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The St. George Care Community long-term care home in Toronto's Annex neighbourhood, in January 2021.Fred Lum/The Globe and Mail

There’s no evidence that routine asymptomatic COVID-19 testing prevents outbreaks in long-term care homes, a new brief from the Ontario COVID-19 Science Advisory Table says, noting the potential harms of using these tests to screen staff likely outweigh the benefits.

In its brief, released Tuesday, the science table found asymptomatic screen testing of Ontario’s long-term care staff identified relatively few positive cases. Yet these tests are costly, place a burden on the province’s labs, risk exacerbating staffing shortages, and can cause pain and discomfort to staff who undergo repeated testing, it said.

“We know that overall, the yield of this testing has been quite low, and we know that there are several direct and indirect harms and opportunity costs of this testing,” said Toronto geriatrician Nathan Stall, a member of the science table who co-wrote the brief.

And given that more than 95 per cent of the province’s long-term care residents and more than 70 per cent of staff have now received at least one dose of a COVID-19 vaccine, Dr. Stall added: “Asymptomatic screen testing is unlikely to be one of those strategies that’s very helpful or high-yield in protecting residents moving forward.”

Routine testing of staff has been thought to help screen out infected staff members who are asymptomatic or presymptomatic and prevent them from bringing the virus into long-term care homes. However, the science table said it found no real-world evidence for this.

It found a total of 705,370 COVID-19 tests were performed on asymptomatic long-term care staff in Ontario between last June and mid-March. These tests yielded 1,147 positive results, for a test positivity rate of 0.16 per cent.

Meanwhile, the science table pointed out several potential harms, including discomfort to staff required to receive frequent nasopharyngeal swabs; the risk of testing fatigue, whereby staff may put off getting tested when symptomatic until their regularly scheduled screen test; and the potential for staff to lower their compliance with other public-health measures if they test negative. It also said staff shortages can be exacerbated by false positives and by staff leaving the sector, especially if they aren’t paid for their time to get tested.

“It’s really not as benign as I think some people make it out to be,” Dr. Stall said.

The science table said laboratory-based PCR tests cost $45 to $50 for each test, in addition to specimen collection, transportation and biomedical waste disposal. In addition, the large volume of tests for long-term care staff “occupies a substantial fraction of the daily provincial testing capacity,” it said.

While rapid antigen tests, which the province has asked that long-term care homes shift toward using, are much less expensive than PCR tests and don’t place a burden on labs, they are less sensitive and therefore must be done two to three times a week in regions with a high incidence of infection, and they require an estimated two additional employees per home to implement them, the science table said.

In an e-mail, Rob McMahon, manager of media relations for the Ministry of Long-Term Care, said the ministry will consult with and act on the advice of Chief Medical Officer of Health David Williams.

“The objective of surveillance testing is to protect vulnerable Ontarians living in long-term care homes by helping to prevent the spread of COVID-19 within homes,” he said. “Point-of-care rapid antigen testing ensures that individuals entering the home can be screened simply and quickly and that positive COVID-19 cases that may otherwise be missed are identified.”

At Toronto’s Baycrest Health Sciences, Scott Ovenden, executive vice-president of clinical programs, said some staff at its long-term care facility, who continue to do weekly PCR tests, do experience discomfort, but many feel reassured by the frequency of screen testing.

Doris Grinspun, chief executive officer of the Registered Nurses’ Association of Ontario, said frequent rapid antigen tests not only don’t prevent outbreaks, they take an “exorbitant amount of time” away from caring for residents.

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