In early spring of 2020, as the pandemic was beginning to send much of University of Wisconsin faculty and students to work remotely, UW biomedical engineering Ph.D. student Duane Juang became aware of major gaps in the U.S. health response, specifically in adequate numbers and availability of testing materials, through a Politico article.
The article warned about the potential inability of public health labs across the U.S. to support unprecedented demands of COVID-19 testing supplies and specific instrumentation. The concerns would become reality as new waves stressed testing sites across the nation.
This lack of sustainable infrastructure for quick and accurate testing throughout the COVID-19 pandemic motivated Juang and other UW researchers to find an alternative to the “gold standard” that is PCR testing, as well as to promote the advantages of serial antigen testing.
At the time the pandemic hit, Juang’s primary research focused on microfluidic technology and assay development — a form of composition testing. But his research turned out to have another use, and it aided him in adapting some of his lab’s existing technology to perform the assays required for COVID-19 testing. A little over a year later, Juang and his team were able to get their work published, which he is using to develop a cheaper and faster alternative to PCR testing.
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Juang, currently doing his postdoctoral work at UW, is working on modifying the technology to be used for point-of-care testing at home rather than pushing it toward large-scale, centralized testing.
“I came to the realization that there are actually a lot of people working on centralized testing, there’s a lot of research and companies doing it,” Juang said. “I later found that maybe our efforts are better focused at developing an at-home molecular test … there are much fewer players in that market, which I think is really important.”
Though there are now a variety of antigen tests available, they are simply not at the level of sensitivity that PCR tests offer. Juang said the goal is to develop a test as sensitive as a PCR but one that maintains the low cost and simplicity of an antigen test.
According to the University of Massachusetts Chan Medical School, one of the main differences between a PCR and antigen test is that PCR detects the nucleic acids, or genetic information, of a given pathogen, such as SARS-CoV-2, which causes COVID-19. This is done through RNA extraction from a swab or saliva sample, followed by a technique of washing and elution to get the RNA in its most purified form. Finally, a process called polymerase chain reaction, or PCR, is used to amplify the SARS-CoV-2 genetic material, allowing for detection of even the smallest amounts of the virus with high levels of accuracy.
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According to the UMass Chan Medical School article, antigen testing takes on a much quicker approach. Its test strip contains antibodies, a form of immune response the body produces when in contact with an antigen, specific to SARS-CoV-2, painted on a thin line. After adding a sample containing the virus, these antibodies bind to the coronavirus antigens, producing a second colored line and indicating a positive test result.
Despite being quick, easy-to-use and relatively inexpensive, the UMass article explains that antigen tests have drawbacks. Unlike molecular PCR tests, these tests do not use amplification of the virus as the detection method. So if a person is asymptomatic or in the early stages of infection, during which there is less virus found in the nose and throat, false negative results are common.
David O’Connor, a UW professor of pathology and laboratory medicine, said that despite these drawbacks, antigen tests are now being heavily encouraged for large-scale testing at universities and K-12 schools because of proven accuracy when done within the span of a couple of days.
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“It’s true that a single antigen test doesn’t have the same limit of detection at the very low end. But if you give the virus a couple of days to replicate, then your antigen test is going to have every bit as good a sensitivity as the PCR,” O’Connor said. “Taking two antigen tests 48 hours apart might be more sensitive than taking a single PCR or a single lab test.”
UW’s own testing regime for this semester relies on ramped-up accessibility to free antigen tests. Beginning Jan. 25, UW implemented the distribution of antigen tests to all students and employees, currently allotting one free kit per week, as well as maintaining the previous fall semester PCR test capacity at 5,000 per week consolidated at one testing site down from four last semester.
O’Connor said that these simple, low-cost, self-administered tests have enormous advantages over all other types of tests because of how easy and convenient they are. He encouraged students to take advantage of university testing resources, as well as self-report positive results to help put public health in a better position to respond to an ever-changing pandemic landscape.
Juang also maintains the drawbacks of PCR testing as he presents why his test — named OIL-TAS — has the potential to be cheaper, faster, easier to deploy and with a performance rate nearing that of PCR molecular tests.
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“The only things you need are pipettes, your reagent [the device], a shaker, an oven and a method to capture images of the device,” Juang said. “We use a scanner, but you can actually use your phone. You don’t need a PCR machine or any optical detectors, so that makes the assay a lot cheaper to run.”
According to Juang, the OIL-TAS conserves the number of pipette tips required in PCR testing, eliminating the need for multiple pipette washes, which substantially lowers the high levels of plastic byproduct that is seen with other large-scale molecular testing methods. It also uses a much less complicated assay, meaning procedural steps consist only of pulling a magnet across the bottom of the device, performing everything from sequential washing all the way to detection. Jaung said the OIL-TAS is also not constrained by the current supply of specialized instruments or traditional reagents — a common concern with other forms of lab testing.
Juang’s published report explains the OIL-TAS shows opportunity for future testing to be done using similar microfluidic technology. His report shows the OIL-TAS cuts down on the need for expensive instrumentation and lowers reaction time to 30 minutes, providing an overall user-friendly assay and showing a 93% accuracy for positive results.
O’Connor said the OIL-TAS technology has the potential to be a molecular test with a very fast turnaround — something he says the system continues to struggle with in molecular testing.
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“I think of it as one of many types of molecular tests that are going to coexist into the future, helpful for COVID and for other things,” O’Connor said.
As for the future of this technology, Juang said his team has received two patents covering the core technology of their COVID-19 tests. He also mentioned two specific tests that utilize similar microfluidic systems that received FDA approval since the start of the pandemic.
“It’s good to see my field of microfluidics making good progress and benefiting people,” Juang said. “And it’s nice to see some of those goals starting to become realized.”
