COVID-19 Antibody Testing

COVID-19 Overview

Coronaviruses are a family of viruses ranging from the common cold to severe acute respiratory syndrome (SARS).  While coronaviruses have been in existence for many years, the most recent virus to emerge, COVID-19, is what most people think of when they hear the term.  The COVID-19 virus, originating in Wuhan, China in December of 2019, is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).  Symptoms typically appear within two to 14 days after initial exposure, can vary in both severity and duration, and are characterized by fever, cough, tiredness, aches, and breathing difficulties.  Some patients show no symptoms at all (asymptomatic) and may never know they have the virus unless diagnosed.  As of this writing, COVID-19 has infected roughly 3,000,000 worldwide and resulted in more than 200,000 deaths.  In the United States alone, there have been nearly 1,000,000 COVID-19 cases and in excess of 55,000 fatalities.

What are Antibodies and What Do They Do?

Specialized, Y-shaped proteins created by our immune systems, our bodies manufacture antibodies, also called immunoglobulins, as a response to an infection.  When an infection (antigen) enters the body, the immune system begins creating antibodies.  Acting as a scout of sorts, antibodies identify the antigen, sticks to it, and signals for the body to destroy the antigen.  Antibodies are particular in that they are made for only one specific antigen and have special receptors that only bind to that specific antigen.

When an antigen enters the body, it is met by a group of cells called B cells.  The responsibility of the B cells are to create antibodies that match the antigen.  After the antibodies are created, they stick to the antigen and signal to T cells to begin attacking.  Once the antigen is destroyed, phagocytes, large cells that consume foreign matter, eat the remainder of the infection.

By recognizing bacteria, viruses, and infected cells, antibodies not only help our body fight against infection but could potentially provide a level of immunity against future infection from the same antigen.  Antibodies are also beneficial in that they can be used to diagnose diseases and create treatments.  For example, if antibodies associated with a specific disease are not detected in a person’s blood, it can signal that they are either not currently infected or that any infection occurred so long ago that the specific antibodies have naturally decayed.

About the Quest Diagnostics Antibody Testing

The antibody test offered through Quest Diagnostics begins by drawing blood serum specimens from a patient (serology testing) that was either positively diagnosed with COVID-19 or suspects they may have previously been infected with the virus.  The specimens are then tested to see if antibodies are detected.

The newly available antibody test offered by Quest Diagnostics, uses tests that were created for high-throughput laboratory environments based on those from Abbott and EUROIMMUN.  Both the EUROIMMUN and Abbott tests are marketed under the Food and Drug Administration’s (FDA) Policy for Diagnostic Tests for Coronavirus Disease 2019.  As of April 28th, 2020 the FDA has approved the Abbott antibody testing through the (EUA) Emergency Utilization Act.  EUROIMMUN is currently seeking an Emergency Use Authorization (EUA) through the FDA and has received the CE marking. This is a certification mark that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area (EEA).  Emergency Use Authorization allows for unapproved medical products to be used in emergency situations to treat, diagnose, or prevent serious or life-threatening diseases when no adequate or approved alternatives are available.  Independent validation studies performed by Quest Diagnostics on both tests, indicate they are able to detect the antibody immunoglobulin class G (IgG) which generally develops within 14 days of the onset of symptoms at over 95% specificity and sensitivity.

While the test results should be interpreted along with other factors, such as history and symptoms, the results indicate that antibodies are present.  Though antibodies may be detected, clinical trials have not yet established whether a patient is immune from future infection.  As such, antibody testing alone is limited in immediate value for patients diagnosed or suspected to have been infected with COVID-19.

"As the FDA has indicated, antibody testing has the potential to help healthcare professionals identify people who have been exposed to COVID-19 and who have developed an immune response," said Jay G. Wohlgemuth, M.D., Senior Vice President and Chief Medical Officer for Quest Diagnostics. "In addition, FDA has indicated that antibody testing can help identify those who could contribute a part of their blood, called convalescent plasma, which may provide an avenue for possible treatment for those who are seriously ill from the coronavirus."

When the new antibody test was first announced on April 21, 2020, Quest had the capability to conduct approximately 70,000 per day. Since FDA approval of the Abbott antibody testing kits, Abbott has begun to ship out millions of kits to hospitals and medical facilities. Depending on demand for the antibody tests, Quest anticipates being able to report results to our facility within one to two days after collecting the blood specimens.

Who Can Get Antibody Testing?

Based on the Centers for Disease Control and Prevention (CDC) safety and health guidelines, COVID-19 antibody testing is only available for patients that are asymptomatic, have not had symptoms for a minimum of 10 days, do not have a fever, have been given a requisition for a test from a healthcare provider, and are wearing a face mask when blood is drawn.  Patients that want to undergo COVID-19 antibody testing, should schedule an appointment with our clinic ahead of time.  Any patient that has a current diagnosis of COVID-19 should stay home and follow the current quarantine guidelines. Those who suspected they have a COVID-19 infection, should call to schedule a medical evaluation for Telehealth or in clinic if necessary. The antibody test is for those without any symptoms, if symptoms are present then nasal molecular testing is advised.