Though experts say an antigen test is not as accurate as PCR tests, its low cost, ease of use, and widespread availability make it a boon for clinical labs performing COVID-19 testing

While COVID-19 exploded around the world, the US Food and Drug Administration (FDA) unleashed the nation’s in vitro diagnostics developers by issuing dozens of Emergency Use Authorizations for new coronavirus laboratory-developed tests (LDTs). Most of these EUAs are for Reverse Transcription-Polymerase Chain Reaction (RT-PCR) tests that detect the presence of SARS-CoV-2, the coronavirus that causes the COVID-19 illness, and for Enzyme-linked Immunosorbent Assay (ELISA) serological tests that detect antibodies present in the blood of people who have become infected with the coronavirus.

However, one LDT that received a lot of media attention was the Sofia 2 SARS Antigen FIA from Quidel (NASDAQ:QDEL), which received an EUA on May 8. The assay is designed to run on the company’s Sofia 2 Fluorescent Immunoassay Analyzer and is the first antigen test for which the FDA has issued an EUA.

As former FDA commissioner Scott Gottlieb, MD, explained on Face the Nation, “this kind of technology is a real game changer … it’s a very rapid test that could be used in a doctor’s office. Doctors now have about forty thousand of these Sofia machines already installed in their offices … you do a simple nasal swab and the test itself scans for the antigens that the virus produces.

“The test is about 85% sensitive. So, let’s say a hundred people come into a doctor’s office who have COVID-19, eighty-five of them are going to be able to be tested positive with this test very quickly. It’s a cheap test. It’ll probably be about five dollars a test and you can get a result within five minutes … you’re getting a very fast result and you can start to take action immediately.

“The company itself said that they’re going to be able to produce about two hundred thousand of these tests starting right away. But in several weeks, they’ll be able to produce up to 1.5 million a week. So, this dramatically expands our testing capacity as long as doctors are able to run these tests in their offices.”

In an interview on CBS’ Face the Nation, former FDA Commissioner Scott Gottlieb, MD (above), said, “These antigen-based tests aren’t as reliable, meaning they’re not as sensitive. So, they’re going to miss some patients who have COVID. But in the hands of a doctor who already has a high index of suspicion that the patient may have the disease … they allow you to dramatically expand testing. And they’re very cheap. They’re very easy to perform. And again, most doctors have these machines already in their offices.” (Photo copyright: US Food and Drug Administration.)

Other LDTs That Have Received EUAs

Here’s a look at other laboratory-developed tests from major manufacturers that have received emergency-use authorizations from the FDA:

Abbott Laboratories

Test: Abbott RealTime SARS-CoV-2 assay
Type: Molecular (rRT-PCR)
EUA Issued: March 18, 2020

This test is designed for use with Abbott’s m2000 RealTime system, which is installed in about 200 US medical laboratories, the company says. It can run up to 470 patient samples in 24 hours. As of a May 11 statement, the company said it had shipped more than two million tests in the US.

Test: Alinity m SARS-CoV-2 assay
Type: Molecular (rRT-PCR)
EUA Issued: May 11, 2020

This test is designed for use with Abbott’s Alinity m system, which the company describes as its “most advanced laboratory molecular instrument,” with the ability to run up to 1,080 tests in 24 hours, according to a press release.

Test: ID NOW COVID-19
Type: Molecular
Instrument: ID Now
EUA Issued: March 27, 2020

This is a rapid test designed for use with the ID Now system, a compact portable instrument for point-of-care settings such as urgent care clinics. As of May 11, Abbott said it had shipped more than 1.7 million tests in the US, and that it planned to increase manufacturing capacity to two million tests per month.

However, the test has encountered some stumbling blocks. On May 14, the FDA issued an alert stating that the ID Now COVID-19 test could produce inaccurate negative results. This came after researchers at NYU Langone Health, Northwell Health, and Cleveland Clinic reported problems with the test, according to MedTech Dive. Abbott issued a statement suggesting that the problems were due to improper sample collection and handling, however, the FDA said that Abbott had agreed to conduct post-market studies to identify the cause of the false negatives and suggest remedial actions.

