“Initial data suggest that antigenic tests detect the omicron variant, but may have reduced sensitivity,” the FDA reported. This means that some cases may not be detected and have a higher risk of false negativity than previous coronavirus variants. He examines the effectiveness of the tests together with the National Institutes of Health.
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So far, the FDA has not mentioned how less sensitive it is, working to obtain further details. It was also not stated which tests from which manufacturers the findings concerned. Abbott said it had not yet detected a change in sensitivity in its BinaxNow test.
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“Studies are underway to show the reason for the apparent decline in sensitivity. As soon as it is known, anyone who has developed them can modify them with the support of the FDA, “the FDA told CNN.
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People who have passed a negative antigen test but still suspect that they have become infected should, according to the FDA, go for a more reliable PCR test that responds directly to the genetic material of the virus. PCR tests are more accurate, but take longer to evaluate.
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Anthony Fauci, director of the National Institute for Allergies and Communicable Diseases, which is fighting the pandemic in the country, called on people to continue testing with antigen tests: “These tests still make sense. Don’t let anyone think that these tests are no longer good. “They are less sensitive now, but they have never been 100% sensitive,” he told CNN. “They should continue to be used.”
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Rochelle Walen, director of the US Centers for Control and Prevention, emphasized that it was antigen tests that “keep children in school.”
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“If you use them regularly, you can accept a little less efficiency,” said Walenska. This is exactly the way in which they should be used in schools and companies in the Czech Republic from the beginning of the new year.
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Australian speed test warning
They have studied ten antigenic rapid tests in the Australian state of Victoria. It turned out that in the case of delta and omicron variants they are not able to detect less severe infections in vitro, in the delta it was from 6.50 log10 units per ml (Ct 25.4), in omicron it is 6.39 (Ct 28.8) and were unable to detect them at Ct 28. The effectiveness of four Chinese tests, one German, three Korean, one Canadian and one Australian, was examined.
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The Ct value indicates how many times the amplification cycle must be repeated in the PCR assay before a detectable amount of virus gene sequence appears. It is used in the detection of the virus and as a criterion for possible sequencing of the sample, ie finding out which variant it is. According to the Czech Ministry of Health, a patient with a Ct of 35 or more can be assessed as probably non-infectious under certain conditions.
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However, Australian experts also emphasize the importance of antigenic tests as a rapid means of detecting people with a large viral load, ie those who can spread the disease the most.
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