure times. Leukocytes from a patient with chronic myelocytic leukemia had the same effects.