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COVID-19 antibody testing can play an important role in identifying people who have recovered from the SARS-CoV-2 virus and who have high levels of antibodies in their blood that could potentially help other critically ill COVID-19 patients. The presence of antibodies may also suggest immunity from future infection.

As many dermatology practices begin to contemplate reopening their doors, COVID-19 and SARS-CoV-2 antibody testing of staff and patients is being considered as a way to help mitigate expsoure to and the spread of COVID-19.

But what do tests results really mean, and can they play a role in screening patients and staff for immunity before reopening practices?

Testing for Active Infection Remains Most Important

The most important test at this point in time is a nasal swab for active infection, says Len Horovitz, MD, a pulmonologist in New York City.

“Dermatologists, gastroenterologists, plastic surgeons and any other doctor who wants to do elective procedures should do polymerise chain reaction (PCR) swabs of patients so they don’t bring COVID-19 into the office.”

Antibody testing alone may miss many patients with active COVID-19. “You don’t make antibody until two weeks into the illness,” Dr. Horovitz explains.

False negatives are not overly concerning, but false-positive results in antibody testing can make a person think they are immune when they are not.

“A person with true antibodies to COVID-19 can go out to society with a kind of passport of immunity and they will be the open uppers in the short term.” Reinfection has not been documented, but antibodies may not confer permanent immunity, he notes.

“Of course we would like everyone to have a PCR nasal swab for COVID and antibody testing to get a sense of the prevalence of the disease in population so we can know how close we are to achieving herd immunity,” he says.

FDA Increases Oversight

The FDA recently tightened requirements for antibody tests, as they had allowed diagnostic manufacturers to sell antibody tests without undergoing agency review. Multiple tests hit the market that were flawed or did not meet their standards. Now FDA requires manufacturers to apply for emergency use authorization within 10 days of releasing an antibody test. FDA has provided specific performance threshold recommendations for specificity and sensitivity for all serology test developers.

At press time, the FDA had given its nod to 13 COVID 19 antibody tests under their Emergency Use Authorization (EUA) authority. These are listed on page 40.

Tests Perform Differently

All tests may not be created equal, despite receiving the green light from the FDA, according to a study in Clinical Chemistry. Researchers compared the performance of the Abbott SARS-CoV-2 IgG and the Euroimmun Anti-SARS-CoV-2 ELISA (IgG).

With these tests, the researchers analyzed 103 specimens from patients with COVID-19 infections diagnosed using standard molecular testing and 153 specimens from healthy individuals. The researchers found that Abbott’s test had a specificity of 99.4 percent and a sensitivity of 93.8 percent at ≥14 days after symptom onset, while Euroimmun’s test had a specificity of 94.8 percent and a sensitivity of 85.4 percent at ≥14 days after symptom onset.

Overall, the Abbott test’s high sensitivity and specificity mean that it produces fewer inaccurate results than Euroimmun’s test, the study showed. However, it’s worth noting that the 93.8 percent sensitivity that the researchers found for this test is actually lower than the 100 percent sensitivity that the company states its test exhibits. A possible explanation for this discrepancy is that the test subjects Abbott used were likely patients who had fully recovered from COVID-19, while Clinical Chemistry study included hospitalized patients, the researchers point out.

FDA-Cleared SARS-CoV-2 Antibody Tests

At press time, FDA had approved 13 COVID 19 antibody tests:

Cellex Inc. qSARS-CoV-2 IgG/IgM Rapid Test

The Cellex qSARS-CoV-2 IgG/IgM Rapid Test is a lateral flow chromatographic immunoassay which can detect antibodies against the SARS-CoV-2 virus.

Ortho Clinical Diagnostics, Inc. Vitros Anti-SARS-CoV-2 IgG Test

This test measures human SARS-CoV-2 IgG antibodies, that are generated as part of the adaptive immune response to the virus and is to be performed only using human serum.