Test: SARS-CoV-2 IgG assay
Type: Chemiluminescent microparticle immunoassay (CMIA) antibody test
EUA Issued: April 26, 2020

This is a qualitative test designed to detect the presence of IgG antibodies following a SARS-CoV-2 infection. The FDA authorized use of the assay on Abbott’s Architect i2000SR system in April, and then followed up with a May 11 EUA for its use on the Alinity i system. In a statement, Abbott said it planned to ship 30 million tests globally starting in May.

Cepheid

Test: Xpert Xpress SARS-CoV-2
Type: Molecular (rRT-PCR)
EUA Issued: March 21, 2020

In a March statement, the FDA touted this as the first point-of-care COVID-19 test to receive an EUA. The company estimates the detection time as approximately 45 minutes. It is designed for use with Cepheid’s GeneXpert Dx diagnostic software and GeneXpert Infinity systems, which have nearly 5,000 US installations, according to a Cepheid statement.

Hologic, Inc.

Test: Aptima SARS-CoV-2 assay
Type: Molecular (Dual Kinetic Assay)
EUA Issued: May 14, 2020

This test runs on Hologic’s Panther system, which, according to a Hologic press release, can provide results in about three hours and run more than 1,000 tests per day. The company claims that more than 1,000 Panther systems are installed in US labs, and that it expects to produce an average of one million tests per week.

This was the second Hologic test to receive and EUA. On March 16, the FDA issued an EUA for the Panther Fusion SARS-CoV-2 assay, a PCR test that runs on the Panther Fusion system.

Ortho Clinical Diagnostics

Test: VITROS Total and IgG COVID-19 Antibody Test
Type: ELISA Antibody Test
EUA Issued: April 14, 2020

Ortho’s antibody test is designed for use with its VITROS XT 7600, 3600, 5600, and ECi/ECiQ immunodiagnostic systems, which, the company says are installed in more than 1,000 US labs. The Total Reagent Pack is a qualitative test that detects the presence of all antibodies against SARS-CoV-2.

On April 24, Ortho announced it had received another FDA EUA, this one for its Anti-SARS-CoV-2 IgG test, which detects the presence of IgG antibodies. In a statement, the company said it expects to produce “several million” IgG tests per month.

Roche Diagnostics

Test: cobas SARS-CoV-2
Type: Molecular (rRT-PCR)
EUA Issued: March 12, 2020

This test is designed for use with Roche’s cobas 6800 and 8800 systems. The 6800 can process up to 384 results in an eight-hour shift, Roche says, compared with 1,056 results for the 8800 model. The company says results are available in about 3.5 hours. In a statement, Roche said it planned to ship 400,000 tests per week.

Test: Elecsys Anti-SARS-CoV-2
Type: Electrochemiluminescence immunoassay (ECLIA) Antibody Test
EUA Issued: May 2, 2020

Roche describes this as a qualitative antibody test that can be used on cobas e series immunoassay analyzers. Testing time is 18 minutes. As of May 19, the test was live at more than 20 US labs, “with plans in the next several weeks to increase to more than 200 commercial and hospital lab sites with the ability to perform millions of tests per week,” the company stated in a press release.

It’s likely the FDA will continue to issue emergency-use authorizations as the agency receives more applications from IVD manufacturers.

—Stephen Beale

Related Information:

FDA Approves First Antigen Test for Detecting the Coronavirus

Ex-FDA Chief Calls New Covid-19 Antigen Test a ‘Game-Changer’

Serology-based Tests for COVID-19

Serology Testing Free Webinar

Molecular-based Tests for COVID-19

Current Molecular and Antigen Tests with FDA EUA Status

FDA Emergency Use Authorization (EUA) Information, and List of All Current EUAs