Published: 01-12-2020 11:36 | Updated: 01-12-2020 12:16

Ongoing anticoagulant treatment does not seem to protect against severe COVID-19

röda blodkroppar
There are different types of anticoagulants that prevent blood clots. This study focused on DOAC (direct oral anticoagulant) pills. Image: Pixabay

DOAC (direct oral anticoagulant) pills are used in the treatment of atrial fibrillation by preventing blood clots. Even though blood clots are thought to contribute to complications from the new coronavirus infection, users of this class of drug do not seem to be protected against severe COVID-19, reports a large Swedish registry study from Karolinska Institutet published in The Journal of Internal Medicine.

Benjamin Flam
Benjamin Flam. Photo: private

Early during the ongoing pandemic, there were reports that many patients with severe COVID-19 had blood clots in their pulmonary arteries and other parts of the body.

“Our hypothesis was that blood clots per se could contribute to the severe functional deterioration of the lungs and other organs that is associated with COVID-19, so one would think that preventative treatment with anticoagulants would provide some protection,” says Benjamin Flam, doctoral student at the Department of Physiology and Pharmacology, Karolinska Institutet, and specialist doctor in anaesthesiology and intensive care at Karolinska University Hospital.

Registry based study

To find out if this was the case, the team from KI conducted a registry based study of patients on anticoagulant medication for reasons other than COVID-19. The study included over 100,000 Swedes between the ages of 45 and 84 with atrial fibrillation being treated with DOACs. The control groups included over 350,000 individuals with cardiovascular disease who were not on such medication.

The researchers then examined the rates of hospitalisation, intensive care and fatality due to COVID-19 between 1 February and 31 May 2020, adjusting for such factors as age, sex, place of residence and other diseases and medication.

No difference between the groups

The results of the observational study show that DOAC use did not reduce the rate of hospitalisation, intensive care or fatality due to COVID-19.

“Our findings suggest that early DOAC treatment doesn’t protect against severe COVID-19, but these should be treated with caution since there might remain differences between the groups that are difficult to measure,” says Benjamin Flam. “Also, our study says nothing about whether other types of anticoagulants could be effective, but a good many clinical studies are being done around the world.”

The research was financed by grants from Region Stockholm (ALF funding), the Strategic Research Area in Epidemiology at Karolinska Institutet and the Swedish Research Council. Co-author Jonas F Ludvigsson is leading a study funded by the company Janssen on behalf of the Swedish IBD quality registry (SWIBREG). 


”Direct oral anticoagulant use and risk of severe COVID-19”. Benjamin Flam, Viktor Wintzell, Jonas F Ludvigsson, Johan Mårtensson och Björn Pasternak. Journal of Internal Medicine, online 1 December 2020, doi: 10.1111/joim.13205.