New COVID-19 Test Only Needs Saliva and Yields Results in 45 Minutes: Study
Wed, April 14, 2021

New COVID-19 Test Only Needs Saliva and Yields Results in 45 Minutes: Study

 

A group of researchers has developed a new COVID-19 test. Compared to RT-PCR, the new test requires saliva samples and could produce results in 45 minutes.

The novel COVID-19 test was developed by researchers at the University of Colorado Boulder (CU Boulder), a public research university in the US. They based the test in a two-decade technology called RT-LAMP. Although it could be applied in community settings, the test is yet to receive regulatory approval. And even though its sensitivity rate was not on par the gold standard, it features a faster turnaround rate. They published their findings in the journal medRxiv.

The Gold Standard in COVID-19 Testing

According to the US Centers for Disease Control and Prevention, a federal agency, two tests are used in COVID-19: viral and antibody tests. The most accurate between the two is the viral test. The reverse transcription-polymerase chain reaction (RT-PCR) is an example and it detects the presence of SARS-CoV-2 in samples, specifically, nasal and throat swab samples. Because of its specificity and sensitivity, RT-PCR is the gold standard in COVID-19 tests and serve as a confirmatory for false negatives and false positives.

However, viral tests have a long turnaround rate of at least 24 hours. That is a wide window for a suspected individual to spread the virus if they are not quarantined. As such, there is a need for newer tests capable of augmenting the problematic turnaround rate. Antibody tests in rapid testing are developed to address the issue. Rapid testing detects the presence of SARS-CoV-2 antibodies in blood samples. It only takes several minutes to yield results but rapid testing is limited to antibodies. If a person did not produce antibodies, their antibody test is likely to be negative.

 

 

Regardless of the test used, only a licensed healthcare professional is allowed to interpret results. For example, a negative result from rapid testing may either be a true or false negative. An RT-PCR test can confirm if the individual does not have COVID-19. The same is applied to false positives. Unfortunately, the turnaround rate and the scarcity in test kits prove how challenging it is to conduct mass testing with the gold standard.

The Saliva-Based COVID-19 Testing

At CU Boulder, researchers designed a new test for COVID-19 that relies on saliva samples. It could provide results within 45 minutes – an indicator of a fast turnaround rate than RT-PCR. The technology used for the test is called reverse transcription loop-mediated isothermal amplification (RT-LAMP). Previous applications of that technology included the screening of the Zika virus from mosquitoes in select regions in South America.

"We are facing a serious testing shortage in this country right now as more people want to get tested and diagnostics labs are overwhelmed. We've developed a test that could get results to people much faster," said Nicholas Meyerson, first author of the study and postdoctoral associate in the Sawyer Lab at CU Boulder.

 

 

In the submitted paper, researchers revealed that the test is not as simple as antibody tests. But the process is not as complicated as viral tests. They conducted an experiment called contrived clinical validation to determine the accuracy rate. A total of 60 saliva samples were used in the experiment. One researcher spiked 30 samples with inactivated SARS-CoV-2. Next, that person shuffled the samples and gave them to another researcher. The second researcher tested the sample with RT-LAMP technology.

Results showed that the technology confirmed all 30 negative samples, which translated to 100% accuracy. While in 30 positive samples, the technology confirmed 29 samples. The remaining positive sample was defined as inconclusive by RT-LAMP. Despite the single error of the technology, researchers still consider its potential in curbing the pandemic.

In real-world settings, RT-LAMP will serve as a triaging tool for the prioritization of people who tested positive. Some people do not require hospital admission because they are either asymptomatic or have mild symptoms. Instead of using RT-PCR for mass testing in certain areas, RT-LAMP can be deployed first to exploit its fast turnaround rate. If any tested positive and has moderate to severe symptoms, they can be admitted to a hospital and be tested with RT-PCR. This may help both healthcare professionals and the limited supply of materials.

Roy Parker, director of BioFrontiers Institute at CU Boulder, said that mass testing is key in controlling the pandemic. And in such a context, the turnaround rate is more important than the very high sensitivity of tests. In a separate study co-authored by Parker, a computer model highlighted the difference of impact between super-sensitive tests and tests with quick turnarounds. The model pinpointed turnarounds with higher chances of identifying those with COVID-19, compared to very sensitive tests.

Since super-sensitive tests can take some time to yield results, suspected individuals may spread the virus unintentionally due to late notifications. While tests with quick turnarounds can almost immediately notify health professionals. They can recommend self-quarantine right away as they wait for confirmatory test results.

 

 

According to the World Health Organization of the United Nations, the total confirmed cases of COVID-19 worldwide were at 16,114,449, as of July 27, 2020. The total confirmed deaths due to this pandemic were at 646,641 globally. The Regions of the Americas remained with the highest confirmed cases at 8,610,134 and highest confirmed deaths at 337,439. The Western Pacific Region remained with the lowest confirmed cases at 288,151 and lowest confirmed deaths at 8,244.

In the Americas, the US had the highest confirmed cases at 4,148,011. It was followed by Brazil at 2,394,513 and Mexico at 385,036. For the number of deaths due to COVID-19, the US confirmed 145,727 deaths, Brazil confirmed 86,449 deaths, and Mexico confirmed 43,374 deaths. Aside from vaccines and treatments, new testing methods are needed to control the spread of SARS-CoV-2. These testing methods will be relevant in case the virus remains in human communities, similar to other contagious viruses like influenza and HIV.

The saliva-based test is not yet approved by the US Food and Drug Administration. Researchers confirmed paperwork submitted to the agency via Emergency Use Authorization program. If approved, the test will be commercialized and used to fight COVID-19.