DSEN Abstract
Risk of arterial and venous thromboembolism events among patients with COVID-19: A multi-national collaboration of regulatory agencies from Canada, Europe, and US

A study conducted by the Canadian Network for Observational Drug Effect Studies (CNODES)

Summary and Key Messages

The risk of ATE and VTE among patients diagnosed with COVID-19 varied by country.
This variation was observed among patients initially diagnosed in the ambulatory setting and the hospital setting, and before and during COVID-19 vaccine availability.
Differences in healthcare systems, data sources, prevalence of underlying comorbid conditions, and approaches to COVID-19 and thromboembolism case definition may have contributed to the variation in thromboembolism risk estimates observed between countries.

Project Lead & Team

This research was funded by CIHR – Drug Safety and Effectiveness Network and conducted by CNODES.

For more information, please contact info@cnodes.ca.

What is the issue?

Cohort studies have suggested that SARS-CoV-2 infection promotes abnormalities in blood coagulation that could lead to arterial thromboembolism (ATE) or venous thromboembolism (VTE).
Few studies have examined how COVID-19-related thromboembolism risk evolved over time across different countries.

What was the aim of the study?

Regulatory agencies from Canada, Europe, and the US established a collaboration to evaluate the risk of ATE and VTE in the 90 days after diagnosis of COVID-19 in ambulatory and hospital settings in the periods before and during vaccine availability.

How was the study conducted?

A retrospective cohort study was conducted using routinely collected healthcare data from 7 countries: Canada, England, Germany, Italy, Netherlands, Spain, and the US.
The study cohorts comprised patients aged 18 years or older initially diagnosed with COVID-19 in the ambulatory setting between April 2020 and December 2021. A secondary analysis was undertaken in patients diagnosed in a hospital setting in Canada, Spain, and the US.
Patients were followed for 90 days after COVID-19 diagnosis to evaluate the risk of ATE (myocardial infarction or ischemic stroke) or VTE (acute deep venous thrombosis or pulmonary embolism).
Country-level estimates of absolute risk of ATE and VTE were measured before (through November 2020) and during COVID-19 vaccine availability (after December 2020).

What did the study find?

In the period before COVID-19 vaccine availability, about 1 million patients were diagnosed with COVID-19 in the ambulatory setting. The risk of ATE in the 90 days post-infection ranged from 0.11% (Canada) to 1.01% (US), and risk of VTE from 0.23% (Canada) to 0.84% (England).
About 3.5 million patients were diagnosed with COVID-19 during the period of vaccine availability. The risk of ATE in the 90 days post-infection ranged from 0.06% (England) to 1.04% (US), and the risk of VTE ranged from 0.25% (England) to 1.02% (US).
Variation in the risk of ATE and VTE across countries also was observed among patients diagnosed with COVID-19 in the hospital setting.
Differences in healthcare systems, data sources, prevalence of underlying comorbid conditions in the study cohorts, and approaches to COVID-19 and ATE and VTE case definition may have contributed to the variation in thromboembolism risk estimates observed between countries.

Link to publication: Lo Re et al, 2024.