Once a cornerstone of the pandemic response, COVID-19 testing undergoes a paradigm shift

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Over the past two years, mass COVID-19 testing became a pop-up government utility, as essential to a functioning Canada as public transit or snow-free streets. At peak testing rates, nearly 170,000 Canadians a day were lining up to get their nasal discharge swabbed, shipped to a lab and subjected to PCR, or polymerase chain reaction, analysis. The results had the power to upend family holiday plans and alter the government’s pandemic response.

Those days of collective dependence on PCR tests to surveil and subdue the pandemic may be over, as governments seek to guide the country away from pandemic vigilance and toward endemic acceptance. But some public-health experts are warning that the country needs a new testing strategy to avoid future outbreaks.

On Thursday, Saskatchewan became the latest province to place strict limits on PCR tests. As of next week, drive-thru and walk-in testing centres in the province will close and anyone wanting a test will have to call the government’s 8-1-1 health line to be screened. Only people at risk of severe outcomes and health care workers will get appointments.

The shift is part of the government’s “Living with COVID” plan, which emphasizes self-management.

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“COVID will now be monitored and managed similar to other seasonal viruses … like influenza, which will allow public health and health care capacity for preventing and treating severe cases,” said Saqib Shahab, Saskatchewan’s Chief Medical Health Officer, during a Feb. 3 briefing.

In the pandemic’s early days, the purpose of PCR was clear: root out positive cases and outbreaks, underpin contact-tracing efforts and provide reliable surveillance numbers.

But all that broke down during the Omicron wave.

The volume of testing demand overwhelmed labs, forcing most jurisdictions to restrict PCR testing to high-risk groups and health workers. Official case counts became wildly unreliable. The combination of long lab delays and Omicron’s shortened incubation time (three days, versus five for the original strain) meant contact tracers didn’t have enough time to seek out and break chains of transmission.

“I honestly don’t think we will go back to widespread surveillance through PCR testing,” said Brenda Wilson, public-health physician, researcher with Memorial University of Newfoundland and member of the federal screening and testing expert panel. “Testing has to change. I know that won’t go over well with people. But Omicron has thrown a wrench in the works.”

National daily testing has dropped from a peak of around 170,000 over the holidays to roughly 100,000 this week. Both figures are anemic compared with those in other countries. Our rolling seven-day average of tests is 238 per 100,000 people, according to Johns Hopkins University data. That compares with 390 in the United States, 1,836 in Britain and 2,617 in Portugal. Despite that low rate, provincial governments have shown little desire to catch up.

In B.C., Provincial Health Officer Bonnie Henry said PCR testing should focus on the medically vulnerable and health workers. “PCR in our publicly funded system needs to focus on people for whom it will make a difference in their care or for going back to work.”

In Manitoba, Chief Public Health Officer Brent Roussin has articulated a similar “test in order to treat” strategy and said that increasing PCR access wouldn’t make much difference for surveillance or contact-tracing purposes because of the increased transmissibility and shortened incubation period of Omicron.

On Thursday, Kieran Moore, Ontario’s Medical Officer of Health, widened PCR testing eligibility slightly to include the families of patient-facing health care workers, but said all future changes to PCR testing would be done slowly and judiciously.

All three officials advise low-risk symptomatic people to self-manage and self-isolate. For the most part, that strategy is sound, according to health experts.

“For the average person who is mildly ill and can self-isolate to recover, do they really need to be tested? For me, the answer is no,” said Tony Mazzulli, microbiologist-in-chief for Toronto’s Mount Sinai Hospital and University Health Network, where the lab performs tests for up to 24 hospitals and 15 assessments centres. “It’s not going to change their management. It’s no different than testing for the flu.”

For people who no longer qualify for PCR tests, rapid antigen tests will do the job. They’re less accurate than PCR, but what they lack in accuracy they make up for in speed, cost and ease of use. But availability varies from province to province.

The federal government has already shipped 185 million rapid tests to the provinces and territories, with millions more to come. Each jurisdiction has a slightly different distribution plan. Alberta, for instance, is making millions available on a first-come-first-served basis at pharmacies and health facilities across the province. B.C., meanwhile, is planning to send the 10 million rapid tests it has received from Ottawa to “areas of greatest need,” according to Health Minister Adrian Dix, including acute-care centres, long-term care homes, remote Indigenous communities and schools.

Reducing COVID-19 PCR testing comes with perils. Without robust surveillance, including testing a cross-section of patients and conducting genomic sequencing to look for new variants, the country becomes blind to incoming threats.

“Sudden outbreaks are very hard to call in terms of timing, but what you have to do, as maddening as it is, is remain on guard, even if it looks like money badly spent,” said David Naylor, who co-chairs the federal government’s COVID-19 immunity task force.

Dr. Naylor, who chaired the national review of public health following the 2003 SARS outbreak, says the country needs to maintain what’s called widespread multiplex testing, where a single test detects a range of viruses. Some multiplex tests being used in Ontario can test a sample for up to 21 different viruses.

“As this recedes, then you still want some way to pick up signals as people turn up with respiratory illnesses,” he said. “You need to know what’s going on. Part of that is being smart about test patterns.”

He also urges governments to maintain and even enhance the waste-water testing that became a valuable surveillance tool as case-count figures became unreliable.

In the last few months, a new reason has emerged to maintain robust PCR testing capacity: A handful of life-saving COVID-19 antivirals have recently become available, such as Pfizer’s Paxlovid, and many need to be administered early in the virus’s course.

“That person needs to know they have COVID to be treated with these drugs,” said Irfan Dhalla, a physician, vice-president with the Unity Health Toronto network of hospitals and co-chair of the federal COVID-19 Testing and Screening Expert Advisory Panel. “Those people need to get a test very soon after they get symptoms to be eligible for treatment.”

Dr. Dhalla says the aim of COVID-19 testing is undergoing a shift. “It’s less about preventing transmission,” he said “and more about providing really good care to the individual.”

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