As public-health officials have repeatedly emphasized, widespread testing is one of the cornerstones required for Canada to emerge safely from the lockdown imposed by COVID-19.
In practice, that cornerstone has proved a heavy lift.
Ontario and Quebec, which account for 85 per cent of all Canadian cases of the disease, are testing at rates that are below provincial targets. New Ontario testing guidelines released on Thursday say testing should now be considered for anyone in the province presenting at least one symptom of COVID-19. Alberta has done better at testing a higher proportion of its citizens, including those who show no symptoms but who may have been exposed to the coronavirus that causes the disease.
Per capita, Canada is doing marginally better than the United States, but is well behind some other countries including Germany, New Zealand and Denmark, which for example tests about 60 people per 1,000, twice Canada’s rate. This week in Canada, about 25,000 tests a day were performed across the country, which is less than half of the 60,000 daily tests that should be achievable with current capacity, according to Canada’s Chief Public Health Officer, Theresa Tam.
Yet, even that goal may be too low to contain the virus after physical-distancing measures are lifted, experts say.
A testing action plan issued last month by the New York-based Rockefeller Foundation estimated the United States will need to perform 2.5 to 30 million tests a day to prevent recurring outbreaks. The lower end of that range would require that testing go hand-in-hand with an army of contact tracers that can quickly and precisely chase down emerging clusters of infections.
Those figures imply that Canada, with a population of about one ninth that of the U.S., should be testing at the rate of at least a few hundred thousands a day – far beyond where the country is now – in order to accurately capture the state the pandemic and pave the way for more people to come out of isolation.
But that amount of testing would present problems for the gene-reading equipment that is required to process a COVID-19 test using a method known as qPCR, the current standard in Canada.
“Those machines are just not well suited to scale up and deliver tens or hundreds of thousands of tests per day,” said Paul Hebert, a biologist at the University of Guelph.
Dr. Hebert, who is best known for developing a genetic barcoding system to track ecosystem biodiversity, routinely tests more than one million samples a year in his laboratory alone. His automated system allows him to quickly answer questions such as how many different insects species are present in a trap that contains thousands of specimens.
This week, Dr. Hebert posted a proposal online in which he laid out a way to use his system to vastly expand testing for COVID-19. He said the approach would allow his lab – or any other with the same system – to perform 50,000 tests daily.
“Then we would have the kind of information we need to allow society to re-engage,” Dr. Herbert said.
Importantly, the mass production set-up, known as multiplexing, would deliver results at a cost of about $1 a test, compared with the $40 to $100 price tag for a qPCR test. It would also eliminate some of the supply bottlenecks associated with the chemicals that are needed to perform tests.
Dr. Hebert, who is discussing his idea with provincial health authorities, acknowledged there are regulatory hurdles to overcome before a system that was devised for counting up insect species can be repurposed for human medical samples. But he is not alone in proposing such a scheme. Another team based at the University of Pennsylvania has also laid out plans for a massive parallel testing operation that could handle 19,200 patient samples a run.
Mark Lathrop, director of the McGill Genome Centre in Montreal, said a key barrier to realizing such schemes is simply the logistics of collecting so many samples – typically in the form of nasal swabs – and getting them to a testing facility in time to run them all together.
“I’m not sure how scalable that is with the techniques we’re using now,” Dr. Lathrop said.
Dr. Hebert said sample collecting could become much easier if regulators determine that saliva will work as well as nasal swabs at detecting the presence of virus. It would also allow for group testing. For example, saliva samples from an entire class of schoolchildren could be tested together. Only in cases where such a test came up positive would individual tests of each child be required.
Sample collection may also present a challenge for antibody tests, which do not detect the virus but can determine if someone has been exposed to it. On Tuesday, federal regulators approved the first such test for use in Canada from among a growing list of applicants. The test, manufactured by Italian biotech company DiaSorin, is laboratory-based and requires a blood draw from patients. This makes it unlikely that it will be the test that lets most people know whether they have already had COVID-19.
Timothy Evans, director of McGill University’s school of population and global health, said the newly approved test would still be useful for conducting surveys of sample taken at blood banks and similar settings.
“I’m expecting that there will be other tests coming through which are going to facilitate greater testing at scale,” Dr. Evans said.
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