Dip in weekend testings risks further spread
Samples lull making it harder to interpret trajectory of second wave
Hundreds of COVID-19 infections may be going undetected each week in Ontario because the province is regularly failing to use its full capacity to test for the disease, experts warn.
The problem is a weekly pattern that’s been clear since the spring: Far fewer Ontarians are getting tested on the weekend.
This, in turn, has led to a weekly up-down testing cycle that may be making it harder to control what’s happening in Ontario’s second wave, says Dionne Aleman, a University of Toronto professor and an expert in pandemic modelling. If thousands fewer patients’ samples are being collected on the weekend, it suggests possibly infected people may be waiting to get tested, which leaves more time for them to expose other people, she said. “That’s a lot of secondary infections that have happened all because somebody didn’t want to come in on the weekend.”
She added that if testing could be brought to the same numbers as weekday testing, that’s probably “at least another 20,000 tests in a week that can be processed.”
Ontario’s per cent positivity rate — the share of tests that come back positive — has been increasing since September and hit a second-wave high of about 3.5 per cent this week. At around four per cent positivity — a rate Toronto is already hitting — those uncollected tests would work out to “800 more infections that can be confirmed and isolated each week,” Aleman said. “That’s a big deal.”
The weekly pattern has been apparent through almost the entire pandemic: Since May, about 16,000 new samples have been collected on an average Sunday — the low day in the weekly cycle. A typical Wednesday — the high day — has seen nearly twice as many samples collected, at an average of nearly 32,000.
As a result of this weekend lull, Ontario’s testing labs tend to start each week with far fewer samples on hand to process. An average Monday since May has seen about 21,000 tests completed daily, nearly10,000 fewer than an average Friday.
Months after Ontario’s first wave, this pattern still shows up in the province’s daily reports, a fact that may be making it more difficult to interpret the trajectory of the second wave: On Tuesday morning, the province reported 827 new COVID-19 cases, well down from the record total of 1,042 from two days earlier — but was that drop a real sign fewer people were getting the virus, or was it just that the labs analyzed 15,000 fewer samples on Monday?
(By the rate of positives per completed tests, Tuesday’s number was actually significantly worse than the singleday record, at 3.5 per cent positive vs. 3.0 per cent.)
The province says its labs can process around 50,000 samples daily. On Monday, they processed less than half that, just 23,945.
“The COVID-19 testing strategy has been and remains a weak link in Ontario’s pandemic response,” said Ahmed Al-Jaishi, an epidemiologist and PhD candidate in health research methodology at McMaster University. The fact that many assessment centres have reduced hours of operation on weekends, coupled with the requirement to make an appointment for a test “seems counterintuitive and disproportionally discriminates against people that are unable to access testing centres on weekdays for reasons like shift work, school, and child care, or do not have reliable or regular access to the internet,” Al-Jaishi said.
Ontario Health, the central provincial agency responsible for testing, says the regular drop in lab output is caused by testing demand that “seems to drop off over the weekend and pick up as the week goes on.”
Asked what specifically the province is doing to increase the number of people coming in for testing, Ontario Health spokesperson Jennifer Schipper said: “Testing capacity is not a target; it is the ability to process the tests coming in and in accordance with the testing guidance.”
Nevertheless, the province “continues to prioritize areas where there is a higher prevalence of cases,” she said, adding that testing efforts are underway or planned in a series of hard-hit areas, including in the specific Toronto neighbourhoods of Rexdale and Black Creek.
While Premier Doug Ford said last week “we can’t force people to come in for a test,” Al-Jaishi said the government could make it easier for people to get tested through measures such as making walk-in testing available, flexible assessment centre hours and more mobile clinics for hard-hit neighbourhoods.
Dr. Samir Sinha, director of geriatrics at Sinai Health System and University Health Network in Toronto, says Ontario needs a “clear road map” for what the province is trying to accomplish with testing.
“We’ve swung from one way of the government being concerned that not enough people were going to get tested, to then opening the floodgates by saying anybody who wants a test for any reason can go get a test,” he said. “And now we’ve kind of complicated the situation by saying asymptomatic people have to go get tested at a pharmacy, for example, and then people who are symptomatic can go to a COVID assessment centre.”
Sinha said he hopes next week’s provincial budget will include funding to hire an “army of contact tracers” that can be deployed to areas experiencing outbreaks, noting that testing without tracing doesn’t fix the issue.
“I think this is where there is a huge opportunity,” he said. “They can be our mobile strike force.”