Real-world study examines relative risk of thromboembolic events resulting from COVID-19 as compared with influenza

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Thought Leadership  |  01 February 2022

In a study conducted by scientists at HealthPals, Stanford University, and Veradigm®, COVID-19 was independently associated with a higher 90-day risk for venous thrombosis, but not arterial thrombosis, as compared with influenza.1

This large retrospective cohort study utilized the Veradigm Health Insights Ambulatory EHR (HIAE) Research Database linked with insurance claims data. The EHR dataset consists of de-identified patient records sourced from ambulatory/outpatient primary care and specialty settings. The insurance claims data contain a de-identified combination of closed and open claims from inpatient and outpatient locations.

Researchers evaluated a COVID-19 cohort with over 417,000 patients (median age 57 years, 61% women) and a comparison influenza cohort with over 345,000 patients (median age 47 years, 66% women) for thromboembolic events in the 90 days following infection. Compared with influenza patients, and after accounting for baseline cohort characteristics, patients with COVID-19 had significantly higher risk for venous thrombosis but not for arterial thrombosis.

During the early period of the pandemic, several studies suggested SARS-CoV-2 infection was a risk factor for myocardial infarction and ischemic stroke, pulmonary embolism, and thromboembolic events, leading to substantial interest in the role of thromboprophylaxis in COVID-19 management.2-5 However, these initial analyses were limited by largely case series-based or single-arm designs or by a failure to adjust broadly for baseline cohort characteristics that could affect thromboembolic outcomes. In addition, early studies focused primarily on inpatient populations with COVID-19. Accurately assessing the thromboembolic risks of SARS-CoV-2 infection is essential to inform the potential benefits and risks of thromboprophylaxis in treating COVID-19.

To date, this study is the first and largest cohort study to quantify the independent thromboembolic risk of COVID-19 compared with influenza after adjusting broadly for baseline cohort characteristics in a largely outpatient cohort. The authors conclude that this study warrants expedited prospective validation to help clarify the precise nature of arterial and venous thromboembolic risks in COVID-19 and, thus, the role of thromboprophylaxis in COVID-19 management.

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  1. Ward A, Sarraju A, Lee D, et al. COVID-19 is associated with higher risk of venous thrombosis, but not arterial thrombosis, compared with influenza: Insights from a large US cohort. Pre-print. 2021;doi:
  2. Katsoularis I, Fonseca-Rodríguez O, Farrington P, Lindmark K, Connolly A-MF. Risk of acute myocardial infarction and ischaemic stroke following COVID-19 in Sweden: a self-controlled case series and matched cohort study. Lancet. August 14, 2021;398(10300):599-607. doi:doi: 10.1016/S0140-6736(21)00896-5.
  3. Jevnikar M, Sanchez O, Chocron R, et al. Prevalence of pulmonary embolism in patients with COVID-19 at the time of hospital admission. Eur Respir J. July 20, 2021;58(1):2100116. doi:10.1183/13993003.00116-2021.
  4. Bilaloglu S, Aphinyanaphongs Y, Jones S, Iturrate E, Hochman J, Berger JS. Thrombosis in Hospitalized Patients With COVID-19 in a New York City Health System. JAMA. 2020;324(8):799-801. doi:10.1001/jama.2020.13372.
  5. Merkler AE, Parikh NS, Mir S, et al. Risk of Ischemic Stroke in Patients With Coronavirus Disease 2019 (COVID-19) vs Patients With Influenza. JAMA Neurol. 2020;77(11):1366-1372. doi:10.1001/jamaneurol.2020.2730.
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