No more nose swabs? Why a saliva test for COVID-19 could be a 'game changer'
Instead of having an extra-long swab pushed way up your nose, you could soon just spit into a cup to get tested for COVID-19.
SalivaDirect, a cheap, saliva-based test for the disease developed by researchers at Yale University, received emergency authorization for use from the U.S. Food and Drug Administration earlier this week. The test was developed with the help of funding from the NBA, National Basketball Players Association and a grant from the Mercatus Center at George Mason University.
Rather than being commercialized and licensed to particular companies, it's being released as an "open source" protocol — a recipe that's freely available for other labs to follow using a variety of commercially available ingredients and equipment.Unfortunately, the test isn't yet available in Canada. But here's why the new test and similar tests under development could be a big step forward in keeping the pandemic under control.
How the SalivaDirect test works
The test detects genetic material or RNA from SARS-CoV-2, the coronavirus that causes COVID-19, using equipment in a lab.
In that way, it's very similar to the nose swab tests that have been the standard for detecting COVID-19 up until now. Because that analysis has to be done in a lab, the results aren't instantaneous — like the traditional test, they'll take about a day to come back.
But the new test has two main differences:
- The RNA is collected from saliva, not a nose swab.
- It skips a step required in standard tests called "nucleic acid extraction," which separates RNA from the sample and requires special chemical ingredients. Instead, it uses a widely available enzyme and heat.
Lab tests comparing SalivaDirect to a traditional nasal swab test found it was only slightly less sensitive, and both types of tests got the same result more than 90 per cent of the time.
Main advantages
Even people who haven't had the test probably aren't enticed by images or video of the nose swabbing procedure.
"We can all agree that it's not a pleasant experience," said Anne Wyllie, associate research scientist at the Yale School of Public Health, part of the team that developed the new test.
The team calls the test "simpler and less invasive" than traditional nasopharyngeal swab tests for COVID-19.
But its advantages go beyond comfort.
In an FDA news release, Admiral Brett G. Giroir, assistant secretary at the U.S. Department of Health and Human Services and its COVID-19 testing co-ordinator, called the new test a "testing innovation game changer that will reduce the demand for scarce testing resources."
That's because:
- The sample can be collected in any sterile container and requires neither nose swabs, which are sometimes in short supply, nor chemicals called nucleic acid preservatives.
- Skipping the nucleic acid extraction step eliminates the need for the chemical kits and reagents, which are also sometimes in short supply. It also reduces the processing time.
- The sample can be collected by the patient him or herself under supervision of a health-care worker. That could potentially lower the risk to health-care workers, who currently have to do the nose swabbing on patients.
- It has already been tested and shown to work with reagents and instruments from different companies. "This flexibility enables continued testing if some vendors encounter supply chain issues, as experienced early in the pandemic," Yale University said in a news release.
- That also makes it cheaper than traditional COVID-19 testing, in addition to being simpler and less invasive. Wyllie estimates the chemical ingredients needed for the test cost less than $4 US ($5.30 Cdn), and she thinks labs could do it for roughly $10 a sample.
· Limited testing, availability so far
· So far, the test has only undergone limited testing in the lab and results have only been published online, prior to peer review, on a few dozen known positive and negative samples.
· "It's really with a small, fairly controlled sample," said Dr. Andrew Morris, a professor of medicine at the University of Toronto and Sinai Health System, who wasn't involved in the research. "We don't know how the test will perform in the real world."
· However, based on that preliminary data, he called the performance "pretty good."
SalivaDirect is currently being tested on the field in partnership with the National Basketball Association and the National Basketball Players Association. Part of the goal is to find out:
- If it's effective for detecting asymptomatic or presymptomatic cases.
- If cases can be detected in "pooled" samples where samples from many individuals are combined for testing at the same time, to see if cases are popping up, for example, on a team or in a workplace.
The test will be offered first at the Yale Pathology Laboratory and at the Jackson Laboratory for Genomic Medicine in Farmington, Conn.
It has not yet been authorized for use in Canada. But Morris says in general, once tests are approved by Health Canada, provinces have been able to scale up pretty rapidly.
Morris notes that SalivaDirect isn't the first saliva test for COVID-19 authorized in the U.S. — the FDA says it's the fifth: "It just appears that this one is easier and doesn't require the [extraction] reagents."
A similar test from Rutgers Clinical Genomics Laboratory and Spectrum Solutions is being used by Major League Baseball.
One U.S. company, DiaCarta, has already submitted its COVID-19 saliva test to Health Canada for review. Health Canada says it hasn't been accepted yet, but the department is working "as quickly as possible."
Potential applications: Schools, workplaces
However, Morris thinks it could lead to wider testing.
"It's been difficult to get people to go to assessment centres," he said. "If they're able to provide a spit sample, it will make it a lot easier for public health officials to get samples from people we need to get it from."
He thinks it has a lot of promise for large populations such as school, college or university students and large workplaces.
Future of saliva tests
Wyllie hopes the saliva test will also be a stepping stone toward faster tests and at-home tests.
Those would be similar to at-home pregnancy tests that provide results within minutes, allowing people to test daily before work or school.
Some such tests are already under development. In Canada, there are teams working on development at the University of Saskatchewan, the University of Regina and Ontario's Western University; Kelowna, B.C.-based Metabolic Insights; and Victoria-based ImmunoPrecise Antibodies in collaboration with the University of Victoria.