Persistent research into understanding the condition known as "long COVID" is finally clearing up clinical confusion and is also paving the way for the development of tests and treatments.
The study, published Jan. 18 in Science, tracked 113 patients diagnosed with COVID-19 for up to one full year after infection and found that 35% of them — 40 patients — had developed long COVID by the six-month follow-up. They repeatedly took blood samples from the 113 patients and 39 controls and found that among the 40 patients who developed long COVID, they "showed elevated tissue injury markers in blood," and a unique protein signature, which indicates an active complement system — the part of the immune system that cleans up damaged cells and works to heal the body after an injury or an infection.
If the complement system remains active in this infection-fighting, injury-healing state for longer than it normally should, however, it can begin to damage healthy tissue and cells, study author Onur Boyman, MD, a professor of immunology at the University of Zurich in Switzerland, told NBC.
Sometimes, the cells damaged cells are endothelial cells, which helps explain some long COVID patient's inability to return to normal exercise, he added.
During exercise the heart pumps blood ruffling the endothelial cells, which healthy cells can handle,"but the inflamed endothelial cells in long COVID patients cannot," Dr. Boyman told NBC. This is why getting a full breath during exercise for long COVID patients can feel almost unattainable to some.
Understanding unique biomarkers of long COVID like increased hemolysis, tissue injury, platelet activation, and monocyte–platelet aggregates, as well as what is behind its effects on the body paves a way forward for the development of tests and future treatments, according to the researchers. A possible way to detect the condition, is part of what makes this study so unique. The research also highlights the "the molecular mechanism of how" tissue damage and blood clotting associated with long COVID occurs, Akiko Iwasaki, PhD, a professor of immunobiology and molecular, cellular, and developmental biology at Yale University told the outlet.
"Understanding the mechanisms of long Covid is how we’re going to figure out treatments," Monica Verduzco-Gutierrez, MD, chair of rehabilitation medicine at the University of Texas Health Science Center at San Antonio and leader of its long Covid clinic told NBC. Dr. Verduzco-Gutierrez was not involved in the study, but applauded it upon review.
While the study is promising, before tests or treatments can be developed, the research must be replicated first, according to the study authors.