Wednesday,  February 24, 2021  5:43 pm

Why does Canada accept PCR (instead of antigen) tests? Health Canada explains


Why does Canada accept PCR (instead of antigen) tests? Health Canada explains
(Unsplash/United Nations COVID-19 Response)
Michael Pihach

Michael Pihach is an award-winning journalist with a keen interest in digital storytelling. In addition to PAX, Michael has also written for CBC Life, Ryerson University Magazine, IN Magazine, and DailyXtra.ca. Michael joins PAX after years of working at popular Canadian television shows, such as Steven and Chris, The Goods and The Marilyn Denis Show.

Travel agents are the new lab rats.

At least that’s what the Canadian government would have you think based on its new pre-departure COVID-19 testing requirements for international travellers.

There’s a laundry list of previously-unspoken health words and scientific processes the travel industry has had to learn since the beginning of the COVID-19 pandemic.

The latest learning curve has been around COVID-19 testing and the different methods that are available.

Since Jan. 7, all air passengers entering Canada have been required to provide proof of a negative COVID-19 test before arriving in the country.

Under the new policy, travellers must receive a negative COVID-19 test within 72 hours of their departure time. Those who fail to show proof of their results will be denied boarding. 

There are different kinds of COVID-19 tests, and for travel agents, understanding the various methods, and explaining to clients how they work, has become part of the job.

READ MORE: What happens if I can't get a test in destination? Transport Canada answers your questions

PCR testing is considered the gold standard in COVID-19 detection.

The test typically involves using a swab inserted into a person’s nose or throat and the tests are processed in a lab.

The turnaround time can range anywhere between 24 hours to three or four days. 

LAMP (loop-mediated isothermal amplification) is a relatively new DNA amplification technique that also uses a swab from throat and nose.

In contrast to PCR, which detects COVID-19 using various temperatures and cycles, LAMP testing is performed at a constant temperature and does not require a thermal cycler. These tests can also have faster processing times. 

PCR and LAMP molecular tests are the two leading methods currently accepted by the Government of Canada under its pre-departure testing order.

READ MORE: "Callous and impractical": IATA blasts Canada's new COVID-19 testing requirement

Then there’s antigen tests.

You may have heard about these recently as this is the method the United States will accept from international arrivals (as part of a mandatory requirement) starting Tuesday (Jan. 26).

A COVID-19 rapid test. (Unsplash)

Commonly referred to as rapid tests, antigen tests detect protein fragments specific to COVID-19 and results can be processed within 15 minutes.

READ MORE: All air travellers arriving in U.S. must provide negative COVID-19 test, says CDC

On the heels of the new U.S. travel requirements, hotels and resorts in the Caribbean have quickly begun to unveil on-site testing options for visitors.

As the U.S. is driving most tourism in tropical destinations these days, establishing a plan for antigen tests may be viewed as a priority by some hotels and destinations over PCR testing. 

(Although, some brands have committed to PCR services. Always check in advance, as a rule of thumb). 

An antigen test will be useless to you if you’re a traveller returning to Canada, so it’s important to know exactly which type of test you (or your client) is getting.

But why does Canada, when screening international travellers, only accept some types of tests and not others?

PAX connected with Tammy Jarbeau, senior media relations advisor at Health Canada and the Public Health Agency of Canada, to learn more.


PAX: Why are only PCR and LAMP tests accepted in Canada?

Tammy Jarbeau (TJ): COVID-19 molecular tests, also known as “polymerase chain reaction” (PCR) and reverse transcription loop-mediated isothermal amplification (RT-LAMP) tests are currently the most accurate tests for detecting COVID-19. PCR and RT-LAMP tests are performed on a nasopharyngeal sample (NP) or alternate respiratory sample collected by a health care professional.

Both tests have the ability to detect traces of the virus in asymptomatic individuals.

PAX: Are these tests "better" than antigen tests?

TJ: While both molecular and antigen tests can be used to diagnose COVID-19, their respective characteristics make them suited for different scenarios. While they can be easier and quicker to use, antigen tests are generally less sensitive than PCR and RT-LAMP tests for COVID-19 detection, so they may be less accurate.

In the context of pre-travel testing, the technologies that afford higher sensitivity are better suited since they are better able to detect individuals that might be in an early stage of infection.

PAX: Will Canada ever accept antigen tests from international arrivals, like in the U.S.? 

TJ: The Government of Canada’s top priority is the health and safety of Canadians. The measures taken under the Quarantine Act, including mandatory pre-border testing and quarantine for incoming travellers, have been put in place to reduce the risk of travel-related cases of COVID-19. These measures have been essential to slowing the spread of the virus, including new variants, within Canada’s borders. At this time, only a molecular test, such as PCR or LAMP, is acceptable to meet Canada’s pre-border testing requirement.

In making its decisions on extensions or amendments to the Emergency Orders, the Government of Canada continues to review the available scientific evidence and closely monitor the epidemiological situation, both domestically and internationally. As knowledge of COVID-19 and its variants evolve, alternative border and testing approaches, such as those implemented by other jurisdictions, will be considered.

PAX: If a passenger is travelling back to Canada, via the United States, do they need two types of tests? One PCR (for Canada) and one viral (for U.S.)? Or is one PCR test enough for both countries? 

TJ: The U.S. will accept a viral detection test for current infection (i.e., a nucleic acid amplification test or a viral antigen test) approved or authorized by the relevant national authority for the detection of SARS-CoV-2. Canada is accepting PCR and LAMP, both of which are nucleic acid amplification tests for viral detection. Therefore, tests required by Canada will be accepted by the U.S. but note that an antigen test is accepted by the U.S. but not by Canada.


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