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A simple mouth swab and rinse with testing technology adapted from a common viral detection method – the pap smear – could provide an easy, low cost and rapid diagnostic tool for COVID-19 infections, according to researchers at the University of Toronto.

Michael Glogauer, professor at the university’s Faculty of Dentistry and head of dental oncology at Princess Margaret Cancer Centre, is working with partners at Sunnybrook Health Sciences Centre, North York General Hospital, Sinai Health Systems and the University Health Network to research the viability of the platform.

The novel coronavirus that causes COVID-19 infections invades epithelial cells, such as those lining the lungs. But these epithelial cells are also prevalent in large numbers in the mouth, and especially on the tongue, where respiratory droplets are expelled. COVID-19 binds to the body’s epithelial cells through ACE-2 receptors – and, as Glogauer notes, “It just so happens that the tongue expresses extremely high levels of ACE-2 receptors.”

That makes the mouth, which is also one of the most easily accessible sites on the body – requiring no needles, and, unlike the nose, causing no pain when swabbed – an ideal place from which to cull samples.

“The tongue is a big net,” says Glogauer. “It will always be positive if an infection is present.”  

Recently, Canada has launched a number of detection platforms to help with the fight against COVID-19. Some proposed detection methods require specialized technology or equipment. Others, like the common nasopharyngeal swab method, utilize certain chemicals for testing that are currently in short supply around the world.

But Glogauer says there’s a testing platform already in use which could make a significant difference in making COVID-19 testing more widely available: the pap smear.

“Pap smears show viral changes and inflammation in epithelial cells,” he says, adding that’s what technicians are on the hunt for with COVID-19.  

The test is also routine and simple: epithelial cells are scraped, mounted onto slides, stained and viewed under a microscope. The cost? Approximately $30 per test.

Glogauer adds that laboratories across Canada could rapidly employ the platform.

“All labs are set up to do pap smears,” he says.

The process of adapting the test would be virtually painless, too. Samples could be easily collected by giving subjects an oral rinse and brushing their tongue. Results can be returned in a matter of hours. Importantly, the smear test could represent an easy ally for COVID-19 detection in developing nations, where lab technology is limited.

“If it works, it will be a real game changer for everyone,” Glogauer says.

While Glogauer cautions that the technology needs to be fine-tuned in order to prevent false positives, he says there’s significant potential to develop a fast and relatively inexpensive tool in the arsenal to find and detect COVID-19.

“Ideally, you want different testing modalities,” says Glogauer. “This could be one of them.”