- Rapid testing is appealing because receiving fast results means a person knows sooner whether they need to isolate to avoid transmitting the virus to others.
- There are three types of COVID-19 tests: Genetic (or molecular) tests, antigen tests, and antibody tests.
- An increase in rapid testing could help stop the spread of COVID-19.
As novel coronavirus vaccine trials continue, testing for SARS-CoV-2 is improving.
Specifically, there’s been a lot of development in the rapid COVID-19 tests that can detect active infections.
These new tests may help cut back on long wait times that many people face in taking COVID-19 tests. These long wait times have hampered people’s ability to determine if they need to quarantine themselves from others.
This testing is crucial, as some people don’t show symptoms of COVID-19.
Rapid testing is appealing because receiving fast results means a person knows sooner whether they need to isolate to avoid transmitting the virus to others.
There are three types of
- Genetic (or molecular) tests are most accurate and include the reverse transcription polymerase chain reaction (RT-PCR) test to pinpoint ribonucleic acid (RNA) from saliva or a nasal swab.
- Antigen tests find specific proteins on the surface of the virus.
- Antibody tests can determine if the person had the virus, but it won’t spot active infection.
Rapid RT-PCR tests
Because the SARS-CoV-2 genome is made of RNA, you need to convert it into DNA and then run a polymerase chain reaction on it.
Polymerase chain reaction (PCR) is a technique that amplifies DNA.
The enzyme that converts the RNA genome into DNA is called “reverse transcriptase,” or RT.
In order to test the virus, you have to do reverse transcriptase and then PCR, also known as a RT-PCR test, explains Dr. Geoffrey Baird, interim chair of Laboratory Medicine at the University of Washington School of Medicine. Sometimes people shorten the technique’s name to PCR, he told Healthline.
Rapid tests, also known as point-of-care tests, don’t require a lab and can be performed anywhere — including at home.
Rapid molecular or RT-PCR tests include the ID NOW by Abbott, cobas by Roche, Cue COVID-19 Test by Cue Health, Xpert Xpress by Cepheid, and Accula by Mesa Biotech.
“Currently, there are four rapid antigen tests and five rapid molecular tests
Rapid antigen tests
Rapid antigen tests look for signs that a person has antibodies for SARS-CoV-2.
These tests are much less sensitive (and accurate) than an RT-PCR test, Baird says.
These antigen tests don’t indicate whether a person is in the middle of an active infection but merely whether they had the disease in the past to the point that they developed antibodies to the disease.
Quidel’s Sofia, BD’s Veritor, Abbott’s BinaxNow, and the LumiraDx are rapid antigen tests.
Advances in rapid testing
Increasingly, medical experts are working on creating accurate and rapid tests for COVID-19 that people could take before traveling or so that they could avoid a quarantine when arriving in a new state.
A 90-minute COVID-19 test known as the CovidNudge produced by DnaNudge, a startup at Imperial College London, is already being used.
A study on the nasal swab test in
While Baird finds the CovidNudge test interesting, he says it’s not a major breakthrough. It’s easy to make a PCR gadget, and there are a lot on the market.
“Until they can make millions of these cartridges a week and get them to end users at scale at a very low price (which no vendor on earth has been able to do, ever), it will not, alone, solve our global problems,” Baird said.
Amira Roess, PhD, MPH, a professor at George Mason University in Virginia, says the CovidNudge test sounded promising. More work will need to be done to see if the high sensitivity and specificity hold true once the test is more widely used.
More COVID-19 developments
Recently, University of Illinois researcher Dr. Martin Burke has created I-COVID, a rapid RT-PCR saliva-based test that received FDA emergency use authorization.
The FDA also issued an emergency use authorization for the BinaxNOW COVID-19 Ag Card. It’s a rapid antigen test, so it’s not as accurate as a RT-PCR test.
Several tests on the horizon have received funding through the National Institutes of Health (NIH)’s
RADx gave an award to Mesa Biotech for a handheld RT-PCR test that uses a single-use cartridge and can produce results in 30 minutes. Another award went to Quidel Corporation for a 15-minute test that’s specified for nursing homes.
Some experts contend that frequent, highly accessible testing could slow the pandemic.
But it’s unclear if consumers would widely adopt at-home testing because they’d likely have to pay out-of-pocket for the tests, Karger notes.
“We also don’t yet know if this test is going to meet FDA standards for accuracy,” Karger said of the MicroGEM test. “It also is not clear whether the company can avoid supply chain issues that have plagued other manufacturers, which could potentially impede widespread distribution and availability of tests to consumers.”
Clinical trials are currently being conducted on the ICHORtec, a rapid testing system that can detect active SARS-CoV-2 infection and antibodies in non-laboratory settings in 3 minutes.
Meanwhile, a contest from XPRIZE promises to throw millions at a winner who develops an exceptional rapid COVID-19 test.
COVID-19 testing evolution
Roess believes we’ll see more tests develop that use saliva and other easily collected samples.
“Several companies are trying to come up with ways to allow patients to collect samples themselves, thereby minimizing the burden on the healthcare system as well as the risk of transmission to healthcare workers who are collecting samples,” Roess said.
On September 22, TCA/GENETWORx Labs announced its new saliva RT-PCR test, which promises results within 48 hours of testing. It’s not the first saliva test, as a few others are available.
In August, an emergency use authorization was granted by FDA for the SalivaDirect test from Yale University. SalivaDirect isn’t an at-home test and has to be performed at a lab.
Trouble with rapid tests?
Karger’s excited about new rapid and inexpensive tests but cautioned the public that the tests are generally less accurate. Most of the evidence on antigen test effectiveness was demonstrated under ideal conditions. Accuracy could diminish when the tests are performed by laypeople outside of a clinical setting.
That’s why we need to consider that deploying largely inaccurate tests could erode public health authorities, science, and medicine, Karger says.
While much attention has been paid to a potential COVID-19 vaccine, getting accurate and fast testing is key to controlling the outbreak.
Even if a COVID-19 vaccine is approved in the coming weeks, and that’s not guaranteed, it will take months before most Americans have access to that vaccine. As a result, there will still be a role for testing in the future, but the scope of that testing demand is hard to predict, Baird explained.
Stephen Kissler, PhD, a postdoctoral fellow at the Harvard T.H. Chan School of Public Health, told Healthline that the vaccine will provide one more tool to prevent virus spread, but it won’t end the pandemic.
“To manage spread, we’ll still need to use all of the interventions we have available, and rapid testing will be a key part of this,” he said. “We do still need a wider availability of rapid tests, but this is something that could feasibly happen within the next few months.”
On the horizon
As for what will improve rapid testing, Baird thinks it comes down to preventive measures and a vaccine, as they’ll both reduce the need for testing.
“There is no panacea on the horizon, meaning a test that is simultaneously nearly free, incredibly fast, and perfectly accurate,” Baird continued.
“Testing is all we can really do right now to mitigate the effect of the virus, but we cannot test our way out of this pandemic. The virus is spread because of human behavior, and changing human behavior is the only way we get out of it.”
Supply chain issues have become the most significant barrier to increasing testing volumes, Karger adds.
“In theory, we now have plenty of testing options available, but the problem is that there aren’t enough reagents or materials for labs to run these methods at full capacity.”
Developing new tests, especially ones that don’t rely on routine lab supplies, are of interest, as are “multiplex” tests that can test for more than one virus, such SARS-CoV-2, RSV, strep, and flu at the same time, Karger added.
Source: Read Full Article