| Abstract: | Platelets contain heparin neutralizing activity, which is released into plasma following aggregation. This material is probably identical to platelet factor 4. We describe a technic to measure heparin neutralizing activity in platelet-poor plasma based on the serial heparin dilution technic of Harada and Zucker. Heparin neutralizing activity was depressed in thrombocytopenia due to immune thrombocytopenia and bone marrow depression, and elevated in thrombocytopenia due to disseminated intravascular coagulation. Secondary thrombocytosis is characterized by markedly elevated heparin neutralizing activity, while thrombocytosis associated with myeloproliferative disorders has normal heparin neutralizing activity. |
