Saliva tests start to catch on
As the coronavirus pandemic broke out across the country, health care providers and scientists relied on the standard method for detecting respiratory viruses: sticking a long swab deep into the nose to get a sample. The obstacles to implementing such testing on a mass scale quickly became clear.
Among them: Many people were wary of the unpleasant procedure, called a nasopharyngeal swab. It can be performed only by trained health workers, putting them at risk of infection and adding costs. And the swabs and chemicals needed to test for the virus almost immediately were in short supply.
Some places, like Los Angeles County, moved early to self- collected oral swabs of saliva and sputum, with the process supervised at drive-thru testing sites by trained personnel swathed in protective gear. Meanwhile, research
ers began investigating other cheaper, simpler alternatives to the tried-andtrue approach — including dribbling saliva into a test tube.
But the transition has not been immediate. Regulators and scientists are generally cautious about new, unproven technologies and have an understandable bias toward wellestablished protocols.
“Saliva is not a traditional diagnostic f luid,” said Yale microbiologist Anne Wyllie, part of a team whose saliva-based test, called Salivadirect, received emergency use authorization from the Food and Drug Administration in August. “When we were hit by a virus that came out of nowhere, we had to respond with the tools that were available.”
Eight months into the pandemic, the move toward saliva screening is gaining traction, with tens of thousands of people across the country undergoing such testing daily. However, saliva tests still represented only a small percentage of the more than 900,000 tests conducted daily on average at the end of September.
Yale is providing its protocol on an open-source basis and recently designated laboratories in Minnesota,
Florida and New York as capable of performing the test. Besides the Yale test, the FDA has authorized emergency use of several others, including versions developed at Rutgers University, the University of Illinois at Urbana- Champaign, the University of South Carolina and SUNY Upstate Medical University. A further advance, an at-home saliva test, could be headed for FDA authorization, too.
Since the start of the pandemic, the Trump administration’s approach to testing has been hampered by missteps and controversy. As a key health agency during an unprecedented emergency, the FDA’S effectiveness relies on public trust in how it balances the need for speed in authorizing innovative products, like saliva tests and vaccines, with ensuring safety and effectiveness, said Ann Keller, an associate professor of health policy at the University of California-berkeley.
“You obviously want to get new tests into the mix quickly in order to address the emergency, but you still need to uphold your standards,” Keller said. The White House’s public pressure on the FDA has complicated the agency’s efforts by undermining its credibility and independence, she said.
Respiratory viruses colonize areas inside the nasal cavity and at the back of the throat. Besides the nasopharyngeal approach, nasal samples obtained with shorter and less invasive swabs have proven effective for the coronavirus and have become widely adopted, although they also generally require a health care worker’s involvement.
The millions of rapid tests that will be distributed across the country, per a recent White House announcement, rely on nasal swabs.
In the early months of the pandemic, some studies reported significant levels of the virus in oral secretions. In a Hong Kong study published in February, for example, the virus was found in the saliva of 11 of 12 patients with confirmed coronavirus infection.
In Los Angeles, which began using the oral swab test in late March, more than 10,000 samples are collected per day, said Fred Turner, chief executive of Curative, the company that developed it.
Turner sees an advantage to the swabbing strategy. The self-swab procedure takes only 20 to 30 seconds, while producing enough saliva for testing can take people two to three minutes, and sometimes longer, he said. “That might not sound like much difference,” Turner said, “but it is when you’re trying to push 5,000 people through a test site.”