The amount of SARS-CoV-2 antigen measured in the blood of patients hospitalized with COVID-19 is associated with illness severity and other clinical outcomes, according to a new study published in the Annals of Internal Medicine. Following the ACTIV-3 trial of COVID-19 therapeutics in people hospitalized with COVID-19, researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, and their collaborators analyzed levels of SARS-COV-2 antigen in blood samples taken from study participants and assessed the association of those levels with disease progression. Higher levels of viral antigen in the blood, which could indicate ongoing SARS-CoV-2 replication, correlated with more severe disease. The authors suggest that SARS-CoV-2 antigen levels hold promise as a biomarker, or a measurable substance, to predict which patients hospitalized with COVID-19 have a higher risk of worse outcomes.
The ACTIV-3 trial enrolled people hospitalized with COVID-19 between August 2020 and November 2021. Participants contributed a baseline blood sample and were then randomized to receive either an experimental COVID-19 therapeutic or a placebo. All participants received the antiviral remdesivir unless contraindicated. In this follow-up analysis, the researchers examined 2540 participant baseline blood samples for SARS-CoV-2 antigen levels.
The researchers assessed the relationship between each participant’s SARS-CoV-2 blood antigen levels and their time to discharge from the hospital, as well as their pulmonary symptoms at Day 5 of the trial—whether they had stayed the same, worsened, or improved since enrollment. With all this information in hand, the researchers conducted statistical analyses to determine if plasma antigen levels were associated with the participants’ pulmonary function when they gave the blood sample—and whether they could predict how the participants would fare over time. In addition, the researchers examined the relationship between a number of participant and viral characteristics and antigen levels.
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