COVID-19 Antigen Tests Detect Omicron Variant But May Have Reduced Sensitivity

Early data from preliminary studies evaluating the performance of some COVID-19 antigen tests using patient samples containing live SARS-CoV-2 virus suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity.

The study was conducted by the US Food and Drug Administration (FDA; Silver Spring, MD, USA) in collaboration with the National Institutes of Health’s (NIH Bethesda, MA, USA) RADx program as part of its efforts to evaluate the potential impact of genetic variants on antigen tests. Using patient samples containing live virus represents the best way to evaluate true test performance in the short-term.

Prior to completing these live virus tests, RADx conducted initial laboratory tests using heat-inactivated samples for some of the currently available antigen tests, which were able to detect the Omicron variant, with similar performance when detecting other variants. Heat-inactivated samples are patient samples with Omicron variant that have been heat-treated so that the virus is no longer live. Heat-inactivated samples are the best available option when patient samples with live virus are not available.

However, the FDA has clarified that these laboratory data are not a replacement for clinical study evaluations using patient samples with live virus, which are ongoing. The FDA and RADx are continuing to further evaluate the performance of antigen tests using patient samples with live virus. The FDA continues to authorize the use of these tests as directed in the authorized labeling and has asked individuals to continue using them in accordance with the instructions included with the tests. Antigen tests are generally less sensitive and less likely to pick up very early infections compared to molecular tests. Hence, the FDA has stated that if a person tests negative with an antigen test but is suspected of having COVID-19, such as experiencing symptoms or have a high likelihood of infection due to exposure, follow-up molecular testing is important for determining a COVID-19 infection.

Related Links:
US FDA 
National Institutes of Health (NIH) 

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