Ortho Clinical Diagnostics, Inc. Anti-SARS-CoV-2 Total Reagent Pack VITROS Immunodiagnostic Products

The VITROS Immunodiagnostic Products Anti-SARSCoV-2 Total Reagent Pack test is authorized for the detection of total antibody (including IgG, IgA and IgM) to SARS-CoV-2 in human serum and plasma (K2 EDTA). Ortho Clinical Diagnostics is working with Quest Diagnostics to expand COVID-19 antibody testing to more than 20 Quest laboratories across the US.

Chembio Diagnostic System, Inc DPP COVID-19 IgM/IgG System

These results can be obtained within 15 minutes from a simple finger stick utilizing Chembio’s MicroReader 1 and MicroReader 2 analyzers which are produced by Chembio Germany.

“The results and data from our DPP COVID-19 test can help improve clinical outcomes through the management of individual patients by enabling clinicians to understand the likelihood of past and present infection and to manage populations as a whole as a surveillance test,” states Richard Eberly, Chief Executive Officer of Chembio, in a news release. “Our measured approach has positioned us to offer a viable and sustainable long-term solution for clinicians. We expect to begin shipping product in April 2020, and we will continue to work with our partner LumiraDx to provide DPP COVID-19 tests with the ability to scale based upon market demand.”

Mount Sinai Laboratory COVID-19 ELISA IgG Antibody Test Serology IgG

“Our test can pick up the body’s response to infection, in some cases as early as three days post-symptom onset, and is highly specific and sensitive,” says Florian Krammer, PhD, Professor of Microbiology at the Icahn School of Medicine at Mount Sinai, who began working on the serologic test in January 2020 “We have shared the toolkit needed to set up the test with more than 200 research laboratories worldwide to help mitigate this global crisis.”

Autobio Diagnostics Co. Ltd. Anti-SARS-CoV-2 Rapid Test

By using a patient’s serum or plasma specimen, the Anti-SARS-CoV-2 Rapid Test offers a turnaround time of only 15 minutes. This simple-to-use test requires no equipment or special expertise or training to implement.

DiaSorin Inc. LIAISON SARS-CoV-2 S1/S2 IgG

The kit provides a sample-to-answer test for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, directly from nasopharyngeal swab specimens. The Simplexa COVID-19 Direct kit is designed for use on the LIAISON® MDX and can be utilized by hospital laboratories without the need to send the sample out, allowing for timely testing and results. The kit contains an all-in-one reagent mix, which is ready to use.

Abbott Laboratories Inc. Alinity i system SARS-CoV-2 IgG assay/ Abbott Architect SARS-CoV-2 IgG

Abbot planned to ship nearly 30 million antibody tests globally in May across its ARCHITECT and Alinity I platforms and will have capacity for 60 million tests in June.

Bio-Rad Laboratories, Inc. Platelia SARS-CoV-2 Total Ab assay

The Platelia SARS-CoV-2 Total Ab assay is a qualitative in vitro diagnostic test, in a one-step antigen capture format, for the detection of Total antibodies to SARS‐CoV-2 in human serum and plasma (EDTA) specimens, according to the FDA

Wadsworth Center, New York State Department of Health New York SARS-CoV Microsphere Immunoassay for Antibody Detection

Wadsworth’s New York SARS-CoV Microsphere Immunoassay for Antibody Detection is designed to detect human immunoglobulin G, immunoglobulin M, and immunoglobulin A antibodies against SARs-CoV-2 in serum. It runs on the Luminex FlexMap dual laser cytometer and is only authorized for use by Wadsworth.

Roche Diagnostics Elecsys Anti-SARS-CoV-2

The Elecsys Anti-SARS-CoV-2 immunoassay is authorized for on the detection of antibodies to SARSCoV-2 in human serum or plasma.

Euroimmun Anti-SARS-CoV-2 ELISA (IgG).

The Euroimmun Anti-SARS-CoV-2 ELISA (IgG). is authorized for the detection of IgG antibodies to SARS-CoV-2 in human serum and plasma (K+- EDTA, Li+-heparin, Na+-citrate)

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