Rapid antigen test kits have flocked to supermarkets, online stores and pharmacies around the world as countries rush to keep pace with the rapid rate of transmission of the Omicron variant, marking a shift to self-administered testing PCR tests, which have long been considered the gold standard for detecting the coronavirus.
But there is no definitive international guideline for the use of antigen testing for Covid-19, and a global patchwork of policies has emerged as each country assesses the benefits and risks of the alternative testing method.
Britain has been using rapid home antigen tests to fight outbreaks since 2020, even before Omicron, and making them available for free. France started letting supermarkets sell them at the end of last month. The Biden administration recently said it plans to make 500 million tests available for free and that Americans could request that the tests be sent home.
Singapore has allowed people to leave isolation if they obtain a negative result in the antigen test after 72 hours. Israel is asking people to swab their throats when using rapid antigen tests, not just their nostrils, to increase the chances of detecting the virus even if it goes against the manufacturer’s instructions.
“There are widely varying approaches to where, when and how antigen testing is used in different countries,” said Deborah Williamson, professor of public health at the University of Melbourne in Australia.
The lack of consistency in how antigen testing is deployed raises the question of how the world should monitor the severity of the pandemic, she said, as some countries identify each case and others give priority for severe cases.
Plus, while promising faster results, antigen tests are significantly less reliable at detecting infection than PCR tests, studies have shown.
The self-swab in a home antigen test kit, which is intended to reach the inside of the nostril, is less than 30% capable of detecting a positive coronavirus case compared to the nasopharyngeal swab used in a PCR test, which reaches the wall at the end of the nasal cavity, said Dr Kiho Hong, professor of laboratory medicine at Yonsei University in South Korea.
As a result, health experts at American Society of Infectious Diseases said PCR testing is the method of choice for diagnosing Covid-19 infection. But they added that antigen testing could help identify cases where PCR testing was not readily available.
A shortage of PCR tests in countries like the United States and Australia has also left some people waiting hours and days for the result. This prompted Australian authorities to order people without symptoms of Covid to request a PCR test only if they had received a positive antigen test result.
Demand for antigen testing has become so overwhelming in Australia that the government last week started banning price hikes on the tests and said it would limit the number people can buy. And the state of New South Wales has ordered residents to report their positive rapid antigen test results from January 19. Those who fail to comply will be fined AU $ 1,000 (approximately $ 720).
“Omicron was a game-changer,” said Prof Williamson, adding that it “really catalyzed the move to large-scale rapid antigen testing.”
There is a pitfall to this change, she added: Governments may lose their ability to keep up with new variants and the extent of the virus’s spread, as not passing the self-test will capture all. the results.
Also, Professor Williamson said, with the Omicron variant, it is no longer realistic in many countries to keep track of every case.
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