A study from Washington University School of Medicine in St. Louis and St. Jude Children's Research Hospital in Memphis, Tennessee, suggests that only 4 percent of coronavirus patients had the sky high levels of immune molecules that signify a so called cytokine storm.
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The researchers analyzed immune cells and molecules in blood samples from 168 coronavirus patients, 26 influenza patients and 16 healthy people. The samples were drawn from influenza patients in 2019 or 2020, and from coronavirus patients and healthy controls this year.
They also collected information about how each patient fared - whether a patient ended up needing intensive care or mechanical ventilation - and whether he or she survived.
The numbers of inflammatory cells in the blood of coronavirus and influenza patients were about the same. Seven or 4 percent of the coronavirus patients showed signs of a cytokine storm, with extremely high levels of cytokines even when compared to other severely ill patients.
The majority of the coronavirus patients with acute respiratory failure not only did not have a cytokine storm, they had less inflammation than influenza patients who were equally ill.
A few clinical trials have shown that some severely ill coronavirus patients improve on steroid drugs such as dexamethasone that suppress inflammation. The key will be to find a way to identify the people at high risk for a cytokine storm when they first arrive at the hospital.
"The subjects in the cohort with the 'true' cytokine storm phenotype are such outliers immunologically compared to the others, it seems likely that there are significant differences in multiple immune pathways driving this phenotype," said co-senior author Paul Thomas. "If we can identify features of those pathways that can be assessed quickly in a clinical setting, it could be useful for patient stratification."
With cytokine storm largely ruled out, the cause of most cases of respiratory failure in coronavirus patients remains unknown.
The findings were published Friday in Science Advances. ■