By Allison Martell

TORONTO (Reuters) – Ontario, Canada’s most heavily populated region, has been lagging other Canadian provinces in testing for the coronavirus because in the early weeks of the outbreak its public labs relied heavily on a single company for needed chemicals.

The province is ramping testing back up, focused on finding patients who could have had the largest impact on others, such as healthcare workers. But the slowdown led to thousands of backlogged tests.

“There are real restrictions on who is being tested, so test results are not a real accurate measure of how widespread the infection is,” said Jane Philpott, a former federal health minister and doctor who is doing clinical work.

“There’s an unknown number of people who have had respiratory symptoms and probably had COVID infections that have not been tested.”

As of Wednesday, Ontario had tested 4,188 per million residents, less than every Canadian province except New Brunswick and Prince Edward Island, which have far fewer cases. Alberta had tested 11,139 per million, and Quebec 8,216 per million.

The provincial public health agency’s labs were heavily dependent on one company’s system to extract RNA, the virus’ genetic material, the agency told Reuters.

Global shortages of chemicals have slowed coronavirus testing elsewhere. A handful of companies make most RNA extraction equipment, and sell reagent kits made for their own machines. Labs that rely too much on one company are vulnerable to reagent shortages.

Public Health Ontario’s lab system has “since diversified to two other (companies)” said its chief of medical microbiology Vanessa Allen.

It was not clear why the province had relied on a single reagent provider, while others had fall back options.

“When we plan for clinical labs, good practice is that you have redundancy all over the place,” François Rousseau, head of the department of laboratory medicine at the hospital group CHU de Québec-Université Laval in Quebec City.

“Then when you are stalled with one provider, you can turn around and send your samples to the other equipment or the other facility.”

In a statement, Public Health Ontario said it was not unusual for labs to have a primary platform, noting the level of reagents needed during the pandemic was “unparalleled”, overwhelming its system.

In a May 2017 planning document, the agency said its funding had been flat for five years, despite increasing test volumes. It flagged lack of funding as a risk to its “ability to comprehensively respond to emerging public health threats.”

Alberta, which leads the country in per capita testing, has two testing workflows on different equipment, using different reagents.

Quebec’s labs do not rely on any one company’s products either, its health ministry said in a statement, but the province is also working to further diversify, and may revise some techniques to limit its use of certain reagents.

(Additional reporting by Tessa Vikander in Vancouver and Anna Mehler Paperny in Toronto; Editing by Amran Abocar)