Impact of Baseline Thrombocytopenia on Early Outcomes in Patients With Acute Venous Thromboembolism.

Managing acute venous thromboembolism (VTE) in patients with thrombocytopenia is challenging. We used data from the RIETE registry to investigate the impact of baseline thrombocytopenia on early VTE-related outcomes, depending on the initial presentation as pulmonary embolism (PE) or isolated lower-limb deep vein thrombosis (DVT). From March 2003 to November 2022, 90 418 patients with VTE were included. Thrombocytopenia was categorized as severe (< 50 000/μL, n = 303) or moderate (50 000-99 999/μL, n = 1882). The primary outcome, fatal PE within 15 days after diagnosis, and secondary outcomes, including major bleeding and recurrent VTE, were analyzed using multivariable-adjusted models. Among 52 703 patients with PE, the 15-day case-fatality rates from PE were 5.8% for severe thrombocytopenia, 4.5% for moderate thrombocytopenia, and 1.1% for normal platelet counts. In 37 715 patients with isolated DVT, the cumulative incidence of fatal PE were 0, 0.2%, and 0.05%, respectively. Multivariable analysis revealed a five-fold increase in the risk for fatal PE in severe thrombocytopenia (adjusted HR: 4.89; 95%CI: 2.55-9.39) without significant differences between severe and moderate thrombocytopenia. Thrombocytopenia, either moderate or severe, was also associated with increased risk for both, major bleeding and recurrent VTE at 15 days. Initial presentation with PE substantially worsened prognosis compared to isolated DVT. In conclusion, in patients with acute VTE, thrombocytopenia at baseline was associated with increased risk of early death from PE, a finding that was driven by the subgroup whose initial presentation was PE.