Is prior antithrombotic use protective against COVID-19 infection? A cross-sectional study of the University of California Health patient population

© Annals of Blood. All rights reserved. Ann Blood 2022 | https://dx.doi.org/10.21037/aob-21-75 As COVID-19 infection rates rise worldwide and hospital capacities fall nationwide, increased attention is focused on determining who is most at risk for severe disease (1). While some patients are asymptomatic or have mild symptoms when diagnosed with a COVID-19 infection, those who are older, males, or have pre-existing comorbidities (obesity, cardiovascular disease, diabetes, or pulmonary disease) are at increased risk of severe COVID-19 and have higher mortality rates (2). This population overlaps significantly with patients who are taking antithrombotics; since they are typically older and have comorbidities (coronary artery disease, atrial fibrillation, venous thromboembolism, cerebral vascular attack, or peripheral artery disease) that further increase their risk of severe COVID-19. COVID-19 has been associated with a prothrombotic state, leading to increased risk of microvascular thrombosis, arterial, or venous thromboembolic disease. In critically ill patients, in addition to causing acute respiratory distress syndrome, COVID-19 results in a hypercoagulable state, with extensive thrombosis of the small vessels of the lungs, causing diffuse alveolar damage, and extrapulmonary organs (3,4). Coagulation factor X (FX) is a serine protease that is synthesized by the liver, with increased levels reported in patients with cardiopulmonary disease. Interestingly, these FX levels have resulted in an increased tendency to have higher infection rates, increased coagulation and inflammation activation, and fibrosis development (2). Over the past year, preliminary observations on anticoagulant therapy show an association with better outcomes in moderate and severe COVID-19 patients who require mechanical ventilation and have signs of coagulopathy. The use of various regimens of antithrombotics in disease management has been implemented; however, the benefit of prior use of antithrombotic medications has not been fully elucidated. We investigate whether patients with prior antithrombotic use for pre-existing conditions influences COVID-19 infection rates or disease mortality in a California-based population. This cross-sectional study utilized the University of California COVID-19 Research Data Set (UC CORDS), a HIPAA-limited database of medical records for patients tested for COVID-19 across UC medical centers (5). Information regarding patient demographics, COVID-19 testing results, and mortality rates after COVID-19 testing Letter to the Editor