Heparin-induced Thrombocytopenia: A Narrative Review of Clinical Implications

Heparin-induced thrombocytopenia is a rare immune-mediated complication of heparin therapy, characterized by a decrease in platelet count by more than 50% of the baseline. Typically occurs between 5 to 10 days after the initiation of heparin. Incidence in the United States ranges from 0.2% to 3.0%, depending on the population studied and the diagnostic criteria used. HIT has been categorized into two types: HIT type I and II. While HIT type I is a benign, non-immune mediated response presenting with mild self-limited thrombocytopenia, HIT type II is a severe, immune-mediated, potentially fatal complication that requires urgent diagnosis and management. Moreover, Type II is the most common form of HIT. Signs and symptoms may include a sudden onset of pain, redness, and swelling or ecchymosis in extremities. For diagnosis, the 4Ts score is a widely used clinical scoring system that can help assess the probability of HIT based on the timing of thrombocytopenia onset, degree of thrombocytopenia, presence of thrombosis, and other clinical factors. Diagnostic confirmation can be pursued with the help of immunoassays or functional assays such as ELISA and/or SRA. The first step in managing HIT is to discontinue all heparin exposure. Secondly, non-heparin anticoagulation medication must be initiated quickly. As a final step, it may be necessary to switch from parenteral to oral anticoagulation following the resolution of HIT.