Feb 11, 2022
By Jane Brown
Members of Ontario’s COVID-19 Science Advisory Table are 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 warns 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.”
“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 Zoomer Radio’s Fight Back with Libby Znaimer in a conversation on Wednesday.
He and the other science table members say 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.
An instructional video released by the science table on February 7th 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.”
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.
If someone does the swab properly and still gets a negative test, Dr. Juni cautions that it doesn’t necessarily mean the person is clear of COVID-19 infection.
“You still should not rely on a single negative test,” Juni told Libby. “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.