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What you need to know about COVID-19: May 29
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In virtually every strategy for reopening pulverized economies, turning the lights back on will require rapid, aggressive testing — tests to diagnose new and active infections, trace contacts and quickly quarantine the exposed to contain the virus, and tests to provide a better grip on just how much the virus has already churned through the population. The National Post’s Sharon Kirkey spoke to John Brennan, a professor in the department of chemistry and chemistry biology at McMaster University, and Cameron Groome, CEO and President of Microbix Biosystems Inc. about the state of COVID-19 testing — what’s available now and what’s on the horizon.
The swab test
First, a long swab is inserted deep into the nose to the nasopharynx, the upper part of the throat behind the nose. The swab has to be swished around enough to collect a sufficient sample of cells, mucus and, potentially, virus. It can cause nosebleeds in some people.
“Once you have the sample, you have to bust the virus open,” Brennan said. The sample is placed inside a container of chemicals that cause the virus to rupture and release the viral RNA in those cells. That genetic material is then turned from RNA into DNA, using a process called reverse transcription and an enzyme called reverse transcriptase.
The DNA then has to be amplified to provide enough of a signal to determine if the virus is present.
The sample from the nasal swab is normally put into a storage solution and shipped off to a laboratory, where it can sit around for days before it finally gets tested.
That’s one significant delay. The tests also rely on a sufficient supply of swabs, which are in seriously short supply. So is the enzyme that converts RNA to DNA.
“So building another test that uses the same methods — swabs and reverse transcription — is never going to go anywhere, because you’ll never get the supply chain set up so that you can get the reagents to do it,” Brennan said. “This is not something that can ultimately be ramped up to the level it needs to be.”
Some have suggested that the U.S. alone would need a mind-blowing 20 million tests a day, though Brennan tends not to believe this. Canada could require at least 100,000, and perhaps as many as 500,000 tests a day to really be able to test all people with symptoms and a large proportion of “asymptomatic” carriers.
Home test kits
Brennan and his McMaster colleagues are trying to get around the bottlenecks by moving testing away from central labs into the home, with a test that could be done in as few steps as possible to minimize errors.
The hope is to have a home testing kit ready to be scaled up within three to four months and pushed out before a second wave hits.
Ottawa-based Spartan Bioscience is developing a portable testing kit that uses a hand-held DNA analyzer, doesn’t require specialized expertise and could provide results in less than an hour.
No test is 100 per cent perfect, but there are reports of false negatives being as high as 30 per cent. False negatives are a particularly insidious problem, and testing can be finicky, says Groome, whose company has just received Health Canada approval for a new quality assurance product that will help weed out false positives and false negatives in future COVID-19 tests.
When tests fail it’s often because the amount of virus picked up by the swab wasn’t sufficient. The person might be infected, but too early, or too late, in the infection to have enough material to test positive. If someone is told they’re negative when they are not, they risk casually infecting other people.
Some governments have floated the idea of testing people for antibodies to the SARS-CoV-2 virus that causes COVID-19 and issuing an “immunity passport” that would let people travel or return to work, assuming they’re protected against re-infection. But it’s not known what level of protection recovered people have, or how long immunity might last.
Also called serology tests, antibody tests are conducted on blood samples, usually from a finger prick that looks for antibodies that latch on to the virus. The first on the scene are IgM antibodies that appear within a week of the body being infected by a foreign substance. Later, a more durable antibody called IgG is produced and it is thought to be detectable after about two weeks.
Several companies are producing antibody tests. Roche Canada hopes to have its Elecsys Anti-SARS-CoV-2 test available for Canadian labs by the end of May or early June.
Broad testing of random samples of the population could give us a sense of how many Canadians have been infected, as well as how many asymptomatics are running around. The federal government has launched an “immunity taskforce” to figure out how widely the virus has spread in Canada and what that means.
“If somebody has antibodies, does that mean they’re immune? We don’t know yet,” Brennan said.
Quebec premier Francois Legault has mused about herd immunity, the idea of letting the young and healthy out of lockdown and keeping the susceptible sheltered.
“There are a lot of complete unknowns where people are saying, ‘let’s try this and we’ll wait two or three weeks to see if people are getting infected,’” Brennan said.
“Nobody knows if that’s going to work, or if sending people out now is going to trigger a massive second wave in June.”
Copyright Postmedia Network Inc., 2020