Long Covid: doctors find ‘antibody signature’ for patients most at risk

Doctors have discovered an "antibody signature" that can help identify patients most at risk of developing long Covid, a condition where debilitating symptoms of the disease can persist for many months.

Researchers at University hospital Zurich analysed blood from Covid patients and found that low levels of certain antibodies were more common in those who developed long Covid than in patients who swiftly recovered.

When combined with the patient's age, details of their Covid symptoms and whether or not they had asthma, the antibody signature allowed doctors to predict whether people had a moderate, high or very high risk of developing long-term illness.

"Overall, we think that our findings and identification of an immunoglobulin 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 for long Covid," said Onur Boyman, a professor of immunology who led the research.

The team studied 175 people who tested positive for Covid and 40 healthy volunteers who acted as a control group. To see how their symptoms changed over time, doctors followed 134 of the Covid patients for up to a year after their initial infection.

Blood tests on the participants showed that those who developed long Covid - also known as post-acute Covid-19 syndrome (Pacs) - tended to have low levels of the antibodies IgM and IgG3. When Covid strikes, IgM ramps up rapidly, while IgG antibodies rise later and provide longer-term protection.

The scientists combined the antibody signature with the patient's age, whether they had asthma and details of their symptoms to produce a long Covid risk score. To confirm that the score was useful, they ran the test on a separate group of 395 Covid patients that had been followed up for six months.