Scientists may soon be able to use a blood test to determine who is more prone to develop what is being called long COVID after they contract the novel coronavirus.

The blood sample would be used to detect important disease fighting antibodies, according to a study, Immunoglobulin Signature, which was published in the journal Nature Communication last month. It found that those who developed long COVID had low levels of some antibodies after contracting the coronavirus.

Onur Boyman, co-author of the study and a researcher in the department of immunology at University Hospital Zurich, said scientists "want to be able to recognize and identify as early as possible who is at risk of developing long COVID".

Varied symptoms

William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee, told China Daily that long COVID "can take a variety of forms - feeling fatigued is one of them, or not very strong, easy tiredness, a desire to nap and sleep longer …People feel as though they are not as limber as they were before".

"Some people even with very serious disease seem to recover completely. Other people with mild infections or perhaps even no symptoms seem to develop problems that can extend for quite a few weeks. And we don't know for how long yet."

The study by Boyman and his co-authors found that "about one-third of (all) individuals report one or more COVID-19-related symptoms that last for more than four weeks after the onset of the first COVID-19-related symptom, a condition termed post-acute COVID-19 syndrome or long COVID-19. Community prevalence of this has been estimated in most studies to lie between 10 percent and 60 percent".

Boyman and his co-authors conducted the research at the beginning of the pandemic in 2020. They looked at 500 patients, some of whom suffered long COVID and some of whom did not, and followed their prognosis from infection to six months later and then a year on.

The patients who took part became infected with coronavirus between April 2020 and August 2021.

The study did not cover the Delta or Omicron variants, detected later.

There were several key differences in the health of the patients who took part in the study. Most who suffered with long COVID had decreases in two immunoglobulins, IgM and IgG3. These two antibodies are produced by the immune system to battle infection. The levels of immunoglobulins in those with healthy immune systems rise when faced with infection.

Another influencing factor in who developed long COVID was health history and age. Those with asthma or other ailments in middle age were prime candidates for long COVID.