How accurate is your rapid test now? Experts intervene as Omicron fuels the 6th wave


Medical experts say Canadians should keep a supply of rapid antigen tests on hand as we head into a summer with almost no public health restrictions in much of the country. But experts add that a negative result does not necessarily mean someone is in the clear.

Canada is already experiencing a sixth wave of COVID-19 in the weeks since mask mandates and other measures were lifted across the country.

But while cases are on the rise, the public availability of PCR tests has not increased after being overwhelmed during the wave driven by Omicron that sent case numbers skyrocketing in January and February.

“I think most Canadians will have to be cautious about using the rapid test at home,” said Dr. Prabhat Jha, global epidemiologist at St. Michael’s Hospital in Toronto.

When should I use a rapid test?

Jha recommends people use a rapid antigen test if they start showing symptoms of COVID-19 or if they were at high risk to an unvaccinated or symptomatic person with COVID-19.

Even then, he says, not every situation would require taking a test.

A person examines a COVID-19 rapid test kit after queuing for free kits in Ottawa on January 7, 2022. Free kits are still available across Canada, at different locations depending on the province or territory. (Patrick Doyle/Reuters)

Instead, Jha suggests considering, “Was the person I came in contact with vaccinated? Was the person actively symptomatic? Was it an indoor, enclosed space where I could have catch a good load of his virus if he hacked?”

A positive result can also help an infected person get a better idea of ​​the risk to family members and others around them, especially as mask mandates rise and other respiratory viruses begin to spread. circulate more, said Dr. Susy Hota, medical director of infection control. and monitoring at the University Health Network in Toronto.

Regardless of a positive or negative COVID test result, the two doctors say a person with a respiratory illness should isolate themselves from others until they feel better. This way they will also avoid transmitting colds and flu.

What does a negative result mean?

Medical experts continue to warn that a negative rapid test result doesn’t necessarily mean you don’t have COVID-19. New Swiss researchwhich has yet to be peer-reviewed, suggests that some rapid tests have “significantly lower sensitivity” to Omicron than to the Delta variant.

In the same way, research by Ontario’s COVID-19 Science Advisory Table earlier this year, rapid tests are less sensitive for Omicron than the Delta variant in nasal samples, especially in the first two days after infection.

Doctors now recommend self-isolating immediately after symptoms or exposure, then waiting a day or two before using a rapid test, to get the most accurate result possible from a rising viral load.

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Early data suggests that the Omicron XE variant may be around 10% more transmissible than the highly infectious Omicron BA.2 subvariant. Experts urge measured caution, saying vaccinations are a way for the public to protect themselves. 2:03

“At that time, the rapid tests are less likely to give you a false negative result,” says Jha.

But it can still happen, says Hota, who recommends getting another quick test 24 hours later, keeping in mind that a second negative test “doesn’t necessarily rule it out.”

However, she adds, a positive result should always be accepted as a “true positive”.

Should I use a quick test before an event?

As the spring and summer social calendars fill up, Jha and Hota said it’s important to remember that a negative rapid test result is never a guarantee – and that other measures of security, such as keeping events outdoors, are always important.

“A single rapid test tells you with low sensitivity what your status is at the time you take the test,” Hota said.

“If you have the virus, in theory it’s possible that you’re less contagious to others at that time. That could change again within two hours of you being there…but that’s just not not something you should hang up your hat on.”

Jha cites a recent DC gala, the Gridiron Dinner, as an example: more than 10% of the 630 guests at the maskless indoor event — including cabinet secretaries, members of Congress and White House advisers — have since tested positive.

A person receives a rapid antigen test at Dalhousie University in Halifax on November 24, 2020. Self-administered rapid tests are now available free of charge at various locations across the country. (Robert Short/CBC)

However, says Jha, rapid tests can be helpful in identifying when you’ve recovered enough to return to work and resume socializing, “usually five days after the first positive test or the onset of symptoms.”

“If it’s turned negative by then, you’re pretty much free to go meet other people.”

What is the best technique for passing a test?

The technique you use to administer a rapid test to yourself or someone else is also very important. And experts say a quick swipe around each nostril is no longer enough, despite what the instructions in the box might say.

For a more accurate result, Hota recommends dabbing the lower inside of both cheeks, then the throat, tonsils, or back of the tongue — “depending on what you can tolerate” — then dabbing both nostrils. The swab should go about 2 centimeters into each nostril, for multiple circles, she said.

How many test kits should I keep at home?

Jha suggests making sure you have at least two tests per household member. “If you’re a typical family of four, you should have maybe 10 on hand.”

But how easy or difficult it is to get your hands on a free quick test depends on where you live in Canada, with provinces and territories distributing them through different channels.

Amid the fifth wave of COVID-19 over the winter, Canadians lined up for free rapid tests, including these people at a testing site in Markham, Ont., on January 12. (Paul Smith/CBC)

In British Columbia, for example, rapid tests are available for free at pharmacies, but those stores say they have trouble convincing people to take them.

Raj Rakholiya, director of Wilson Pharmacy in Port Coquitlam, B.C., says adoption is increasing as cases rise, but it’s still falling short of expectations: He currently has a stockpile of around 550 test kits.

“Most people say they’ve already had their three shots, now they’re going to save for their boosters, so they don’t need them. Some people say they’ve already had COVID, so they’re less likely to catch the new virus, so they don’t catch [tests].”

Infectious disease specialists say this is the wrong strategy: Thousands of Canadians have caught COVID-19 more than once, and reinfections are becoming more common, as the BA subvariant .2 of Omicron, more transmissible, is spreading in Canada.

“Although the risks are low, you can still get re-infected even if you’ve had COVID before,” Jha said.

“I think having rapid at-home testing is a sensible strategy that’s seen as sort of the new normal.”

People line up to get free rapid antigen test kits provided by the Ontario government at Queen’s University on January 11. (Lars Hagberg/The Canadian Press)

Where to find a free rapid test in your province or territory:

British Columbia: Available in pharmacies

AB: Available in packs of five at select Alberta Health Services pharmacies and clinics

Saskatchewan: Available at libraries, some grocery and gas stations, some municipal offices and other locations across the province

Manitoba: Available at provincial testing centres, pharmacies and grocery stores across the province and at libraries in Winnipeg

Ontario: Available in some grocery stores, pharmacies and community organizations

Quebec: Available in most pharmacies and in schools and nurseries (for registered families)

New Brunswick: Available for symptomatic people via the provincial government’s online portal (online registration required)

Prince Edward Island: Available at provincial ports of entry, Access PEI locations, schools and daycare (for registered families) and select community organizations

New Scotland: Available at MLA offices, Access Nova Scotia branches, public libraries, family resource centers, some food banks and pop-up sites

Newfoundland and Labrador: limited distribution in schools, health care centers, congregate residences and other selected establishments

Yukon: Available in select stores in Whitehorse and community administration buildings elsewhere in the territory

Northwest Territories: Available at City Hall and Field House in Yellowknife and grocery stores elsewhere in the territory

Nunavut: Available at Northern and Northmart stores