Rapid tests less sensitive to Omicron variant, but Ontario science table says new swab method can help
Ontario’s COVID-19 Science Advisory Table is urging people to change the way they use rapid antigen tests after determining the regular nasal swabs are less sensitive to the Omicron variant.
In a new brief released Thursday, the science table warned that a single negative rapid test “cannot reliably rule out infection” and shouldn’t be used as a “green light for abandoning or reducing precautions.”
A regular nasal sample, especially those taken in the first one or two days after infection, are less sensitive to the Omicron variant compared to the Delta strain, officials said.
“What we see based on early results, but very consistently, is that if you just use a swab of your nose, that especially early on during the first perhaps 48 to 72 hours after infection, the sensitivity of the test is relatively low. You won't detect Omicron infection that easily,” Dr. Peter Juni, scientific director of the advisory table, told CTV News Toronto in an interview.
“One of the reasons might be that the distribution of the virus is different than what we saw for previous variants.”
However, the science table says the tests can be more accurate if both cheeks are swabbed, in addition to the back of the tongue or throat, prior to going up the nose.
According to the brief, a nasal sample alone was about 68 per cent effective in detecting Omicron while a combined nasal and throat sample was about 82 per cent.
An instructional video released by the science table on Feb. 7 says that rapid test users should swab the inside of their cheeks, between the cheek and gums while rotating the swab for five seconds.
The video then instructs the user to swab the arch at the back of the mouth for another five seconds “in a circular fashion.”
A gag reflex is normal, officials said, but the process should not be painful.
Finally, users should insert the swab about two centimetres into the nose and gently wipe around the inside of the nostril about three to four times. Then, do the same in the other nostril.
“Stop advancing the swab when slight resistance is felt, even if it is less than two centimetres. No force is needed,” the video says.
The same swab should be used for the cheek, throat and nose.
Juni added that rapid test users should remember to start with the mouth, “otherwise it’s just a bit disgusting.”
If someone does the swab properly and still gets a negative test, the science table warns that it doesn’t necessarily mean the person is clear of infection.
“You still should not rely on a single negative test,” Juni said. “You should repeat tests and have two tests, perhaps 48 hours or more apart.”
A positive result using a rapid test can be considered accurate.
The province is providing free rapid antigen tests to Ontario residents at select grocery stores and pharmacies starting this week.
About 5.5 million tests will be distributed to just over 2,400 sites each week.
Witih files from CTV News Toronto's Colin D'Mello
CTVNews.ca Top Stories
![](https://www.ctvnews.ca/polopoly_fs/1.6978649.1722015109!/httpImage/image.jpg_gen/derivatives/landscape_800/image.jpg)
Missing 3-year-old boy found dead in creek in Mississauga, Ont.: police
A three-year-old boy has been found dead a day after he went missing in a park in Mississauga, Ont., Peel police say.
Celine Dion delivers stirring comeback performance at Paris Olympics opening ceremony
Against the rainy Paris night sky, Celine Dion staged the comeback of her career with a powerful performance from the Eiffel Tower to open the Olympic Games.
Jasper wildfire: 'Several weeks' before residents can return, premier says
Premier Danielle Smith said Friday afternoon in Hinton while weather conditions are cooler, the Jasper fire is still considered out of control and that Jasper residents can expect to be away from their homes 'for several weeks.'
Irish museum pulls Sinead O'Connor waxwork after just one day due to backlash
An Irish museum will withdraw a waxwork of singer-songwriter Sinéad O'Connor just one day after installing it, following a backlash from her family and the public, it told CNN in a statement on Friday.
Winnipeg senior's account overdrawn for $146,000 water bill
A Winnipeg senior is getting soaked with a six-figure water bill.
FBI says Trump was indeed struck by bullet during assassination attempt
Nearly two weeks after Donald Trump’s near assassination, the FBI confirmed Friday that it was indeed a bullet that struck the former president’s ear, moving to clear up conflicting accounts about what caused the former U.S. president’s injuries after a gunman opened fire at a Pennsylvania rally.
Driver charged after flashing high beams at approaching police
Orillia OPP arrested and charged a driver with impaired driving after flashing their high beams.
Turpel-Lafond won't sue CBC over Cree heritage report that took 'heavy toll': lawyer
The lawyer for a former judge whose claims to be Cree were questioned in a CBC investigation says his client is not considering legal action against the broadcaster after the Law Society of British Columbia this week backed her claims of Indigenous heritage.
Major Canadian bank experiences direct deposit outage on payday
Scotiabank says it has fixed a technical issue that impacted direct deposits on Friday morning.