Antibody

Quest Diagnostics

COVID-19

Quest Diagnostics

IgG antibody serology testing

Asymptomatic patients may be given an IgG antibody serology test via blood draw.

The IgG antibody test can help identify recent or prior infection to SARS-CoV-2 (which may be resolved or is still resolving), versus the molecular test which is used to help identify an active infection. The FDA has recognized that antibody tests “can indicate whether a patient has had recent or prior COVID-19 infection.”

Significant scientific advances are needed to manage the spread of COVID-19. SARS-CoV-2 IgG antibody testing is a major part of those efforts, but it is critical to confirm that the testing being used is of the highest quality and specificity.

Accuracy to provide clarity and reliability when they are needed most

At Quest, we know that the accuracy and reliability of SARS-CoV-2 (COVID-19) IgG antibody tests have been under scrutiny at a time when clarity and insights are needed most. Citing concerns about test performance and validation, the FDA has now required all antibody tests to submit applications for Emergency Use Authorizations (EUA). The IgG antibody tests currently offered by Quest were granted EUA by the FDA for public health and clinical use.

The value of antibody testing goes beyond any one individual patient.

Reliable IgG antibody tests help public health officials determine prevalence of infection in the community, particularly in under-served populations or populations with limited access to testing. Knowing the status of the population through antibody testing offers benefits globally, locally, and individually and can provide insight and guidance:

  • To help people understand whether they have been previously infected
    According to the Centers for Disease Control and Prevention (CDC), SARS-CoV-2 (COVID-19) IgG antibody tests check your blood by looking for antibodies, which may tell you if you had a past infection with the virus that causes COVID-19.1
  • On the need for subsequent molecular testing in surveillance programs
    SARS-CoV-2 IgG positive individuals may not need ongoing surveillance after recovery from their primary infection.
  • For physicians treating high-risk individuals
    Elderly individuals and those patients with COPD or cardiovascular risks may have higher risk of severe clinical outcomes from SARS-CoV-2 (COVID-19).2

Physicians and public health experts have identified potential clinical applications for SARS-CoV-2 (COVID-19) IgG antibody testing, including:

  • Clinical assessment of individuals who present 9-14 days after illness onset
    Antibody testing may be used in conjunction with molecular testing per CDC guidelines.
  • Treating high-risk individuals
    Elderly individuals and those patients with COPD or cardiovascular risks may be at higher risk of severe clinical outcomes from COVID-19.2
  • Blood donors
    Individuals whose blood contains antibodies may be eligible to serve as blood donors of convalescent plasma, which may provide an avenue for possible treatment for those who are seriously ill from COVID-19.
  • Part of return to work and society programs
    For example, antibody testing may be part of these comprehensive protocols created by Quest Diagnostics based on CDC guidelines.

It is not yet known how long antibodies persist following infection, if the presence of antibodies affords immunity, how long such immunity might last, and whether the presence of antibodies provides full protection from reinfection. Individuals may have detectable virus for several weeks following seroconversion.

IgG antibody testing must be ordered by a physician. Patients may make an appointment at a Quest patient service center for this test.

References

1Centers for Disease Control and Prevention (CDC). Test for past infection (antibody test). Updated June 30, 2020. https://www.cdc.gov/coronavirus/2019-ncov/testing/serology-overview.html. Accessed July 6, 2020.

2Centers for Disease Control and Prevention (CDC). People of any age with underlying medical conditions. Updated June 25, 2020. https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-with-medical-conditions.html. Accessed July 6, 2020.

 

Turnaround time for the IgG antibody serology COVID-19 test is typically 1-2 days from the time the specimen is received in our laboratory, but can vary due to high demand.

Quest continues to scale up testing capacity on the serology platform by expanding testing across its network of laboratories and adding other IVD testing platforms.

Current Turnaround

1-2 days
from specimen pickup

IgG antibody testing must be ordered by a physician. Healthcare professionals can now order COVID-19 antibody serology testing using test code 39504.

It is reasonable to conduct an IgG antibody test after 14 days of being symptom-free because most people will develop an IgG response in that timeframe. Further studies may further define and/or shorten the testing window.

The SARS-CoV-2 antibody test has not been validated for purposes of diagnosis of infection or disease (COVID-19) and cannot be used to rule in or rule out infection of COVID-19. Quest offers the molecular test (test code 39448) for diagnosing an active COVID-19 infection.

