The risk of major bleeding in patients with suspected heparin-induced thrombocytopenia

Background: The presence of a hypercoagulable disorder such as heparin-induced thrombocytopenia (HIT) may protect against anticoagulant-associated bleeding. Objectives: To determine the incidence of major bleeding in patients with suspected HIT. Methods: We performed a retrospective analysis of 310 patients suspected of having HIT from the Hospital of the University of Pennsylvania and an affiliated community hospital. We compared the cumulative incidence of major bleeding following suspicion for HIT by ultimate HIT status (HIT+ or HIT−) and exposure to an alternative anticoagulant (Tx+ or Tx−). Secondary outcomes included the incidence of new/progressive thrombosis and 30-day mortality. Results: The incidence of major bleeding was high in the HIT+Tx+, HIT− Tx+, and HIT−Tx− groups (35.7%, 44.0%, and 37.3%, respectively). The time to first major bleeding event did not differ between groups (P =.24). Factors associated with increased risk of major bleeding included intensive care unit admission (HR 2.24, 95% CI 1.44-3.47), platelet count < 25 × 10⁹/L (HR 2.13, 1.10-4.12), and renal dysfunction (HR 1.56, 1.06-2.27); 35.7% of HIT+Tx+, 13.8% HIT−Tx+, and 9.3% of HIT−Tx− patients experienced new or progressive thrombosis. Mortality was similar among the three groups (26.2% HIT+Tx+, 34.5% HIT−Tx+, and 26.7% of HIT−Tx− [P =.34]). Conclusions: Among patients with suspected HIT, major bleeding was common regardless of HIT status. Contrary to our hypothesis, HIT+ patients were not protected from major bleeding. A better understanding of bleeding risk is needed to inform management decisions in patients with suspected HIT.