Canadians seeking a COVID-19 PCR test in recent days may have faced long lineups at testing centres and a shortage of appointment slots as demand has risen amid the spread of the Omicron variant.

The surge in tests has created a backlog in certain provinces, which in some cases has led to an adjustment in testing protocols.

Ontario was scheduled to announce new testing guidelines on Tuesday, but the update was postponed until later this week.

In a statement to CTVNews.ca, Ontario Health said, as of Dec. 27, labs were completing 53 per cent of PCR tests within one day of collection and 82 per cent within two days. While the lab network has the capacity to complete 100,000 PCR tests daily, the agency said turnaround times are likely to continue to rise as volumes increase.

"We understand that COVID-19 assessment centres, community testing sites and hospitals in some communities are experiencing increased wait times for testing appointments," the agency said. "We are working with them as needed to meet community demands and align with the lab network's testing capacity."

The agency added it's working on a number of strategies to optimize collection processes.

Testing centres in Quebec have also been overwhelmed. During a news conference Tuesday, the head of the province's the vaccination program, Daniel Paré, said the centres are at "maximum capacity" now and PCR testing should only be sought by people who have COVID-19 symptoms.

"People have to isolate when they're symptomatic and take these basic precautions. And for those who have rapid tests, use them well," he said.

As of Dec. 27, PCR testing for the virus in Nova Scotia has been limited to people deemed high-risk. Only those who have symptoms or are close contacts and are at increased risk of severe disease, live in congregate settings or are front-line health-care workers are eligible.

All other Nova Scotians who experience symptoms or are close contacts can book an appointment to pick up a take-home rapid testing kit.

Manitoba, as of Dec. 27, also has changed how it administers COVID-19 testing. People who visit a testing site and are symptomatic as well as vaccinated will receive a take-home rapid testing kit. Those who are symptomatic and unvaccinated are eligible for a PCR test, with those deemed high-risk also being given a take-home rapid testing kit.

Dr. Brent Roussin, the chief provincial public health officer, said with the current testing backlog that people under 40 years of age with no underlying health conditions may want to consider self-isolating for 10 days if they develop symptoms.

On Friday, British Columbia announced the province had reached its capacity for processing COVID-19 PCR tests, which is about 20,000 per day, and that it would begin to prioritize such testing for people at greater risk of complications from the virus. This includes those who are aged 65 and up, have weakened immune systems or experiencing severe symptoms. PCR tests are also being reserved for front-line health-care workers.

Provincial health officer Dr. Bonnie Henry also said anybody who has COVID-19 symptoms should assume they have the virus and self-isolate for a week if they're vaccinated or 10 days if they've had less than two vaccine doses.

With files from CTVNews's Joe Lofaro, Natalie Lombard, Sarah Plowman, Mason DePatie and Ian Holliday, and CP24's Chris Herhalt