The IgG antibody test can help identify recent or prior infection to SARS-CoV-2 (which may be resolved or is still resolving), versus the molecular test which is used to help identify an active infection.

The FDA has recognized that antibody tests “can indicate whether a patient has had recent or prior COVID-19 infection.”

Video update on IgG antibody serology testing

Jay G. Wohlgemuth, M.D.
Senior Vice President, R&D, Medical and Chief Medical Officer

Quest Diagnostics patient service centers are not accepting patients with suspected or confirmed COVID-19 and are not collecting respiratory specimens for COVID-19 molecular testing.

Blood specimens for SARS-CoV-2 antibody testing can be collected by a hospital or health system or in any healthcare setting where a licensed phlebotomist can draw blood. Quest will be collecting serology specimens at patient service centers (PSCs) by appointment across the country, but not during the hours designated for the Peace of Mind program reserved for patients at greatest risk for COVID-19.

The personnel at our PSCs are trained in collecting a range of specimens, including blood and urine, for various medical health conditions, but not respiratory specimens for COVID-19 or other respiratory illnesses such as influenza.

Quest recommends individuals who suspect they have COVID-19 contact their healthcare provider directly about COVID-19 testing. Quest laboratories are accepting and performing testing on COVID-19 specimens submitted by healthcare providers across the United States.

What is the test name and test code?

The test name in the Quest Test Directory for all IVD platforms for IgG antibody testing is SARS-CoV-2 Serology (COVID-19) Antibody (IgG), Immunoassay. The test code is 39504.

What is the SARS-CoV-2 serology test from Quest?

The SARS-CoV-2 Serology (COVID-19) Antibody (IgG), Immunoassay test is a qualitative test to detect IgG antibodies to the SARS-CoV-2 virus in an individual's blood. The test code 39504 includes testing for the IgG antibody only. The IgG antibody tests currently offered by Quest Diagnostics were granted Emergency Use Authorizations (EUA) by the FDA for public health and clinical use—Abbott Architect, Ortho Clinical Diagnostics, and EuroImmun. These tests have specificity values of 99.6% to 100% which minimizes false positives, and sensitivity values of approximately 90% to 100%.

Where can I find test specific information?

All test specific information can be found in the test directory—test code 39504.

Are Quest's IgG antibody test offerings for SARS-CoV-2 accurate?

The IgG antibody test is a specific test used to detect IgG antibodies to the SARS-CoV-2 virus in your blood. The IgG antibody tests currently offered by Quest Diagnostics were granted Emergency Use Authorizations (EUA) by the FDA for public health and clinical use—Abbott Architect, Ortho Clinical Diagnostics, and EuroImmun. These tests have specificity values of 99.6% to 100% which minimizes false positives, and sensitivity values of approximately 90% to 100%.

The IgG antibody test can help identify recent or prior infection to SARS-CoV-2 (which may be resolved or is still resolving), versus the molecular test which is used to help identify an active infection. The FDA has recognized that antibody tests “can indicate whether a patient has had recent or prior COVID-19 infection.” Citing concerns about test performance and validation, the FDA has now required all antibody tests to submit applications for EUA.

As a result of this process, the agency has identified numerous antibody test offerings that should not be used or distributed. In addition, the FDA has revoked an EUA where there were performance concerns. In addition to the robust validation performed by the manufacturers on each of the platforms, Quest verifies the performance characteristics of the assays using stringent acceptability criteria for precision, reproducibility, accuracy, method comparison, cross-reactivity, and clinical performance before starting patient testing.

Why is antibody testing important?

COVID-19 is a new infectious disease. Scientists are working to understand many things about it, such as how it spreads from person to person, why it affects people differently, how an individual’s immune system responds to the virus, and if people can be infected more than once. To expand our knowledge and manage the spread of this virus, we need significant scientific advances—and antibody testing is a major part of those efforts, especially when used in conjunction with COVID-19 molecular testing. Antibody testing plays a critical role in the fight against COVID-19 by helping providers identify individuals who may have been infected by SARS-CoV-2.

Knowing the status of the population through antibody testing offers benefits globally, locally, and individually.

