rapid testing found at least 10% of n.s. cases in its third wave
unlike most provinces which reserve testing only for symptomatic people, nova scotia's pop-up centres allow asymptomatic people to simply show up and get a free rapid test
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by: brian platt
while rapid testing remains sorely underused in most of canada, one province has been innovating with rapid tests from the very beginning — and is now reaping the benefit.
during the third wave that hit nova scotia over the past month, the province’s community rapid testing centres have correctly sniffed out at least 285 covid-19 cases in asymptomatic people, or about 10 per cent of all confirmed cases in this time period, according to the nova scotia health authority.
while most provinces reserve testing only for symptomatic people or close contacts of a case, nova scotia’s pop-up centres allow asymptomatic people to simply show up and get a rapid test for free, with results sent to them within an hour. the whole process relies largely on volunteers without a health-care background.
furthermore, the true number of cases credited to rapid testing is probably much higher. when a rapid test correctly identifies a positive case, the person’s close contacts such as their family get pcr lab tests that don’t show up in the rapid test statistics.
lisa barrett, an infectious diseases specialist and the driving force behind the rapid testing program, said it’s hard to say for certain, but taken altogether she estimates rapid antigen testing has helped nova scotia find about 18 per cent of all cases during the third wave.
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“this is the early detection system,” barrett said. rapid testing tends to catch people early on in their infection when they’re full of virus, meaning positive cases are found and put into isolation fast — likely days before they would have been found with a pcr test, if they were found at all.
the program’s success stands in stark contrast to other provinces, where community rapid testing is effectively non-existent due to excessive regulation and enduring skepticism about rapid testing by some health officials. barrett estimates that at its peak level, nova scotia was running 8,500 rapid tests per day on asymptomatic people; the equivalent in ontario would be 127,500 daily rapid tests.
while things could still change, it appears nova scotia has bent the curve on its wave relatively quickly, with cases heading back downward. “if you take our uptick, peak, duration and downslope, and you lay it over other provinces, it’s looking good,” barrett said.
until recently, nova scotia had largely escaped the worst of the pandemic, but that changed in late april when the more transmissible variants caused an outbreak. in response, the government imposed a lockdown and scaled up its testing — including the pop-up rapid testing program that first started in november.
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for the most part, the pop-up centres have been a community engagement project rather than a large-scale screening program. with nova scotia’s case counts very low over the winter, the centres were mostly a way to get people comfortable with being tested regularly, and to work out the operational kinks. barrett said they now have 2,300 volunteers on their list to help run the centres.
but when the outbreak hit, the rapid testing kicked into high gear, especially in hot spots such as the halifax region. on any given day, about eight rapid testing centres might be running, some of them by barrett’s team and some by praxes medical group on a contract from the province. the centres use the abbott panbio device, and positive results are confirmed with a pcr lab test.
barrett said most people who test positive on a rapid test are shocked to learn the result, given they had no symptoms.
“most people are like: i have no idea how this could have happened, i feel perfect,” barrett said. she said it will take more time and evidence before we know for sure with the variants, but all indications are that people can be very infectious in this early asymptomatic phase.
john ross, medical director at praxes, said he’s seen it happen multiple times now where an asymptomatic person has tested positive on a rapid test, and then developed symptoms the next day. if they had waited until they developed symptoms to get a pcr test, and then waited another 24 hours until they got the pcr results, that’s at least two days where they might have been unknowingly spreading the virus.
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“we know that the rapid tests, it may not be quite as sensitive as a pcr test, but it picks up people at that most infectious on-set time period,” ross said. “so it’s actually still a really good test for that purpose.”
ross said his experience so far is that about one in 1,000 rapid tests turns up a false positive, meaning the subsequent pcr test returns negative. overall, he said this has been a non-issue for them since they confirm every positive test with a pcr test regardless.
nova scotia’s experience does not mean rapid testing is a silver bullet to stop a pandemic. the backbone of the testing system is still the extremely accurate pcr test, and the province still needed a lockdown to reduce people’s social contacts. but the pop-up centres show that rapid tests are effective at finding cases that might otherwise be missed; the program will likely allow nova scotia to reopen more quickly.
the success of the program is also further proof that it’s unnecessary to insist on medical precision for rapid tests. while other provinces are only now repealing regulations that restricted rapid test operation to nurses or other health-care professionals, nova scotia has been running rapid tests with lay volunteers since the fall. in fact, the program’s operators prefer that they not be referred to as pop-up “clinics,” given the medical connotations of the term.
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“it is remarkably empowering for so many people to be able to be part of something to keep their own community safe,” said susan helliwell, chief executive officer at praxes. “being a non-medical event has been a huge part of its success in rolling out with communities and making them feel safe.”
barrett said that above all, the point is to just get the tests done, and to encourage people to continue getting tested regularly even as case numbers drop.
“this is not just about numbers and finding cases,” she said. “we’re promoting serial testing. we’re not promoting: come and get one test during a peak wave. we’re promoting: every week a test.”
• email: bplatt@postmedia.com | twitter: btaplatt
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