Prophylactic Anticoagulation and Thrombosis in Hospitalized Patients with Clinically Stable COVID-19 at Admission: From the CLOT-COVID Study

Background: The potential benefit of routine prophylactic anticoagulation for all hospitalized patients with clinically stable coronavirus disease 2019 (COVID-19) is still controversial. We aimed to evaluate prophylactic anticoagulation and thrombosis in hospitalized patients with clinically stable COVID-19.Methods: The CLOT-COVID Study was a multicenter observational study enrolling 2894 consecutive hospitalized patients with COVID-19. The current study population consisted of 1738 hospitalized patients with mild COVID-19 at admission not requiring oxygen administration, who were divided into 2 groups; patients with prophylactic anticoagulation (N=326) and those without (N=1412).Results: Patients with prophylactic anticoagulation more often had several comorbidities, and had more severe status of the worst severity of COVID-19 during hospitalization compared with those without (Mild: 38% versus 82%, Moderate: 55% versus 17%, and Severe or death at discharge: 6.4% versus 0.7%, P<0.001). During hospitalization, 8 patients (0.5%) developed thrombosis, and the incidences of thrombosis were numerically higher in patients with more severe status of worst severity of COVID-19 during hospitalization (Mild: 0.2%, Moderate: 1.2% and Severe or death at discharge: 3.2%). Among 1280 patients who did not worsen in COVID-19 severity, 2 patients developed thrombosis with relatively high D-dimer levels at admission (4.6 and 15.0 μg/mL, respectively).Conclusions: Among hospitalized patients with clinically stable COVID-19 at admission, patients who did not worsen in COVID-19 severity after admission rarely developed thrombosis, although patients with worsening of COVID-19 severity after admission more often received prophylactic anticoagulation and might have a higher risk of thrombosis.