COVID testing plunges in Hamilton
The number of COVID tests being done in Hamilton has plummeted during April and May.
It's a trend seen across Ontario that wreaks havoc with test positivity, which is a key COVID metric.
If you're testing the same sorts and number of people over time, then it's useful to follow the per cent positivity," said Dr. Jeff Kwong, senior scientist at Ontario research institute ICES. Ideally you'd want them to be staying the same."
Instead, the rate has steadily declined in Hamilton from 2,236 per 100,000 population during the week of April 4 to 1,317 on the week of May 16.
As a result, it's hard to know what to make of Hamilton's test positivity that has stayed persistently high while other key COVID metrics dropped. The number of tests coming back positive for COVID was 6.1 per cent Thursday compared to the province's 2.8 per cent.
Hamilton had the third highest test positivity in Ontario during the week of May 16 behind hot spot Peel and Porcupine Health Unit, which declared a state of emergency because of rapid COVID spread in northeastern Ontario.
Making it harder to understand is that Ontario saw testing decreases similar to Hamilton over the same period.
We're seeing the volumes go down and the per cent positivity go down at the same time," said Ontario's chief medical officer of health, Dr. David Williams. I like to see them both go in parallel."
Public health officials and infectious disease experts are at a loss to pinpoint why Hamilton isn't following that trend.
I can't say for sure what is driving our number," said Michelle Baird, director of epidemiology, wellness and communicable disease control at Hamilton public health. I will say it's very possible the right people are being tested - so people who are symptomatic are going in for testing versus the more worried-well."
Attention has shifted to potential differences in who is getting tested in Hamilton instead of how many.
Certain changes are uniform across the province such as fewer kids going to assessment centres since schools closed.
The testing rates kind of plummeted in school-age kids," said Kwong. If your kid has the sniffles or a cough ... when the schools were open, they have to get tested or else they can't go back to school. But now if they're just going to be sitting at home anyway, they're like what's the point."
Testing before surgery is a fraction of what it was provincewide as most elective procedures were postponed. In addition, certain facilities such as some seniors' homes switched to rapid testing instead.
All of the above asymptomatic testing contributes to a low per cent positivity because the results are likely to be negative.
Kwong raised the possibility that the difference in Hamilton could be the same socio-economic barriers to testing in Peel Region.
In Peel, there are language barriers and people work in jobs that they can't get time off to go get tested," he said. If they test positive, they are going to lose two weeks of pay. It depends on so many different factors like if you have paid sick leave or not."
Hamilton assessment centres haven't significantly changed their hours so decreased access is unlikely to be the reason.
There's clearly enough test capacity," said Dr. Zain Chagla, co-medical director of infection control at St. Joseph's Healthcare. Appointments are readily available."
He thinks vaccination is changing individual behaviour around testing. About 65 per cent of adults in Hamilton had a first COVID shot as of Thursday.
People don't get tested post first or second shot of vaccine, given their individual risk of complications are low and so minor symptoms are largely ignored or chalked up to a cold," said Chagla. We have made many diagnosis of COVID-19 in the ER with people with respiratory symptoms after a few days, and it leads to the discovery of multiple individuals within that circle that are positive."
Dr. Dominik Mertz also raised questions about whether those with symptoms or exposure to COVID are seeking testing.
The main concern with high test positivity is that there is a large group of people in a community who are infectious without their knowledge," said Mertz, associate professor in the division of infectious diseases at McMaster University.
He said one clue that Hamilton is on the right track is that hospital admissions have been falling. If significant numbers of cases were being missed, you'd see some of them show up in hospital.
Very ill people will still go and get seen," said Williams.
When determining whether low case counts are real or the result of fewer tests, Williams said one key question is: How are the hospitalization rates? Are they dropping off as well?"
Kwong said the province overall is still in a vulnerable stage" where it's not clear yet what the drop in testing means.
What makes me a little bit nervous is how many undiagnosed cases are there out there in the community," he said.
Joanna Frketich is a Hamilton-based reporter covering health for The Spectator. Reach her via email: jfrketich@thespec.com