Dr. Todd Hatchette, service chief for microbiology in the Nova Scotia Health Authority’s central zone, an infectious disease physician and medical biologist, is looking into when and how rapid antigen tests for COVID-19 can be used in the province.
According to Hatchette, the province has 60,000 rapid antigen tests available, but when and where to use them is still being discussed.
Hatchette says these tests can provide a result within 15 minutes, but there are a number of limitations. The most significant is that the accuracy is less than the current PCR swab test being processed by the Province of Nova Scotia’s lab.
“There’s an increased risk for false negative,” he said. “It means a positive test when a virus is circulating is helpful, but a negative test needs to be repeated.”
For that reason, Hatchette says the times when people would be using the test the most is in an outbreak situation, such as in a long-term care facility.
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“There’s lots of discussion about where else to use it. Currently they’re approved for symptomatic people only. So for asymptomatic people, it’s more difficult to know how accurate the test would be in that situation.”
Hatchette says the United States has more experience with these tests because they have been using them a lot, but in Canada it is considered relatively new.
“We’re all struggling, trying to figure out exactly where does that fit in, where is the niche, where this test would actually be helpful. And there are some challenges, in addition to the accuracy that make it difficult to scale up these tests.”
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According to Hatchette, some of the challenges is that rapid antigen tests are only approved for symptomatic people within the first seven days, and it requires a person to take the swab.
“The swab that they’ve been approved for generally is the nasal pharyngeal one, the one that’s a deep nasal swab, which is more uncomfortable than some of the other testing options we have,” he said.
“One of the thoughts is you can overcome this sensitivity issue with repeating the test on a more regular basis.”
But the uncomfortable experience, Hatchette says, may still make the person less compliant in participating in a regular swabbing routine, and will start looking at other testing options.
In the meantime, the gold standard is still considered the lab’s PCR test.
Hatchette says the next step is to ensure that the province has the capacity to meet testing demands, and to do that within an efficient short time frame.
“If we run into an issue with outbreaks, we will look at using these rapid tests to help identify positives. And we always look for opportunities to see how we can leverage these new technologies to try and get ahead of things and look at protecting our most vulnerable.”
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