The laboratory diagnosis and clinical management of patients with heparin-induced thrombocytopenia: an update.

Heparin-induced thrombocytopenia (HIT) is a serious adverse effect of heparin exposure that can progress to severe thrombosis, amputation, or death. HIT is an immune response in which antibodies cause platelet activation, platelet aggregation, the generation of procoagulant platelet microparticles, and activation of leukocytes and endothelial cells. Early diagnosis based on a comprehensive interpretation of clinical and laboratory information is important to improve clinical outcomes. However, limitations of the laboratory assays and atypical clinical presentations can make the diagnosis difficult. Clinical management of patients with HIT is with a non-heparin anticoagulant such as a direct thrombin inhibitor or danaparoid followed by a vitamin K antagonist for long-term treatment. The new anti-factor Xa drugs (fondaparinux, rivaroxaban, apixaban) and other non-heparin antithrombotic agents can potentially be used for the treatment of HIT if clinically validated. Important drug-specific limitations and dosing and monitoring guidelines must be respected for patient safety. Issues still exist regarding the optimal clinical management of HIT.