Abstract: 332.ANTICOAGULATION AND ANTITHROMBOTIC THERAPY | NOVEMBER 5, 2020 Admission Rothman Index, Aspirin, and Intermediate Dose Anticoagulation Effects on Outcomes in COVID-19: A Multi-Site Propensity Matched Analysis *,2 1 George Goshua, MD, Yiwen Liu, *,4 Rebecca Fine, MD, Kejal Amin, PharmD, *,8 Dayna McManus, PharmD, *,10 Chaar, MD, Matthew L. Meizlish, MSc, Eric Chang, MD, Adina Petrosan, PharmD, Hyung J. Chun, MD, 2 *,5 *,11 *,9 *,6 *,3 *,7 Yuxin Liu, MD, Cassius Ilya Ochoa *,12 Nicholas A. Defilippo, PharmD, S. Neuberg, ScD, Kent A. Owusu, PharmD, *,13 Donna Alfred Ian Lee, MD PhD 14 1 Section of Hematology, Yale University School of Medicine, New Haven, CT 2 Department of Data Science, Dana-Farber Cancer Institute, Boston, MA 3 Yale University School of Medicine, New Haven, 4 Department of Internal Medicine, Yale University School of Medicine, New Haven, 5 Department of Pharmacy, Yale-New Haven Hospital, New Haven, 6 Section of Hematology, Yale University School of Medicine, New Haven, 7 Yale University, New Haven, CT 8 Department of Pharmacy, Yale University School of Medicine, New Havem, 9 Department of Pharmacy, Yale New Haven Hospital, New Haven, 10 Yale School of Medicine, New Haven, CT 11 Department of Medicine, Section of Cardiovascular Medicine, Yale University School of Medicine, New Haven, CT 12 University of Connecticut, Storrs, 13 Yale New Haven Hospital, New Haven, CT 14 Section of Hematology, Department of Internal Medicine, Yale University School of Medicine and Yale Cancer Center, New Haven, CT Blood (2020) 136 (Supplement 1) : 23. http://doi.org/10.1182/blood-2020-143349 Introduction: Venous thromboembolism and in-situ small vessel thrombosis are increased in hospitalized patients with COVID-19 in several patient cohorts. Endotheliopathy and activation of both platelets and coagulation predict critical illness and death. For these reasons the use of anti-platelet agents and increased-intensity anticoagulation in the care of hospitalized patients with COVID-19 is under intense study in several clinical trials. We sought to examine the impact of aspirin and anticoagulation on hospitalization outcomes. Methods: We examined outcomes in a large multi-site cohort of consecutive, hospitalized, COVID-19 laboratory confirmed patients under a risk-stratified treatment algorithm from March 13 through June 18, with a focus on efficacy of aspirin and/or increased-intensity anticoagulation. Out of 4150 identified hospitalized patients with COVID-19, we created 3 study cohorts. The overall cohort (2785 patients) excluded pediatric patients, those with incomplete electronic data, and those with multiple admissions. The aspirin (1956 patients) and anticoagulation (1623 patients) cohorts were nested within the overall cohort; the former excluded patients on any home anti-platelet therapy or those who received non-aspirin anti-platelet therapy in the hospital, while the latter excluded patients who did not receive prophylactic or intermediate dose anticoagulation in the hospital. The primary outcome was in-hospital death. Secondary outcomes were time-to-death with a competing risk (time-to-hospital-discharge), escalation to ICU, length-of-stay and use of mechanical ventilation. Variables examined included age, gender, BMI, race, Rothman Index (RI), D-dimer (DD) and patient co-morbidities including cardiovascular disease, chronic kidney disease, and prior VTE. The aspirin and anticoagulation..