Health officials in the US are warning that at-home antigen COVID-19 tests may be less effective at detecting cases of the Omicron variant – the super infectious variant that’s currently swarming parts of the word – compared to other strains.
On December 28, the US Food and Drug Administration (FDA) released a statement saying: “Early data suggest that antigen tests do detect the omicron variant but may have reduced sensitivity.” In other words, if you are infected with the Omicron variant, some antigen tests may be more likely to provide a false negative result than if you had Delta.
Until this issue is resolved, the FDA says the two following brands of antigen tests are "expected to fail to detect" the Omicron variant, so people should take extra precautions: Meridian Bioscience, Inc. Revogene SARS-CoV-2 and Applied DNA Science Linea COVID-19 Assay Kit.
The FDA still advises people to use antigen tests just as before, although they should be aware of other factors. If you’ve had a negative result with an antigen test, but you are experiencing symptoms or have been exposed to a confirmed case of COVID-19, then you should get a follow-up molecular test, also known as a polymerase chain reaction (PCR) test, to be sure.
Sometimes referred to as rapid lateral flow tests, antigen tests work by detecting proteins known to be associated with SARS-CoV-2, which are present when someone is infectious. PCR tests work by detecting the virus’s genetic material, RNA. In comparison, PCR tests are very accurate and significantly more sensitive as they involve a step where the genetic material of the virus is amplified, making it easier to spot.
One tip that could help antigen tests detect a case of Omicron is ensuring to thoroughly swab the throat. Some of the newer tests advise people to only swab the nostril, but some health experts have argued for swabbing in the throat around the tonsils as well. In fact, a preprint paper (not yet peer-reviewed) found saliva swabs had a 100 percent accuracy rate for detecting Omicron compared to the less accurate nasal swab.
“Well, there it is. Today, with the “wrong” (i.e. cold) symptoms and after a string of negative LFTs, I finally took Twitter advice and swabbed my throat as well as my nose (no mean feat with that diddly stick). If you think you might have COVID, consider adding the throat sample,” tweeted Professor Jennifer L Rohn, a cell biologist at University College London.
“These instruct the user to perform nasal sampling only. Other kits are designed for dual tonsil/nasal sampling. My suggestion is to perform dual even for former,” added Professor Rohn.
Of course, all of this depends of whether you can actually get your hands on any tests. The US continues to lag in testing and many Americans struggled to get a COVID-19 test over the Christmas period.
“Seeing how tough it was for some folks to get a test this weekend shows that we have more work to do, and we’re doing it,” President Joe Biden said in a recent address.
President Biden noted that over-the-counter home tests were not available in the US when he took office back in January. Although a number have now been made available, he conceded that much more needs to be done.
“We went from no over-the-counter tests in January to 46 million in October, 100 million in November, and almost 200 million in December,” he said. “But it’s not enough. It’s clearly not enough. If I had — we had known, we would have gone harder, quicker if we could have.”