IVD Companies and medical laboratories are developing serological survey testing that will enable them to determine how widespread COVID-19 has become

While medical laboratories gear up for testing to detect SARS-CoV-2—the novel coronavirus that causes the COVID-19 illness—efforts also are underway for expanded use of serological tests that can detect whether an individual’s immune systems has developed antibodies against the SARS-CoV-2 virus, as well as serological surveys that epidemiologists will use to determine the extent of the infection in whole populations.

It can take up to eight days after onset of symptoms for a person’s immune system to develop antibodies, so serological tests are not designed for diagnosing recent or active infections, stated a Mayo Clinic news story. However, Reuters reported that the availability of serological tests is “a potential game changer” because they could identify people who are immune even if they had no symptoms or only mild symptoms.

“Ultimately, this might help us figure out who can get the country back to normal,” Florian Krammer, PhD, told Reuters. Krammer’s lab at the Icahn School of Medicine at Mount Sinai in New York City has developed a serological test. “People who are immune could be the first people to go back to normal life and start everything up again,” he said.

However, some experts advise that the presence of antibodies is not necessarily a “get out of jail free” card when it comes to the coronavirus. “Infectious disease experts say immunity against COVID-19 may last for several months and perhaps a year or more based on their studies of other coronaviruses, including Severe Acute Respiratory Syndrome (SARS), which emerged in 2003,” reported Reuters. “But [the experts] caution that there is no way to know precisely how long immunity would last with COVID-19, and it may vary person to person.”

Additionally, it is also “uncertain whether antibodies would be sufficient protection if a person were to be re-exposed to the virus in very large amounts,” such as in an emergency room or ICU, Reuters reported.

Serological Survey Studies Get Underway Worldwide

Aside from detecting potential immunity, the World Health Organization (WHO) says serological tests could be useful for widespread disease surveillance and epidemiological research.

In the US, the Vitalant Research Institute is leading several large serological survey or “serosurvey” studies in which regional blood centers save samples of donated blood for antibody testing, Science reported.

Science also reported on a similar WHO initiative in which six countries will pool data from their own antibody studies. And in the Netherlands, blood banks have begun screening thousands of blood donations for presence of antibodies, Wired reported.

FDA Emergency Use Authorization

On March 16, the federal Food and Drug Administration (FDA) announced that it would allow commercial development and distribution of serological tests that “identify antibodies (e.g., IgM, IgG) to SARS-CoV-2 from clinical specimens” without an Emergency Use Authorization (EUA). The agency noted that these tests are “less complex than molecular tests” used to detect active infections, and that the policy change is limited to such testing in medical laboratories or by healthcare workers at the point-of-care. “This policy does not apply to at home testing,” the FDA reiterated.

“Serological tests can play a critical role in the fight against COVID-19 by helping healthcare professionals to identify individuals who have overcome an infection in the past and have developed an immune response,” said FDA Commissioner Stephen M. Hahn, MD (above with President Trump during a Coronavirus Task Force press briefing), in an April 7 press statement. “In the future, this may potentially be used to help determine—together with other clinical data—that such individuals are no longer susceptible to infection and can return to work. In addition, these test results can aid in determining who may donate a part of their blood called convalescent plasma, which may serve as a possible treatment for those who are seriously ill from COVID-19.” (Photo copyright: CNBC.)

FDA Issues First EUA for Rapid Diagnostic Test

Cellex Inc., based in Research Triangle Park, N.C., received the first EUA for its qSARS-CoV-2 serological test on April 1. As with other rapid diagnostic tests (RDTs) under development, the qSARS-CoV-2 test detects the presence of immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in human blood. The biotechnology company’s RDT can be used to test serum, plasma, or whole-blood specimens, stated Cellex, and can produce results in 15 to 20 minutes.

The FDA has authorized use of the antibody test only by laboratories certified under CLIA to perform moderate and high complexity tests. Cellex has set up a COVID-19 website with information about the qSARS-CoV-2 test for clinical laboratories, patients, and healthcare providers.

Other Serological Tests Under Development

Mayo Clinic Laboratories announced on April 13 that it is ramping up availability of an internally-developed serological test. “Initial capacity will be 8,000 tests per day performed at laboratory locations across Mayo Clinic,” stated the announcement. “Testing will be performed 24 hours a day, and Mayo Clinic Laboratories is working to ensure turnaround time is as close as possible to 24 hours after receipt of the sample.”

Emory University in Atlanta announced on April 13 that it will begin deploying its own internally developed antibody test. Initially, testing will be limited to 300 people per day, comprised of Emory Healthcare patients, providers, and staff members. Eventually, testing will be “expanded significantly,” said Emory, with a goal of 5,000 tests per day by mid-June.

The Center for Health Security at the Johns Hopkins Bloomberg School of Public Health lists dozens of other serologic tests that are under development, approved for use in other countries, or approved for research or surveillance purposes. Most are rapid diagnostic tests, but some developers are working on enzyme-linked immunosorbent assays (ELISA).

RDTs are typically qualitative, meaning they produce a positive or negative result, stated the Center for Health Security. An ELISA test “can be qualitative or quantitative,” noted the Center, but it can take one to five hours to produce results.

A third type of serological test—the neutralization assay—involves infecting a patient’s blood with live coronavirus to determine if antibodies exist that can inhibit growth of the virus. The test takes three to five days in a level 3 biosafety laboratory to produce results. The Straits Times reported on one laboratory in Singapore that developed a neutralization assay to trace the source of COVID-19 infections that originated in Wuhan, China.

Serological testing is another important tool clinical laboratories and epidemiologists can use to fight and ultimately defeat the COVID-19 pandemic and is worth watching.

—Stephen Beale

Related Information:

Coronavirus (COVID-19) Update: Serological Tests

Policy for Diagnostic Tests for Coronavirus Disease-2019 during the Public Health Emergency

Advice on the Use of Point-of-Care Immunodiagnostic Tests for COVID-19

Serology-based Tests for COVID-19

FDA Officially Authorizes Its First Serological Antibody Blood Test for COVID-19

Cellex Cleared to Market Antibody Test for COVID-19

What Are Antibody Tests and What Do They Mean for the Coronavirus Pandemic?

Cellex qSARS-CoV-2 IgG/IgM Rapid Test

IgG/IgM Rapid Test Approved by FDA for EUA Use

EDI Novel Coronavirus COVID-19 ELISA Kits

Mayo Clinic Laboratories Launches Serology Testing In Support of COVID-19 Response