title: [Heparin-induced thrombocytopenia].
abstract: Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction that carries an increased risk of thromboembolic complications. HIT is caused by platelet-activating antibodies directed against a complex of platelet factor 4 (PF4) and heparin. HIT typically manifests in the second week after initiation of heparin therapy with a platelet count reduction of more than 50% of the highest level after the start of heparin administration as well as thromboembolic events. The clinical probability can be calculated by the 4 T's score. The laboratory diagnosis of HIT is based on confirmation of PF4/heparin antibodies or on functional tests that provide evidence of heparin-dependent platelet-activating antibodies. A low 4 T's score and negative HIT test virtually rule out the presence of HIT. Patients with acute HIT require anticoagulation with a compatible anticoagulant in a therapeutic dose. The drugs currently available for this include the direct thrombin inhibitors argatroban, lepirudin, bivalirudin, and desirudin and the indirect factor Xa inhibitors danaparoid and fondaparinux.
authors.affiliation: Institut für Immunologie und Transfusionsmedizin, Ernst-Moritz-Arndt Universität, Sauerbruchstraße, 17489 Greifswald, Deutschland.
authors.forename: T
authors.initials: T
authors.lastname: Thiele
authors.forename: K
authors.initials: K
authors.lastname: Althaus
authors.forename: A
authors.initials: A
authors.lastname: Greinacher
mesh_terms: D000208:Acute Disease; D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D001323:Autoantibodies / Q000097:blood; D006493:Heparin / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D010972:Platelet Activating Factor / Q000502:physiology; D010976:Platelet Count; D010978:Platelet Factor 4 / Q000276:immunology; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000276:immunology
chemical_list: D000925:Anticoagulants; D001323:Autoantibodies; D010972:Platelet Activating Factor; D010978:Platelet Factor 4; D006493:Heparin