Should you swab your throat while taking a COVID-19 rapid test? Answers vary by jurisdiction

There's more than one way to use a COVID-19 rapid test – and experts in different jurisdictions disagree about which one provides the most accurate results.

For almost two months, Ontario's COVID-19 Science Advisory Table has recommended that people swab their cheeks and throat before their nostrils, based on studies that found Omicron less likely to be detected when swabbing the nostrils alone.

"Rapid antigen tests are less sensitive for the Omicron variant compared to the Delta variant in nasal samples, especially in the first 1-2 days after infection," the group of advisors wrote in a Feb. 10 brief. 

"However, rapid antigen tests can more reliably detect infectious cases of the Omicron variant in combined oral-nasal samples."

The Ontario government's website includes step-by-step instructions for swabbing one's mouth and nose, an approach that has also been embraced in other countries, including the U.K. and Israel.

But in British Columbia, which is playing catch-up with other provinces when it comes to rapid test distribution, officials still only recommend swabbing the nostrils. Guidance from the B.C. Centre for Disease Control neither encourages nor discourages sampling from the mouth first. 

So who is right? According to Dr. Brian Conway of the Vancouver Infectious Diseases Centre, the science is anything but settled.

"It's a bit controversial," Conway said of the contention that swabbing the cheeks and throat increases accuracy.

"The British agree with this, the Americans disagree with this, saying that it's potentially giving us false-positive results."

Back in January, the U.S. Food and Drug Administration cautioned against throat-swabbing, partly in response to an increasingly popular #swabyourthroat hashtag used by people who had tested positive using that method.

Multiple Ontario residents who spoke to CTV News said they received negative results swabbing their nostrils alone, but tested positive after using their government’s mouth-swabbing instructions. 

Conway pointed to U.S. research that found the pH level in one's throat – which is different from the pH level in their nose, and can be impacted by the food and drinks they consume – could also influence test results.

He recommended that people follow the guidance of their own health officials. For British Columbians, that currently means only swabbing the nostrils, which happens to line up with the test manufacturers' instructions, at least for the BRNX Rapid Response kits being given away across the country.

But the province's advice could change. The Ministry of Health told CTV News the BCCDC is currently "conducting a validation study which will guide our approach going forward."

In the end, Conway said individuals are free to review the available science and decide for themselves how they want to proceed. Given the ever-changing nature of the pandemic, the epidemiologist encouraged the public never to rely on a single study for answers.

"Unfortunately, that makes it more grey than black-and-white, but it probably is the process that is required to get us to, ultimately, the right answer,” he said.

Whichever swabbing method people use, Conway stressed that nostrils are an integral step that shouldn't be skipped. He also encouraged anyone who hasn't picked up a free testing kit yet to do so, as the B.C. government still has millions of tests waiting to be distributed.

"For sure, get the tests. For sure, swab your nose," Conway said. "For now, I think that's the best guidance I could give."