'10 times or more': Testing changes mean Alberta's COVID-19 case count is many times greater than reported

Alberta’s chief medical officer of health is underscoring how testing changes are limiting the accuracy of COVID-19 daily case counts as they rise to record levels in an Omicron-driven fifth wave.

Dr. Deena Hinshaw spoke on Monday and introduced a series of new restrictions on who could book a polymerase chain reaction (PCR) test though the province.

She noted that the daily case count number provided by the province has always underestimated the true number of cases, but that the new testing eligibility will lead to further undercounts in the fifth wave.

“It is very clear that our cases are higher than they have ever been before,” she said on Monday.

“In previous waves we’ve seen a range … catching one in four cases, about one in six in the fourth wave. I think it would be a very conservative estimate to say we’re one in 10 or greater at this point in time in the number of cases we are catching.”

Testing eligibility has been restricted by one of age, risk factors, occupation or symptoms for much of the pandemic.

Results from take-home rapid test kits are not included in the province’s daily data updates.

“It’s very clear with a 40 per cent positivity rate that transmission is higher than it’s ever been before,” she said.

“We should assume that at a minimum we’re seeing about 10 times or more the number of cases that we’re diagnosing through PCR.”

Dr. Hinshaw stressed the continued importance of stopping the spread of Omicron despite repeated record-high case counts.

“It is very important to slow the spread to protect the health-care system,” she said.

The diminished utility of case counts means metrics independent of testing become more important indicators, including the number of patients in hospital and intensive care units as well as the number of deaths.

Case counts and test positivity still have some value as leading indicators on whether transmission is increasing or decreasing.

Wastewater testing conducted by the University of Alberta and University of Calgary since May 2020 can also provide some insights into the rate of transmission.

The project tests the wastewater of around 3.2 million people, around three-quarters of the province, spread across 17 wastewater treatment plants and 25 communities across Alberta.