With the fall flu season looming and new COVID-19 variants continuing to circulate across the country, attention is once again turning to rapid antigen testing.
However, this flu season is different than last, as the federal government has stopped its deliveries of rapid tests to provinces and territories, meaning Canadians may have to look a little harder to find them, or even pay for them. out of pocket, experts say.
Faced with the decrease in supply, the increasing number of expired tests and the emergence of new variants of COVID-19 in the country, the question arises: are rapid tests still effective?
“I still see value in testing because SARS-CoV-2, the virus that causes COVID, spreads longer than we tend to see with some other respiratory infections,” explained Dr. Gerald Evans , an infectious disease specialist at Queen’s University in Kingston, Ontario.
“This could inform you of the likelihood that you will need to miss work a little longer than expected.”
In March 2023, the federal government stopped new deliveries of rapid antigen tests to provinces and territories. Health Canada said the decision to end shipments was made in collaboration with the provinces and territories because the regions had sufficient supply.
At the time, Ottawa said that since the start of the pandemic, it had ordered more than 811 million rapid tests at a cost of about $5 billion. About 680 million of these amounts went to the provinces and territories.
Health Canada said that as of March there were 90 million rapid tests in the federal inventory, but that 6.5 million of them will expire this year. The remainder expires within two years.
Can expired rapid tests still be used?
Nazeem Muhajarine, a professor of epidemiology at the University of Saskatchewan, estimates that rapid test kits are likely still good 15 to 20 months past the expiration date — and even said he recently used a test that died in May on a member of his family.
“I think the expiration dates are listed very conservatively, as they should be,” he said. “That being said, you can get a new test kit and use it, so you know you’re using it before that expiration date.
Rather than focusing solely on the exact expiration date, Muhajarine argued that it is crucial to prioritize correctly carrying out instructions, which includes careful swabbing of the nose and throat.
This also involves storing test kits in a place out of direct sunlight and not placing them in the refrigerator, he added.
In an email to PKBNEWS on Thursday, a Health Canada spokesperson said the expiration dates and expected shelf life of rapid antigen tests are brand specific.
“Companies conduct extensive research to bring together the data to demonstrate that their tests…work over a period of time and also under the changing conditions and temperatures in Canada,” the spokesperson said.
“The shelf life of a test kit is established based on the component of the test kit with the shortest shelf life. As part of their application for authorization of a test device, companies establish an estimated shelf life and expiration date based on the data they have collected to demonstrate that the test will continue to work as intended and over what period of time.
The permitted shelf life (not including extensions) can be found in the Test Information section of Health Canada’s list of authorized testing devices.
BTNX, the manufacturer of the rapid response COVID-19 antigen testing device, said that unless Health Canada grants a shelf life extension to its product, it cannot be used beyond of the expiration date.
“They already have a shelf life of 24 months from the date of manufacture,” a spokesperson told PKBNEWS in an email Thursday.
Evans added that some rapid test manufacturers have conducted their own studies to a*sess the accuracy of their tests even after the expiration date.
He said the problem with rapid tests is that they can become less sensitive over time and their accuracy becomes questionable.
“I want to emphasize that if you have a COVID test and you use it – whether it’s expired or not – and it comes back positive, it’s pretty reliable. When a positive test is positive, it’s a true positive,” he explained.
“But be careful with negative tests because they might be a little unreliable. When they are less sensitive, this means that they can be negative even though you actually have the disease.
An effective strategy for improving test accuracy is to perform tests repeatedly over three consecutive days. This approach increases the likelihood of detecting a positive result, Evans said.
Will the tests work against the new variants?
Early data from preliminary studies suggests that antigen tests detect the Omicron variant but may have reduced sensitivity, according to the U.S. Food and Drug Administration (FDA).
“Everything that exists now is essentially a subvariant of Omicron,” Evans said, so the rapid tests might be less sensitive to lineages circulating in the country, such as EG.5 and BA.2.86.
In light of this, Evans reiterated that if you feel unwell and receive a negative test result, you should complete two additional tests.
Muhajarine said the tests should work against the new variants.
This is because antigen-based test kits are specifically designed to detect the presence of a nucleoprotein, a key marker a*sociated with the virus (which generally does not mutate). However, when a virus mutates, it usually happens in the Spike protein, he said.
“And so the formulations in this test still work even though the spike proteins have changed,” Muhajarine added.
Where can we find rapid antigen tests in Canada?
Because Ottawa has stopped sending rapid antigen tests to provinces and territories, Evans said it may be difficult to find them in the fall.
Drugstores and grocery stores are a good place to start looking for one, he said.
In the past, provinces provided these tests for free to these locations, but now that supply is limited, he said stores may start charging for them.
If people end up having to buy them, Evans suspects most won’t want to spend out of pocket.
“And at the very least, (provincial) public health officials might be able to point you in the right direction to where you might be able to get a test,” Evans said.
— With files from Saba Aziz of PKBNEWS and the Canadian Press