More robust COVID-19 testing system needed in Canada, say experts

Experts say Canada needs to develop a robust system to detect COVID-19 activity in the absence of wide-scale PCR testing.

Since the onset of the Omicron variant, provinces and territories have scaled back access to gold-standard PCR testing, citing the lack of capacity to keep up with demand and the need to free up health-care resources.

Many people have since relied on results from rapid antigen tests, but they aren't as reliable at detecting the Omicron variant, nor are they reported and tracked the way PCR tests are. Experts say there needs to be a better way of informing people about COVID-19 activity in their communities.

Dr. Caroline Colijn, a mathematician and epidemiologist at Simon Fraser University, said there are currently "too many infections" in Canada to expand access to PCR tests to everyone to find out the true number of infections.

She said more robust programs could also be used to pick up other kinds of respiratory infections.

"And I suspect those are under development, but until they're developed, deployed, and results are publicly available, people will have trouble finding out what their risks are in their social group, in their community and in their workplace," she said.

"So then they'll have trouble having the information needed to inform their own choices, their own workplace or community policies."

Colijn said wastewater data is a really important source of information that can be publicly shared without compromising anyone's private medical data and can help communities understand the prevalence of COVID-19. But like PCR and rapid tests, she said it has its limitations.

She noted there are numerous factors that could change wastewater signals, such as rainfall, temperature and different variants leaving different amounts of sequencing in the water, resulting in less accurate COVID-19 case estimates.

Colijn said she anticipates an integrated system that would incorporate wastewater data, along with PCR and rapid test results, in a way that's designed to paint a more accurate picture of how much COVID-19 is in a population and inform people about the risk of contracting the virus.

"So we do need to think about how to get representative samples, and how to understand how many infections are out there," she said.

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Dr. Dan Gregson, an infectious disease physician and medical microbiologist at the University of Calgary, said it would be reasonable to expand PCR testing access to certain settings like schools and long-term care homes in the event of an outbreak so they can make a decision on whether to close those institutions to prevent further transmission.

However, he said the average person can rely on wastewater data to assess the risk of contracting COVID-19 in their community since it's "much more cost-effective" and "tells us similar information" to PCR testing.