Two Types of Tests, With Two Very Different Meanings

Widescale antibody testing for SARS-CoV-2 presents challenges

covid-19 testing

There’s been a lot of excitement about the potential of antibody-based blood tests, also known as serology tests, to help contain the coronavirus disease 2019 (COVID-19) pandemic, says the NIH’s 16th Director, Francis S. Collins, M.D., Ph.D.

There’s also an awareness that more research is needed to determine when—or even if—people infected with SARS-CoV-2, the novel coronavirus that causes COVID-19, produce antibodies that may protect them from re-infection, said Dr. Collins in his weekly blog, posted on May 7, 2020.

A recent study published in Nature Medicine on April 29th brings much-needed clarity to efforts to develop and implement widescale antibody testing for SARS-CoV-2. 

Antibodies are blood proteins produced by the immune system to fight foreign invaders like viruses and may help to ward off future attacks by those same invaders.

In their study of blood drawn from 285 people hospitalized with severe COVID-19, researchers in China, led by Ai-Long Huang, Chongquin Medical University, found that all had developed SARS-CoV-2 specific antibodies within two to three weeks of their first symptoms. 

Although more follow-up work is needed to determine just how protective these antibodies are and for how long, these findings suggest that the immune systems of people who survive COVID-19 have been primed to recognize SARS-CoV-2 and possibly thwart a second infection.

Specifically, the researchers determined that nearly all of the 285 patients studied produced a type of antibody called IgM, which is the first antibody that the body makes when fighting an infection. 

Though only about 40 percent produced IgM in the first week after onset of COVID-19, that number increased steadily to almost 95 percent two weeks later. Some of these patients also produced a type of antibody called IgG. 

While IgG often appears a little later after acute infection, it has the potential to confer sustained immunity.

To confirm their results, the researchers turned to another group of 69 people diagnosed with COVID-19. 

The researchers collected blood samples from each person upon admission to the hospital and every three days thereafter until discharge. 

The team found that, with the exception of one woman and her daughter, the patients produced specific antibodies against SARS-CoV-2 within 20 days of their first symptoms of COVID-19.

Meanwhile, innovative efforts are being made on the federal level to advance COVID-19 testing. 

The NIH just launched the Rapid Acceleration of Diagnostics (RADx) Initiative to support a variety of research activities aimed at improving the detection of the virus. 

As I recently highlighted on this blog, one key component of RADx is a “shark tank”-like competition to encourage science and engineering’s most inventive minds to develop rapid, easy-to-use technologies to test for the presence of SARS-CoV-2.

Sponsored Links:

On the serology testing side, the NIH’s National Cancer Institute has been checking out kits that are designed to detect antibodies to SARS-CoV-2 and have found mixed results.

In response, the Food and Drug Administration just issued its updated policy on antibody tests for COVID-19.

This guidance sets forth precise standards for laboratories and commercial manufacturers that will help to speed the availability of high-quality antibody tests, which in turn will expand the capacity for rapid and widespread testing in the United States.

Finally, it’s important to keep in mind that there are two different types of SARS-CoV-2 tests. 

Those that test for the presence of viral nucleic acid or protein is used to identify people who are acutely infected and should be immediately quarantined. 

And testing for IgM and/or IgG antibodies to the virus, if well-validated, indicates a person has previously been infected with COVID-19 and is now potentially immune. 

Two very different types of tests—two very different meanings.

There’s still a way to go with both virus and antibody testing for COVID-19. 

But as this study and others begin to piece together the complex puzzle of antibody-mediated immunity, it will be possible to learn more about the human body’s response to SARS-CoV-2 and home in on our goal of achieving safe, effective, and sustained protection against this devastating disease, concluded Dr. Collin’s weekly blog.

As of May 7, 2020, all 50 states, the District of Columbia, and certain U.S. Territories have successfully verified COVID-19 diagnostic tests and are offered by 240 testing services.

To date, 60 emergency use authorizations (EUA) have been issued for diagnostic tests under the policies set forth in the COVID-19 Policy for Diagnostic Tests for Coronavirus Disease-2019 during the Public Health Emergency Guidance.

In addition, 25 authorized tests have been added to the EUA letter of authorization for high complexity molecular-based laboratory-developed tests.

Coronavirus Today publishes diagnostic testing news.