Asymptomatic tests not a priority

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This article was published 21/06/2020 (1659 days ago), so information in it may no longer be current.

OTTAWA — Alberta has been testing far more asymptomatic people for COVID-19 than Manitoba, on a proportional basis. But a local expert says those testing rates likely reflect each province’s needs.

A Free Press survey of testing data shows that all three Prairie provinces are testing for the coronavirus far below their capacity, likely in an effort to save resources for a second wave. In Manitoba, officials also point to the unreliability of test results among asymptomatic people.

Since the start of the pandemic until June 16, Alberta had tested 28,156 asymptomatic people with no known COVID-19 exposure, both at targeted locations and part of population monitoring.

The province could not say how many of those tests occurred after June 2, when Alberta expanded testing from select risk groups to anyone wishing to be tested.

Manitoba allowed asymptomatic people to get tested as of May 20. The province has targeted truckers returning from outside of Manitoba and people admitted to hospital for reasons other than COVID-19, to see if undetected community spread is underway.

Manitoba had done 4,700 tests on those two target groups as of June 16. The province did not provide data on how many asymptomatic people had gone to a testing centre on their own accord, and received a test.

On May 25, Saskatchewan expanded testing to anyone working outside their home who wants one, after weeks of restricting tests to only people with symptoms. Like Alberta, Saskatchewan still requires people to get a referral to have a test done.

A Saskatchewan spokeswoman said that province had referred more than 1,500 asymptomatic people for testing as of June 17, but did not know how many had been done.

Saskatchewan has said it can complete 1,500 tests per day, but is doing about one-third of that. The province has prepared a mobile facility to test at factories and other high-density workplaces, though it appears it won’t be pressed into service unless there is an outbreak.

Alberta is on track to be able to test 16,000 people in a day, though it’s currently testing between one-third and one-half that amount.

Manitoba plans to be able to test 3,000 people per day by the end of the summer, because of its partnership with private lab Dynacare. But it hasn’t yet done 900 tests in a single day, and often completes half that number.

Dr. Brent Roussin, Manitoba’s chief public health officer, has played down the idea of testing a lot of people who don’t have symptoms, because results can come up negative even though they have the virus, only to have symptoms appear a day later.

The Prairie provinces are similar to the rest of Canada and other countries, according to an extensive June 2 analysis of how jurisdictions decide which asymptomatic people to test.

The review by McMaster University’s Health Forum found that as of two weeks ago, most provinces were limiting testing of asymptomatic people to those who had contact with a positive COVID-19 case, residents and staff of long-term care facilities or jails, and those being admitted to hospitals.

Literature correlated by the Hamilton university shows almost every jurisdiction focuses asymptomatic testing on high-risk groups.

Countries hailed for widespread testing, such as Germany and South Korea, conduct aggressive contact-tracing and testing of people possibly exposed to an infected person, instead of widespread public testing, the analysis found.

Weighted by population, Alberta has tested almost twice as many asymptomatic citizens as Manitoba, though Alberta has had more recent outbreaks of COVID-19 than Manitoba.

Meanwhile, Manitoba’s asymptomatic testing rate is, per capita, 2.5 times higher than that of Saskatchewan.

Dr. Yoav Keynan, a microbiology professor at the University of Manitoba, said it doesn’t make sense to do widespread testing of asymptomatic people when there isn’t a lot of community spread.

“It depends on where the epidemic is in that jurisdiction” Keynan said. “There are costs in terms of operating a system of intensive testing, in terms of personnel and reagent. You basically have to balance exhausting resources that you’re going to need if you’re going to have more cases — for testing that has very low yields.”

For example, Alberta’s more than 28,000 asymptomatic tests discovered just 10 cases of COVID-19 out of the province’s 7,530 cases, as of June 16.

dylan.robertson@freepress.mb.ca

McMaster University report on asymptomatic testing approaches