Long COVID: Study finds risk factors in patients’ blood


By examining the blood of patients with COVID-19, Swiss researchers have identified an antibody “signature” that can be used to predict the risk of long-term complications like extreme fatigue and shortness of breath.

They also found other risk factors for so-called long COVID, including the severity and number of initial symptoms, and a history of asthma.

“Overall, we believe that our findings and the identification of an (antibody) signature will help in the early identification of patients who are at increased risk of developing long COVID, which in turn will facilitate research, understanding and ultimately targeted treatments for long COVID,” the author, Dr. Onur Boyman of University Hospital Zurich, told CTVNews.ca.

Also known as post-acute COVID-19 syndrome, or PACS for COVID short, long, occurs when symptoms such as extreme fatigue, shortness of breath, cardiovascular problems, or cognitive impairment persist for weeks or even days. months after an initial recovery period. Although COVID has long remained poorly understood, it can be debilitating and is thought to affect between 10% and a third of those infected.

In the study, which was published Tuesday in the scientific journal Nature Communications, researchers compared 40 healthy people with 175 patients with COVID-19 at four hospitals in Switzerland. Patients were assessed and had blood tests when they were initially infected, about six months later, and again after about a year. More than half reported symptoms lasting longer than a month.

The researchers were ultimately able to identify several key risk factors for long COVID, including the severity and number of initial symptoms, advanced age, and a history of asthma. How the patients’ immune system initially reacted to the virus was also important. By analyzing their blood, the researchers were able to see that relatively low levels of immunoglobulin M (IgM) and immunoglobulin G3 (IgG3) antibodies soon after infection correlated with an increased risk of long-lasting COVID.

“As immunologists, we frequently work with immunocompromised patients who have low levels of immunoglobulins,” said Boyman, who chairs the department of immunology at University Hospital Zurich. “Also interesting is that patients with chronic fatigue syndrome, a condition similar to long COVID, appear to have altered immunoglobulin levels.”

Together, these factors were used to create a model that accurately predicted long COVID in an additional group of 395 patients. While more work needs to be done to see how vaccination status and the emergence of the Omicron variant affect study results, there is hope that the results can be used to help create the first test to screen for long-term complications of COVID-19.

In the meantime, Boyman notes that hospitals could simply test patients’ antibody levels to identify those most at risk.

“These are inexpensive and easy to measure in most clinics,” Boyman explained. “A single immunoglobulin measurement is enough to assess a patient’s risk of developing long COVID.”

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