New cutting-edge rapid test detects both COVID-19 and flu

UC Davis Health has rolled out a groundbreaking, highly accurate test that can check for both COVID-19 and flu viruses at the same time, returning “gold-standard” results in 20 minutes.

Different types of COVID-19 tests explained

Since COVID-19 appeared, testing to detect active infections of the coronavirus has continued to evolve. UC Davis Health expert Nam Tran, professor of laboratory medicine and a member of the California COVID-19 Testing Task Force, explains the range of tests and their uses.

“There can be a lot of confusion about testing,” said Tran. “We want people to be confident they can trust our new point-of-care test just as much as our laboratory test. Both are PCR tests, which is considered the gold standard for testing.”

Diagnostic tests that determine if someone has an active COVID-19 infection fall into two categories: antigen tests, which are mostly used for rapid testing, and molecular and PCR tests.

Antigen tests: Until now, the majority of rapid diagnostic tests have been antigen tests. They are taken with a nasal or throat swab and detect a protein that is part of the coronavirus. These tests are particularly useful for identifying a person who is at or near peak infection. Antigen tests are less expensive and generally faster. The downside is that they can be less accurate.

“You don’t need complex and expensive test kits to detect the antigens,” Tran said. “That makes them cheaper and faster. The problem is, there is a little lag time between when someone gets infected and when the antigens show up.”

That means, if a person is not near peak infection – but is still contagious – the tests may come back negative. Depending on the quality of the antigen test and the test takers, false negatives could be as high as 20%.

“Here’s a good way to look at this,” Tran said. “The coronavirus replicates itself by putting its genetic material inside our cells. If you’re testing that person at the stage when the virus is still replicating inside the cells, it has not produced sufficient protein or shed in large enough amounts to be detected yet by antigen testing.”

The Centers for Disease Control and Prevention (CDC) has advised people who show COVID-19 symptoms but test negative with a rapid antigen test to get a PCR test to confirm the results.

Positive antigen tests are considered much more accurate, but they still can produce false positives. The concern, Tran said, is false positives could be caused by the presence of other viruses, improper collection techniques, or other substances produced by the body during infection interfering with the results. However, he said, antigen testing technology continues to improve.

Molecular/PCR tests: This is another area where there is some confusion. Not all molecular tests use the polymerase chain reaction (PCR), but PCR serves as the mainstay of COVID-19 diagnostic testing. PCR has also become a common shorthand in many media reports.

Molecular tests detect genetic material – the RNA – of the coronavirus and are sensitive enough to need only a very tiny amount of it.

Until now, the best PCR tests generally required trained personnel, specific reagents and expensive machines. The sample is collected with a nasal or throat swab and they tend to take hours to provide results. Good PCR tests like the ones used over the past eight months at UC Davis Health’s lab are close to 100% accurate.

However, not all molecular tests, including PCR methods, are perfect. Some lesser testing platforms have reported false negative rates as high as 15% to 20%.

Both of UC Davis Health’s tests, the rapid COVID-19/flu test and the lab test for COVID-19, are highly sensitive, highly specific PCR tests.

“They are able to pick up very small amounts of viral RNA very early in an infection, so there is a low chance for false negatives, including among pre-symptomatic and asymptomatic COVID-19 cases,” Tran said.

The sensitivity of molecular methods can be a double-edged sword. In some cases, it can still detect the virus’ genetic material after a patient has recovered from a COVID-19 infection and is no longer contagious.

Plus, this coronavirus is still so new to science, nothing is certain.

“PCR is considered the gold standard for many viruses we’ve seen in the past,” Tran said. “But we can’t be certain with SARS-CoV-2. Clearly, we have a lot to learn about this virus and we are all learning in real time.”

Antibody tests: These are not considered diagnostic tests that can determine if someone has an active COVID-19 infection. They use blood samples to look for antibodies produced by a person’s immune system to help fight off COVID-19.

These can detect if someone had a past COVID-19 infection but not if they still are positive for the virus. Tran said antibody tests may have more value once an effective vaccine becomes available.

UC Davis Health is the first in the region and among the first in the nation to use these rapid, combined molecular tests at the point of care. It was one of the institutions that helped evaluate the accuracy of the tests so they could gain emergency use authorization from the U.S. Food and Drug Administration (FDA) and is also the first UC health system to use the test.

“This will change how COVID-19 testing is performed in emergency or urgent care settings,” said Nam Tran, professor of laboratory medicine and UC Davis Health site principal investigator for the clinical validation of the new test. “It can be administered right away by doctors or nurses at a patient’s bedside.”

One valuable aspect is the unique combination of accuracy and speed – qualities that have been somewhat of an either/or choice in COVID-19 testing. Just as important is the ease in administering a single test to detect COVID-19 and both A and B flu viruses. This is crucial with COVID-19 cases on the rise again and flu season looming more dangerously than ever.

“The new rapid test is aimed toward the emergency department or clinics when doctors and other healthcare providers need to make fast treatment decisions,” Tran said.

