Three Common SARS-CoV-2 Antibody Testing Myths Debunked

It can be hard to decipher fact from fiction when it comes to COVID-19. Here are three myths debunked surrounding SARS-CoV-2 antibody testing.
Three Common SARS-CoV-2 Antibody Testing Myths Debunked

Three Common SARS-CoV-2 Antibody Testing Myths Debunked

It can be hard to decipher fact from fiction when it comes to COVID-19. Here are three myths debunked surrounding SARS-CoV-2 antibody testing.

  • Antibody testing will tell me exactly when I was infected
  • False—however, an IgM assay will provide information about current or recent infection; while a separate IgG assay in addition will also give information about a more sustainable immune response.1

    Testing for IgM and IgG separately may be better than one combined test, as seroconversion is an individualized journey.2

    If a patient takes one antibody test (that tests for both IgG and IgM antibodies together), and the test comes back positive, the clinician does not know if the patient has been more recently infected or has an immune response to a prior infection.

    This is because, generally, IgM is the first antibody developed against an antigen and is detectable earlier, while IgG is developed later after the infection occurs and can be detectable for months and/or years, depending upon the antigen and the individual.3

  • If I take a PCR test (a diagnostic test that looks for an active coronavirus infection), I do not need to take an antibody test
  • False—while it is important to take a PCR test if you believe you have an active infection, studies are showing a high false-negative rate of real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) results for SARS‐CoV‐2 detection.4 In fact, a recent Johns Hopkins study found that the possibility of a false-negative from the PCR test is greater than one in five— and at times far higher.5 This study concluded, "If clinical suspicion is high, infection should not be ruled out on the basis of RT-PCR alone."6

    Therefore, complementing PCR testing with IgM testing can provide greater clarity into patient status.7

  • Antibody tests are not accurate
  • False—however, not all antibody tests are made the same. It’s important to ensure your antibody tests have high specificity and sensitivity to minimize false-positive results.8 Sensitivity refers to the test’s ability to correctly identify patients with COVID-19 antibodies, and specificity refers to the test’s ability to correctly identify patients without COVID-19 antibodies – it’s important to have both high sensitivity and high specificity in a test.

    Testing for IgM and IgG separately may provide physician’s more clarity into patient status when compared to one combined test, as seroconversion is an individualized journey.4

    Beckman Coulter’s IgM SARS-CoV-2 test has a specificity of 99.9% and a sensitivity of 15-30 days POS 98.3%; Beckman Coulter’s IgG SARS-CoV-2 test has a specificity of 99.6% and a sensitivity of >18 days 100% (75.8% <7 days).

1Chen, Y., & Li, L. (2020, March 23). SARS-CoV-2: Virus dynamics and host response. Retrieved August 03, 2020, from https://doi.org/10.1016/S1473-3099(20)30235-8

2Long, Q., Liu, B., Deng, H. et al. Antibody responses to SARS-CoV-2 in patients with COVID-19. Nat Med (2020). https://doi.org/10.1038/s41591-020-0897-1

3Partners In Health Guide | COVID-19. Part I: Testing, Contact Tracing and Community Management of COVID-19. Updated 20 March 2020. https://www.pih.org/sites/default/files/2020-03/PIH_Guide_COVID_Part_I_Testing_Tracing_Community_Managment_3_21.pdf, Accessed: May 7,2020

4Xiao, A., Tong, Y., & Zhang, S. (2020, July 11). False negative of RT‐PCR and prolonged nucleic acid conversion in COVID‐19: Rather than recurrence. Retrieved August 03, 2020, from https://onlinelibrary.wiley.com/doi/full/10.1002/jmv.25855

5Ercolano, A. (2020, July 23). Coronavirus Research: Johns Hopkins Medicine. Retrieved July 28, 2020, from https://www.hopkinsmedicine.org/coronavirus/coronavirus-research/

6Kucirka, L., Lauer, S., Laeyendecker, O., Boon, D., Lessler, J., & M. Centor, R. (2020, June 16). Variation in False-Negative Rate of Reverse Transcriptase Polymerase Chain Reaction–Based SARS-CoV-2 Tests by Time Since Exposure. Retrieved August 03, 2020, from https://www.acpjournals.org/doi/10.7326/M20-1495

7Xiao, Ai Tang et al. "False negative of RT‐PCR and prolonged nucleic acid conversion in COVID‐19: Rather than recurrence” Journal of Medical Virology, First published: 09 April 2020 https://doi.org/10.1002/jmv.25855

8Antibody Testing At-A-Glance Recommendations for Professionals. (2020, May 28). Retrieved August 03, 2020, from https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests-professional.html

Editorial Team
Editorial Team
The Beckman Coulter editorial team brings you timely news and resources focused on elevating clinical laboratory performance and advancing patient care.

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