  • Helps public health officials determine prevalence of infection in the community.
  • Provides guidance on the need for subsequent molecular testing for SARS-CoV-2 in surveillance programs (eg, IgG positive individuals may not need ongoing surveillance after recovery from their primary infection).
  • Provides insight to help people understand whether they have been previously infected. Individuals who have been infected and recovered from SARS-CoV-2 may have a decreased risk of reinfection.
  • The use of antibody testing may be particularly valuable to physicians treating individuals who are vulnerable and at higher risk of severe clinical outcomes from COVID-19 (eg, elderly individuals and those patients with COPD or cardiovascular risks).
  • May be used in conjunction with other testing and a comprehensive protocol in return to work and society programs.
  • Individuals whose blood contains antibodies may be eligible to serve as blood donors of convalescent plasma, which may provide an avenue for possible treatment for those who are seriously ill from COVID-19.

When should an IgG serology test be performed?

It is reasonable to conduct an IgG antibody test after 14 days of being symptom free because most people will develop an IgG response in that timeframe. Further studies may further define and/or shorten the testing window.

What is the difference between molecular PCR testing and antibody testing for COVID-19?

The IgG antibody test can help identify recent or prior infection to SARS-CoV-2 (which may be resolved or is still resolving), versus the molecular test which is used to help identify an active infection.

Has there been public guidance issued to healthcare providers on the clinical use of SARS-CoV-2 serology testing?

Yes. In a letter issued on April 17, 2020, the U.S. Food and Drug Administration (FDA) recommended that healthcare providers continue to use serological tests intended to detect antibodies to SARS-CoV-2 to help identify people who may have been exposed to the SARS-CoV-2 virus or have recovered from the COVID-19 infection. In its guidance, the FDA referenced that experience with other viruses suggests that individuals whose blood contains IgG antibodies associated with SARS-CoV-2 infection—provided they are recovered and not currently infected with the virus—may be able to resume work and other daily activities in society. They may also be eligible to serve as potential donors of convalescent plasma to aid in the treatment of those infected with COVID-19.

Who should be tested using the COVID-19 serology test?

The SARS-CoV-2 antibody test has not been validated for purposes of diagnosis of infection or disease (COVID-19) and cannot be used to rule in or rule out infection of COVID-19. Quest offers the molecular test (test code 39448) for diagnosing an active COVID-19 infection.

The IgG antibody test can help identify recent or prior infection to SARS-CoV-2 (which may be resolved or is still resolving), versus the molecular test which is used to help identify an active infection. The FDA has recognized that antibody tests “can indicate whether a patient has had recent or prior COVID-19 infection.”

Where can the SARS-CoV-2 serology specimens be collected?

Blood specimens for SARS-CoV-2 antibody testing can be collected by a hospital or health system or in any healthcare setting where a licensed phlebotomist can draw blood. Quest will be collecting serology specimens at patient service centers (PSCs) by appointment across the country, but not during the hours designated for the Peace of Mind program for those patients at greatest risk for COVID-19.

How will the Quest Diagnostics SARS-CoV-2 antibody test results be reported?

There will be 3 results: Positive, Equivocal, and Negative. Each result will carry a comment consistent with the FDA guidelines. As the IgG test is used to detect prior exposure to the virus, and not to diagnose active infection, this test is not a Priority test and providers will not be contacted to discuss results. Providers should obtain results via standard processes. Patients will be notified through the online MyQuest portal if they signed up for it.

What type of specimen is used for the SARS-CoV-2 serology test?

A serum sample obtained by taking a blood sample.

Should the SARS-CoV-2 antibody test be submitted on its own requisition?

SARS-CoV-2 antibody test (test code 39504) does not need to be on its own requisition.

What is Quest's capacity for the serology test?

Quest is continuing to scale up testing capacity on the serology platform by expanding the test across its network of laboratories and adding other testing platforms.

How should SARS-CoV-2 antibody tests be interpreted?

A positive IgG antibody test result suggests recent or prior infection with SARS-CoV-2. It usually takes at least 10 days after symptom onset for IgG detectable levels to be reached. Patients tested prior to this time may be negative for SARS-CoV-2 IgG antibodies. An IgG positive result may suggest an immune response to a primary infection with SARS-CoV-2, but the relationship between IgG positivity and immunity to SARS-CoV-2 has not yet been firmly established. Antibody tests have not been shown to definitively diagnose or exclude SARS-CoV-2 infection.

Presence of SARS-CoV-2 antibodies has been demonstrated in patients with undetectable viral RNA. Therefore, testing asymptomatic healthcare workers or patients with negative molecular diagnostic test results with antibody tests may add value in determining whether they have been exposed to SARS-CoV-2 or not.

