An Algorithm for “Indeterminate” Test Results in the Platelet Serotonin Release Assay for Heparin-Induced Thrombocytopenia (HIT).

Abstract HIT is a prothrombotic complication of heparin caused by antibodies that recognize complexes of platelet factor 4 (PF4) bound to heparin or certain other polyanions. These antibodies produce thrombocytopenia by activating platelets via their Fc receptors. A “functional” (platelet activation) assay that utilizes washed platelets, known as the 14C-serotonin release assay (SRA), has the highest reported …