[Anti-heparin/platelet factor 4 antibodies and heparin-induced thrombocytopenia--review]

Heparin-induced thrombocytopenia (HIT) is an antibody-mediated complication of heparin treatment that can lead to thrombosis and thromboembolism. HIT is mainly caused by immunoglobulin G (IgG) class among anti-heparin/platelet factor 4 antibodies that bind to epitopes on platelet factor 4 (PF4) released from activated platelets that developed when it forms complexes with heparin. Platelet aggregation and hypercoagulation status result from this process. Besides, the reactions between antibodies and vascular endothelial cells and monocytes are involved in HIT. Laboratory detection of anti-heparin/platelet factor 4 antibodies after heparin administration may help diagnose HIT early. Tests for detecting antibodies to the heparin/PF4 complex can be classified into functional platelet assays (which rely on the demonstration of platelet activation) and immunoassays (which detect the presence of an antibody without regard for its functional ability). But there is no simple and effective test available currently. In this article the anti-heparin/platelet factor 4 antibodies, pathogenesis of HIT, clinical laboratory assays and immunoassays are reviewed.