What are the limitations of antibody testing?

It is critical to confirm that the antibody testing being used is of highest quality and specificity. Antibody testing cannot stand on its own as the primary indicator of health status in response to COVID-19, but can be a valuable tool as part of a comprehensive response to the global pandemic.

It is not yet known how long antibodies persist following infection, if the presence of antibodies affords immunity, how long such immunity might last, and whether the presence of antibodies provides full protection from reinfection. Individuals may have detectable virus for several weeks following seroconversion. Per EEOC Guidelines, employers should not require antibody testing before allowing employees to re-enter the workplace.

  • EuroImmun website: https://www.coronavirus-diagnostics.com/faq.html Accessed April 13, 2020.
  • FDA. Fact Sheet Serological testing for antibodies to SARS CoV-2 infection. Published April 17, 2020. Accessed April 18, 2020. https://www.fda.gov/media/137111/download
  • Nebehay S. WHO is investigating reports of recovered COVID patients testing positive again. Reuters. Published April 11, 2020. https://www.reuters.com/article/us-health-coronavirus-who/who-says-looking-into-reports-of-some-covid-patients-testing-positive-again-idUSKCN21T0F1?il=0idUSKCN21T0F1?il=0
  • United States Food and Drug Administration FAQs on Diagnostics Testing for SARS CoV-2. Accessed April 12, 2020. https://www.fda.gov/medical-devices/emergency-situations-medical-devices/faqs-diagnostic-testing-sars-cov-2
  • Wu L-P, Wang N-C, Chang Y-H, Tian X-Y, Na D-Y, Zhang L-Y, et al. Duration of antibody responses after severe acute respiratory syndrome. Emerg Infect Dis. 2007;13(10):1562-1564.
  • Zhao J, et al. Antibody responses to SARS CoV-2 in patients with novel coronavirus disease 19. Oxford University Press. Accessed April 12, 2020. https://www.medrxiv.org/content/10.1101/2020.03.02.20030189v1

Important information about COVID-19 antibody testing

The test is designed to detect antibodies to SARS-CoV-2, the virus that causes COVID-19. Antibodies are proteins that the body produces in response to infections. The antibodies can be produced even if a person has few or no symptoms during the infection.

It generally takes some time after infection for antibodies to be produced and become detectable in blood (sometimes up to 3 weeks). It is important to remember that we do not yet know whether having antibodies to SARS-CoV-2 will prevent against getting the infection again or if you are totally free of the virus. Antibodies are generally detectable in the blood for a period of time after a person has recovered from the infection and after the virus that caused the infection is no longer detectable by laboratory methods.

Sometimes the antibodies developed in response to an infection protect us from getting that same infection again. But, it is important to know that we do not yet know whether this is true for COVID-19. Even if you have recovered and have antibodies, there is a chance that you still have the virus and you can infect others, it is still critical to keep taking measures to avoid getting infected again and/or spreading infection.

The antibody test is not meant for detecting an active infection. The swab test (sometimes also known as a molecular, RNA or PCR test) should be used to test for active infection.

A negative antibody test result means that antibodies were not detected in your blood sample. This can have several possible meanings. It could mean that:

  • You have not been infected with SARS-CoV-2, or
  • You have been infected with SARS-CoV-2, but your antibodies have not reached a sufficient level for the test to be able to detect them, or
  • You have been infected with SARS-CoV-2, but there has not been enough time for antibodies to develop (it can take up to one to three weeks to develop antibodies after someone is infected, sometimes longer).

A positive antibody test result means that antibodies were detected in your blood sample. This can have a couple of possible meanings. It could mean that:

  • You have been infected with SARS-CoV-2 at some point in the past, or
  • Uncommonly, you may have developed antibodies from an earlier infection with a different virus related to SARS-CoV-2 and the laboratory test cannot distinguish between these other virus antibodies and those antibodies generated in response to SARS-CoV-2.

COVID-19 testing statements

  • The antibody tests and the molecular tests (together “All tests”) have not been FDA cleared or approved;
  • All tests have been authorized by FDA under EUAs for use by authorized laboratories;
  • The antibody tests have been authorized only for the detection of IgG antibodies against SARS-CoV-2, not for any other viruses or pathogens;
  • The molecular tests have been authorized only for the detection of nucleic acid from SARS-CoV-2, not for any other viruses, pathogens; and,
  • All tests are only authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Act, 21 U.S.C. § 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner.