Introduction: Heparin-induced thrombocytopenia (HIT) is a drug-mediated, prothrombotic disorder caused by immunization against platelet factor 4 (PF4) after complex formation with heparin or other polyanions. A subset of anti-PF4/heparin antibodies are capable of intravascular platelet activation by cross-linking Fcgamma receptor IIA leading to platelet count decrease and/or thrombosis. HIT can be potentially associated with devastating complications such as life-threatening thrombosis making it one of the most serious adverse drug reactions. Diagnosis of HIT based on clinical information is often difficult.
Area covered: This review highlights the pathophysiology of HIT, emphasizing characteristic clinical features and the role of laboratory assays in the diagnosis of HIT. In addition, a summary of current therapeutic options for patients with HIT will be provided.
Expert opinion: A combination of clinical pretest scoring system and laboratory investigation is usually necessary to diagnose HIT. If HIT is strongly suspected, all sources of heparin must be stopped and an alternative non-heparin anticoagulant should be started to prevent new thromboembolic complications. However, heparin alternative anticoagulants bear a considerable bleeding risk, especially if given to patients with thrombocytopenia due to other reasons than HIT. A better understanding of clinical and laboratory features of HIT may help developing strategies to avoid complications induced by this serious adverse reaction against heparin.
Keywords: Antibody; heparin; thrombocytopenia; thrombosis.