Antibody

Quest Diagnostics

COVID-19

Quest Diagnostics

IgG antibody serology testing to indicate SARS-CoV-2 exposure

Asymptomatic patients may be given an IgG antibody serology test via blood draw. The IgG antibody serology test is one tool that may help identify people who may have been previously exposed to or overcome SARS-CoV-2. It may indicate prior infection which may be resolved, as well as potential protection against re-infection (“protective immunity”).

Quest is collecting COVID-19 IgG antibody specimens and performing testing nationwide.

Quest’s IgG antibody test may be especially useful for people without symptoms, including healthcare workers. An IgG positive result may suggest an immune response to a primary infection with SARS-CoV-2. While the role of antibodies in preventing COVID-19 disease has yet to be established, antibody testing for other respiratory illnesses (SARS, flu) provides insight into immunity to future diseases.

Knowing IgG status helps give individuals and their healthcare providers insight for a more informed decision about returning to work and activity.

IgG antibody testing must be ordered by a physician. Patients may make an appointment at a Quest patient service center for this test. For the safety of our patients and employees, antibody serology testing appointments will only be scheduled outside of the established hours for the Peace of Mind program reserved for patients at higher risk of contracting COVID-19.

Note: The IgG antibody serology test is not intended for diagnosis of active COVID-19 infection. If the patient has symptoms or you have reason to suspect active infection, the molecular PCR testing (test code 39448) is available to be ordered by an authorized healthcare provider for diagnosis. Molecular PCR specimen collection does not take place at Quest patient service centers.

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

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

The SARS-CoV-2 (COVID19) antibodies, Immunoassay test is a qualitative (IgG) immunoglobulin test to detect antibodies to the SARS-CoV-2 virus in the blood. The test code 39504 includes testing for the IgG antibody only. It provides insight into whether an individual has previously been exposed to the SARS-CoV-2 virus and may have some level of immunity.

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.

IgG antibody testing may be performed on healthcare workers and patients who currently have few to no symptoms but have been exposed to SARS-CoV-2 in the past.

If a serology test delivers a positive result for the IgG antibody, that means the individual was previously exposed to SARS-CoV-2 and may have developed some level of immunity to the virus.

Note: 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.

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 and will provide insight into whether an individual has previously been exposed to the SARS-CoV-2 virus and may indicate prior infection which may be resolved, and/or protection against re-infection (“protective immunity”).

While the role of antibodies in preventing COVID-19 disease has yet to be established, antibody testing for other respiratory illnesses (SARS, flu) provides insight into immunity to future diseases.

Where can I find test specific information?

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

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?

Molecular PCR tests are for those with COVID-19 symptoms or recently exposed and at risk. These tests are used to indicate if the patient has an active COVID-19 infection.

Antibody serology tests are for those with no COVID-19 symptoms who may have been previously exposed to or overcome SARS-CoV-2. It may indicate prior infection which may be resolved, as well as potential immune response.

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.

What impact will antibody testing have on future decisions regarding the “return to daily life”?

The recent ACLA White Paper stated there are various factors that state and federal policymakers and officials must consider when making decisions about the return to daily life for individuals. Serology is one tool that can inform decisions about whether it may be safe to lift stay-at-home orders or provide a timeline for safe returns to the workplace, schools, and other common areas. Recent FDA guidance references experience with other viruses that suggests that individuals with antibodies—provided they are recovered and not currently infected with the virus—may be able to resume work and other activities.

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.

IgG antibody testing may be performed to assess whether an individual (eg, healthcare worker, student, general population, etc) has been exposed to SARS-CoV-2 in the past. If a serology test delivers a positive result for the IgG antibody, that means the individual was previously exposed to SARS-CoV-2 and may indicate prior infection which may be resolved, and/or protection against re-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 of 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.

Which Quest COVID-19 test should customers be using?

IgG antibody testing (test code 39504) may be performed to assess whether someone has been exposed to the SARS-CoV-2 virus in the past. IgG antibody testing should not be used to diagnose active infection, and symptomatic patients should always be diagnosed using a molecular COVID-19 test (test code 39448).

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.

  • 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

Testing statements

The antibody tests (sometimes known as the serology tests or IgG tests) are intended for use as an aid in identifying individuals with an adaptive immune response to SARS-CoV-2, indicating recent or prior infection. Results are for the detection of SARS-CoV-2 antibodies. IgG antibodies to SARS-CoV-2 are generally detectable in blood several days after initial infection, although the duration of time antibodies are present post-infection is not well characterized. At this time, it is unknown for how long antibodies persist following infection and if the presence of antibodies confers protective immunity. Individuals may have detectable virus present for several weeks following seroconversion. Negative results do not preclude acute SARS-CoV-2 infection. If acute infection is suspected, molecular testing for SARS-CoV-2 is necessary. The antibody test should not be used to diagnose acute SARS-CoV-2 infection. False positive results for the antibody test may occur due to cross-reactivity from pre-existing antibodies or other possible causes.

  • 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 or 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.