Sept. 25, 2023 -- People with long COVID have specific biomarkers in their blood, a study published Monday in Nature said.
The findings may be a step toward creating blood tests to positively identify people with long COVID so specialized treatments can be employed, researchers said.
“This is a decisive step forward in the development of valid and reliable blood testing protocols for long COVID,” said David Putrino, PhD., lead author and Professor of Rehabilitation and Human Performance and Director of the Abilities Research Center at Icahn Mount Sinai Health System.
Researchers from the Icahn School of Medicine at Mount Sinai and Yale School of Medicine looked at blood samples from about 270 people between January 2021 and June 2022. The people had never been infected with COVID, had fully recovered from an infection, or still showed symptoms at least four months after infection.
Using machine learning, the research teams were able to differentiate between people with and without long COVID with 96% accuracy based on distinctive features in the blood samples, according to a news release from Mount Sinai.
People with long COVID had abnormal T cell activity and low levels of the hormone cortisol. Cortisol helps people feel alert and awake, which would explain why people with long COVID often report fatigue, NBC News said in a report on the study.
"It was one of the findings that most definitively separated the folks with long Covid from the people without long Covid," Putrino told NBC News.
The study also found that long COVID appears to reactivate latent viruses including Epstein-Barr and mononucleosis, the study said.
The blood tests could allow doctors to come up with specialized treatments in people who report a wide variety of long COVID symptoms, Putrino said.
“There is no ‘silver bullet’ for treating long COVID, because it is an illness that infiltrates complex systems such as the immune and hormonal regulation,” he said.
The CDC says about one in five Americans who had COVID still have long COVID. Symptoms include fatigue, brain fog, dizziness, digestive problems, and loss of smell and taste.