Researchers predict risk of long COVID with patients' blood

Specimens to be tested for COVID-19 are seen at LifeLabs after being logged upon receipt at the company's lab, in Surrey, B.C., on Thursday, March 26, 2020. THE CANADIAN PRESS/Darryl Dyck

By looking at COVID-19 patients’ blood, researchers in Switzerland 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 what’s known as long COVID, including the severity and number of initial symptoms, and a previous history of asthma.

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

Also known as post-acute COVID-19 syndrome, or PACS for short, long COVID occurs when symptoms such as extreme fatigue, shortness of breath, cardiovascular issues or cognitive impairment linger for weeks or even months after an initial recovery period. While long COVID remains poorly understood, it can be debilitating and is believed to affect anywhere from 10 per cent to one third of those who have been infected.

In the study, which was published Tuesday in the scientific journal Nature Communications, researchers compared 40 healthy people with 175 COVID-19 patients at four hospitals in Switzerland. The patients were assessed and given blood tests during their initial infection, about six months later, and again after approximately one 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, older age and a previous history of asthma. Also of significance was how patients’ immune systems initially reacted to the virus. By analyzing their blood, researchers were able to see that comparatively low levels of antibodies immunoglobulin M (IgM) and immunoglobulin G3 (IgG3) soon after infection correlated to an increased risk of long COVID.

“As immunologists, we frequently work with immunodeficient patients that have low levels of immunoglobulins,” said Boyman, who chairs the University Hospital Zurich​'s department of immunology. “Interestingly also 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 impacts the study’s results, there is hope the findings can be used to help create the first test to screen for perplexing long-term COVID-19 complications.

In the meantime, Boyman notes 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 sufficient to assess a patient's risk of developing long COVID.”

Our first paper on long COVID is out! @NatComm

We identified an immunoglobulin signature able to predict the risk to develop post-acute COVID-19 syndrome (PACS).
How does this work and who can profit? A thread.
1/https://t.co/BeqqcIVzH3

— Carlo Cervia (@carlo_cervia) January 25, 2022