UC Davis Health, like many other institutions, continues to work with limited supplies of reagents (the chemicals that trigger reactions in tests), so the combined tests will be limited for now to the emergency department or situations when speed is critical. As the supply increases, the testing will continue to expand.

Fast, accurate flu and COVID-19 results can help with management and treatment of both viruses and they can eliminate hours or sometimes days of anxiety for patients.

“There is nothing else right now that is as fast and accurate as this test” said Lydia Pleotis Howell, medical director of the UC Davis Health clinical laboratories and chair of the department of pathology and laboratory medicine. “We have worked hard at UC Davis Health to make sure that all our testing is high performance and meets all the diverse needs of our patients.”

As a member of the California COVID-19 Testing Task Force, Tran is very aware of the demand for speed and accuracy. He’s helped UC Davis Health continue processing hundreds of tests a day for patients, with results coming back often within several hours.

“When patients need results fast, getting accurate results in 20 minutes is a big deal,” Tran agreed. “Some facilities take two to three days for COVID-19 results.”

Lab in a tube

The testing device is made by Roche Diagnostics and is about half the size of a shoebox. It’s called the cobas® Liat® System. Liat stands for lab in a tube. UC Davis Health originally adopted the Liat in 2018 to test for flu and other viruses and bacteria. As the COVID-19 pandemic evolved, UC Davis Health increased its supply of Liat instruments in anticipation of a SARS-CoV-2 test.

“UC Davis Health plans ahead, not just days or weeks, but months,” Howell said. “We even declined early molecular point-of-care tests we didn’t fully trust. We educated our clinicians that we would only adopt a PCR-based method such as Liat that met our standards when the time came. Which is now.”

Roche is the company that also makes the state-of-the-art, large lab “robot” for top-grade COVID-19 tests that UC Davis Health has been using since March, running hundreds of tests a day in the lab, complementing other testing platforms and delivering results in 24 to 48 hours, often less.  

Tran said UC Davis Health ran its own studies on the rapid test and was part of a group of institutions testing Liat’s accuracy in a Roche-sponsored study that was submitted for publication.

“The data support Liat as an excellent alternative to our laboratory methods,” Tran said. “We want people to be confident they can trust the results of this device just as much as our other testing, which is as accurate as anything out there. Both are PCR tests, which is considered the gold standard for testing.”

What are the different types of COVID-19 tests?

Diagnostic tests that determine if someone has an active COVID-19 infection fall into two categories: antigen tests, which are mostly used for rapid testing, and molecular and PCR tests.

Antigen tests: Until now, the majority of rapid diagnostic tests have been antigen tests. They use a nasal or throat swab and detect a protein that is part of the coronavirus. These tests are particularly useful for identifying a person who is at or near peak infection.

Antigen tests are less expensive and generally faster, but also can be less accurate. Depending on the quality of the antigen test and the test takers, false negatives could be as high as 20%.

Molecular/PCR tests: Not all molecular tests utilize the polymerase chain reaction (PCR), but PCR serves as the mainstay of COVID-19 diagnostic testing. PCR has also become a common shorthand in many media reports. Molecular tests detect genetic material – the RNA – of the coronavirus and are sensitive enough to need only a very tiny amount of it.

Until now, the best PCR tests generally required trained personnel, specific reagents and expensive machines. The sample is collected with a nasal or throat swab and they tend to take hours to provide results.

Good PCR tests like the ones used over the past eight months at UC Davis Health’s lab are close to 100% accurate. The new PCR-based Liat has the same high accuracy rate.

Antibody tests: These are not considered diagnostic tests that can determine if someone has an active COVID-19 infection. They use blood samples to look for antibodies produced by a person’s immune system to help fight off COVID-19.

These can detect if someone had a past COVID-19 infection but not if they still are positive for the virus.

Best of class COVID-19 testing at UC Davis Health

Both the rapid COVID-19/flu test and the lab test for COVID-19 are highly sensitive, highly specific PCR tests.

Clinical lab scientists Stacy Yee (left) and Shelley Gillott with the new rapid COVID-19/flu testing device.

“They are able to pick up very small amounts of viral RNA very early in an infection, so there is a low chance for false negatives, including among pre-symptomatic and asymptomatic COVID-19 cases,” Tran said.

“The lab tests we have been using since March are as good as it gets,” Howell said. “They are run in a fully-enclosed robot and operated by highly trained clinical laboratory scientists, so there is little chance of cross-contamination or human error.”

Most UC Davis Health patients will continue to get the lab tests that come back in a day or so because the rapid tests, for now, are being used in the emergency department and in clinics where the results are time sensitive.

Tran said one key to making these tests available to patients has been what he called “our small but mighty point-of-care team.” That would be two people – clinical laboratory scientists Stacy Yee and Shelley Gillott.

Yee and Gillott helped develop the procedures for testing in the clinics and emergency department and worked with the IT team to connect the Liat devices with the electronic medical record system, all while watching over the point-of-care tests throughout the health system.

“They are two of our many unsung lab heroes,” Tran said. “It takes people like them for UC Davis Health to do all the things we do.”

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