Woman wearing COVID mask studying microscope

BC Should Be Doing More Rapid Testing, Experts Say

By Moira Wyton, The Tyee, Local Journalism Initiative Reporter

As the highly transmissible Omicron variant takes hold, British Columbia is one of the only provinces not making rapid antigen tests  widely available to the public.

Rapid tests can be  administered at home and measure whether someone has COVID-19 and is  likely to infect others. They return results in as little as 15 minutes.

B.C. has received three kinds of tests from  the federal government: Abbott ID Now, Abbott PanBio and BD Veritor.  None are packaged for use at home.

But some 700,000 testing kits could be  deployed for individual use, provincial health officer Dr. Bonnie Henry  has agreed, if boxes were broken down into smaller kits with extra swabs  and solution, as Nova Scotia has done with BD Veritor tests.

As of Dec. 3, B.C. had sent  out almost two million of the more than 3.2 million tests it had  received from the federal government.

About 315,000 tests had actually been used.

Health Minister Adrian Dix said last week  the province uses 35,000 tests weekly. The tests are currently available  to select businesses, non-profits and charities through the province,  and are being used in some remote communities where access to lab-based  testing is limited.

British Columbians can also purchase  at-home rapid test kits for about $40 each at certain pharmacies, while  prices for similar kits online have soared.

Independent experts and doctors in B.C.  have long called for rapid tests to be a bigger part of the province’s  strategy, while Henry has downplayed their usefulness.

“Ideally, they should be made available  freely,” said Dr. Lyne Filiatrault, a former emergency physician who  helped avert the SARS epidemic in Vancouver.

“It is an additional layer of protection we will have to use in B.C.,” she added during a briefing last week with Protect Our Province BC, a group seeking increased testing and faster booster rollouts.

On Tuesday, Henry and Health Minister  Adrian Dix will unveil a new strategy to distribute rapid tests more  widely to the public in the New Year.

The Tyee spoke to three experts about how rapid tests can be used to keep individuals and communities safer.

How do they work?

There are a variety of rapid antigen tests  that all measure whether someone with COVID-19 is infectious to others.  They do this by measuring whether one’s viral load — how much the virus  has replicated in one’s body — is past a certain threshold when the test  is taken.

That means that rapid tests don’t catch  everyone who has been infected with the virus but focus on the subset of  infected people who are contagious to others.

By contrast, molecular polymerase chain  reaction or PCR tests can detect the virus at much lower levels, before,  after and during someone’s infectious period.

B.C. is also asking people only to get PCR tested if they have been exposed or develop symptoms, with long lines for many testing sites in Vancouver being reported as the fifth wave ramps up.

Rapid tests are useful in part because some  people can be infectious without symptoms. Vaccinated people can still  transmit the virus, although at a much lower rate than unvaccinated  people. Early evidence also suggests two doses of vaccine are  significantly less protective than three against the Omicron variant  compared to Delta.

Filiatrault said about 60 per cent of  transmission of COVID-19 happens when someone is asymptomatic, so rapid  tests can help identify more people at risk of infecting others.

“It lowers the risk that you will be  transmitting to anyone else,” said Dr. Victor Leung, an infectious  disease physician in Vancouver. “What it doesn’t say is that you will be  clear from COVID-19 for the next day or few days.”

How accurate are they?

The accuracy of rapid tests is quite high  in terms of identifying someone likely to infect others, regardless of  whether they have symptoms.

The tests will return a positive result, on average across all brands, for 97 per cent of people who could likely infect others. 

For people with viral loads that make them  not likely infectious, rapid tests will be positive between 19 and 63  per cent of the time.

False positives occur in about one to three tests per thousand.

PCR tests, which are required to confirm  illness if someone receives a positive rapid test result in B.C., are  upwards of 99 per cent accurate but can take days to get results back  depending on lab capacity.

Henry has repeatedly said that rapid tests  provide limited benefit when used regularly in the community among  vaccinated, asymptomatic individuals, producing few positive results.

But Leung said just because rapid tests may  identify relatively few cases compared to PCR tests, which are only for  symptomatic or exposed people, doesn’t mean they’re useless.

“If the numbers are so low [with rapid  tests] that you show most people are negative, it gives you more  information,” said Leung. “But if you’re positive, you could potentially  avert a significant superspreading event which would then bring up  transmission rates in the community.”

How should we use them in BC?

Leung, Filitrault and University of Calgary  researcher Gosia Gasperowicz all agree that rapid tests could help  British Columbians have more confidence doing things like working and  visiting relatives for the holidays.

Leung said because viral loads change  quickly as the virus replicates, they are best used directly before  seeing family or heading out to work. 

And with Omicron showing evidence that it  replicates much more quickly than Delta, rapid test results should be  taken as snapshots in time of one’s infectiousness.

“The most effective way to view [rapid  tests] in general, is that they are another tool we have that can  provide a higher level of certainty in the short term, like eight to 12  hours, that you are unlikely to be infectious with COVID-19,” said  Leung.

Gasperowicz said they also shouldn’t be used to justify going to concerts, large social gatherings or other high-risk settings.

“It is not a free pass to do more,” said  the developmental biologist and a researcher at the faculty of nursing  at the University of Calgary. “It’s something that allows you to do with  more confidence what you would do anyway.”

All three experts said other precautions, like good ventilation and quality masks, should be taken when indoors with others.

Leung said rapid tests can help health-care  workers determine if they are infectious as Omicron places more  pressure on the system.

Schools and other environments at high risk  of superspreading should also have priority access to rapid tests. B.C.  has used the tests in a number of outbreak settings already, including  the ongoing outbreak at the University of Victoria.

The experts agree the best approach would  be to make free rapid tests available widely to the public, allowing  people to test themselves each day and make decisions on their  activities.

“In an ideal world, we would distribute  them to as many people as possible and follow that distribution with  very clear education and communication so it minimizes the chance they  are misunderstood and misused,” said Leung. 

Top photo credit: Scientist studying COVID 19 virus by Nenad Stojkovic via Flickr (CC BY SA, 2.0 License)

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