Research published on April 7 found that nCoV infection increases the risk of serious blood clot formation three to six months after infection.
Swedish, British and Finnish scientists compared more than a million people who had been infected with nCoV with 4 million patients without the disease between February 2020 and May 2021.
They found that three months after testing positive, patients had a 4% increased risk of developing deep vein thrombosis, a type of blood clot in the thigh or lower leg. Patients also had a 17% chance of developing a pulmonary embolism, a blood clot in a blood vessel and migration to the pulmonary artery within 6 months of testing positive.
The team said the results add to evidence of Covid-19 and severe blood clotting, and provide more information on how long the sequelae of the disease may last.
“These findings have major implications, reinforcing the importance of vaccination against Covid-19,” the study’s authors said.
They also said that Covid-19 patients, especially those at high risk, should take anticoagulants.
During the study period, scientists recorded 401 deep vein thrombosis in the Covid-19 positive group, more than 267 cases in the negative group. The number of cases of pulmonary embolism in people infected with the virus is more than 1,700, while those without infection are 171.
Covid-19 patients are at higher risk of blood clots if they have underlying medical conditions, have severe symptoms, or become infected during the first outbreak in 2020.
Besides the risk of blood clots, the study also showed bleeding after two months in people infected with Covid-19.
They note that the work has some limitations. This is an observational study, rather than a randomized controlled trial. Experts also recognize that blood clotting in Covid-19 patients may be underdiagnosed, with no information on vaccination status available.
The biological mechanism involved in venous thrombosis and pulmonary embolism is unknown. Scientists have different theories.
Research from the Michigan Institutes of Medicine and the US National Lung Institute shows that the overproduction of antibodies from a Covid-19 infection causes blood cells to lose their anticoagulant properties. Other research from Yale University School of Medicine indicates that specific proteins are produced by endothelial cells – cells that line blood vessels – due to inflammation from viruses and leading to blood clots.
Thuc Linh (According to AFP)
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