Faster, simpler COVID-19 test uses spit, not swabs
In a shaded parking lot on the University of Wisconsin-Madison campus, so-called spit concierges guide volunteers though giving a saliva sample. On the other side of the parking lot is a pared-down biology lab where scientists test the spit-filled plastic vials for the virus that causes COVID-19.
They’ll have the results within one or two hours.
It’s part of a research effort led by a team with UW-Madison’s AIDS Vaccine Research Laboratory. They are developing a saliva-based test for SARSCoV-2 that eventually could be used for more rapid and accessible COVID-19 testing.
The test, which is based on a method called RT-LAMP, uses saliva samples instead of nose swabs and could help overcome some of the limitations of current COVID-19 testing methods.
Current diagnostic tests detect genetic material from the SARS-CoV-2 virus using a method called PCR, or polymerase chain reaction. Running a PCR analysis requires specialized laboratory equipment that can cycle through different temperatures.
RT-LAMP analysis, which was first reported in 2000 by scientists at the University of Tokyo, also allows researchers to detect genetic material from viruses. However, the method can be performed at a single temperature, obviating the need for expensive, specialized equipment.
Tests can be run where samples are collected — like in a parking lot — and the results can come in a lot faster than when samples need to be sent to a lab.
The materials needed to run the test are also widely available. Dawn Dudley, a scientist in the UW-Madison pathology department who has helped develop the test, says they are unlikely to run into the supply issues encountered with current diagnostic tests.
According to David O’Connor, these features made it “immediately apparent to scientists” early in the pandemic “that a LAMP test for the coronavirus would also be useful.”
O’Connor is a professor of pathology at UW-Madison and one of the lead investigators for this project.
Where RT-LAMP methods fall short is that they can be less sensitive than PCR-based methods. If the amount of viral material in a volunteer’s spit is too low, the RT-LAMP test may not give a positive result.
But O’Connor notes that people who aren’t particularly contagious are the ones who have a low level of the virus. The RT-LAMP test should be sensitive enough to detect the sort of viral loads found in people who are contagious.
“For the purpose of finding people who are highly contagious, the speed almost certainly outweighs any reduction in sensitivity,” said O’Connor. This testing is “more like a fancy fever check.”
Trying to read the colors
The UW team has been running outdoor test stations for the past three weeks at four locations in the Madison area. The test has now been used with more than 1,000 individuals, including UW-Madison athletes and children.
The test’s simplicity also means that there’s a chance that specialized administrators may not be required. A similar program in Racine is training firefighters to run the tests.
Because the test can give results quickly and be run without specialized equipment, the researchers envision that this sort of test could be used to provide frequent COVID-19 tests at businesses or schools.
“There might be a long time when we might want to be able to test people fairly frequently,” Dudley said. “I don’t think this is going to go away.”
Testing people less frequently, such once as every two weeks, “is not enough to really catch people who are infectious,” Dudley said.
Though the team hopes this test will be able to be used as a diagnostic tool for COVID-19 cases, there are regulatory roadblocks. Right now, the test cannot be used to officially confirm a COVID-19 case.
The research team also is still tweaking the testing procedure. Figuring out how it works in a real-world setting rather than the carefully controlled conditions of a laboratory has been the goal of the recent campus tests.
One of the challenges has been getting an accurate reading of the test result.
If one of the RT-LAMP tests is negative, a chemical indicator added to the sample vial remains a rosy pink color. But if there is enough SARS-CoV-2 genetic material, then the sample turns yellow.
The color change makes detecting positive samples straightforward — scientists can quickly look at a sample and determine the result rather than doing more complicated analysis.
But the makeup of peoples’ saliva can affect the colors in the RT-LAMP test, and the final results can sometimes be a confusing shade of orange.
“One of the things we’re trying to do by collecting samples from a variety of people in our research-based study is to understand what that sort of spectrum of colors might look like in truly negative samples,” Dudley said.
Christina Newman, who has been working at the test stations almost every day since they started, said that it now seems a true yellow color is needed for a positive case.
Newman is a scientist with the UWMadison
department of pathology and is trying to fine-tune how the RT-LAMP test works in a field setting.
The team also is working to make the testing process as short as possible, Dudley said. Cutting even five minutes could make a big difference.
“There’s certain little subtleties in the protocol that add a little time here and there,” said Dudley. “Do we have to do them or can we eliminate some?”
The UW team is not alone in these efforts. According to O’Connor, many research groups around the world are working to optimize RT-LAMP for COVID-19 testing.
Just this past weekend, the U.S. Food and Drug Administration approved for emergency use a saliva-based COVID-19 test developed by researchers at Yale in partnership with and funding from the NBA and National Basketball Players Association.
In late June, NBA players who opted into the program began submitting samples for the study.
Right now, it is unclear if and when the UW team’s test method will be able to go beyond the research phase. O’Connor is working with FDA and Medicaid officials to see how this test can be further developed to comply with regulations.