COVID-19 patients with particularly elevated levels of a protein called MYL9 in their blood post-infection were likely to suffer from severe symptoms, a research team led by Chiba University Hospital has found, suggesting that the protein could be used as a biomarker to predict the possibility of patients developing a serious case of the disease.

In a study published in late July in the U.S. journal Proceedings of the National Academy of Sciences, researchers analyzed blood samples collected from 130 COVID-19 patients who were treated at 11 hospitals in Japan. They found that the higher the levels of MYL9 in their blood were, the longer their hospitalization periods were.

MYL9 is a protein that exists in platelets — tiny blood cells that can form clots to stop bleeding. When blood vessels are damaged, platelets release MYL9 to achieve this clotting.