With the impending fall flu season and the continued circulation of new COVID-19 variants across the country, attention is once again turning to rapid antigen tests.
However, this flu season is different from the last, as the federal government stopped its shipments of rapid tests to the provinces and territories, meaning Canadians may have to look a little harder to find them, or even pay out of pocket, experts say.
Given the dwindling supply, increasing numbers of expired tests and the emergence of new COVID-19 variants in the country, the question arises: Are rapid tests still effective?
“I still see a value in the tests, because SARS-CoV-2, the virus that causes COVID sheds for a longer time than we tend to see with some the other respiratory infections,” explained Dr. Gerald Evans, infectious disease specialist at Queen’s University in Kingston, Ont.
“It would be able to inform you of the likelihood you might have to be off work for a little bit longer than you were expecting.”
In March 2023, the federal government ended new shipments of rapid antigen tests to provinces and territories. Health Canada said the decision to end shipments was made in collaboration with provinces and territories, as the regions had enough supply.
At the time, Ottawa said since the pandemic started it had ordered more than 811 million rapid tests with a price tag of about $5 billion. About 680 million of those went to provinces and territories.
Health Canada said that in March there were 90 million rapid tests in the federal inventory, but 6.5 million of those will expire this year. The rest expire within two years.
Can expired rapid tests still be used?
“I think the expiration dates are very conservatively labeled, as they should,” he said. “That being said, you can get a new test kit and use that, so you know that you are using it within that expiration date.”
Rather than fixating solely on the exact expiry date, Muhajarine argued it is crucial to prioritize the correct execution of instructions, which includes thorough swabbing of the nose and throat.
This also entails storing the testing kits in a spot away from direct sunlight and refraining from placing them in the refrigerator, he added.
In an email to Global News on Thursday, a spokesperson from Health Canada said the expiry dates and expected shelf life of rapid antigen tests are specific to the brand.
“Companies do extensive research to gather the data to demonstrate that their test… function over a period of time and also under the changing conditions and temperatures in Canada,” the spokesperson said.
“A shelf-life for a test kit is established based on the component within the test kit with the shortest shelf life. As a part of their application for authorization of a testing device, companies establish an estimated shelf life and expiry date based on the data they have collected to demonstrate the test will continue to perform as intended and over what period of time.”
The authorized shelf-life (not including extensions) can be found in the testing information section of Health Canada’s list of authorized testing devices.
BTNX, the manufacturer of the Rapid Response COVID-19 Antigen Test Device, said unless Health Canada has given a shelf-life extension to its product, it cannot be used past the expiry date.
“They already have a shelf-life of 24 months from date of manufacture,” a spokesperson told Global News in an email Thursday.
Evans added some rapid test manufacturers have conducted their own studies to assess the accuracy of their tests even after the expiry date has passed.
He said the problem with rapid tests is that they can become less sensitive over time and accuracy becomes questionable.
“I would underscore that if you have a COVID test and you use it — whether it’s expired or not — and it comes up positive, that’s pretty reliable. When a positive test is positive, it’s a true positive,” he explained.
“But be careful with the negative tests because they might be a bit unreliable. When they’re less sensitive, it means they can be negative when you actually have the disease.”
One effective strategy for improving the accuracy of the tests is to perform them repeatedly over the course of three consecutive days. This approach increases the likelihood of detecting a positive result, Evans said.
Will the tests work against new variants?
Early data from preliminary studies suggests that antigen tests detect the Omicron variant but may have reduced sensitivity, according to the United States Food and Drug Administration (FDA).
“Everything that’s out there now is basically an Omicron subvariant,” Evans said, so rapid tests may be less sensitive to the lineages circulating the country, such as EG.5 and BA.2.86.
In light of this, Evans reiterated, that if you are feeling unwell and receive a negative test result, you should perform two additional tests.
Muhajarine said the tests should work against the new variants.
This is because the antigen-based test kits are specifically designed to detect the presence of nucleoprotein a key marker associated with the virus (which usually does not mutate). However, when a virus mutates it usually happens in the spike protein, he said.
“And so the formulations of this in this test still work even though the spike proteins have changed,” Muhajarine added.
Where can you find rapid antigen tests in Canada?
Because Ottawa stopped sending shipments of rapid antigen tests to the provinces and territories, Evans said it may be difficult to find them in the fall.
Pharmacies and grocery stores are a good place to start looking if you are on the hunt for one, he said.
In the past, provinces have been providing these tests for free at these locations, but now that there is a limited supply, he said stores may start charging for them.
If people end up having to buy them, Evans suspects most won’t be keen on spending out of their pocket.
“And if nothing else, the (provincial) public health people might be able to point you in the right direction to where you might be able to pick up a test,” Evans said.
— With files from Global News’ Saba Aziz and the Canadian Press
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