What Is a COVID-19 Antibody Test?

Reviewed on 2/1/2021

What Is COVID-19?

A COVID-19 antibody test is a blood test that looks for immune system markers (antibodies) specific to an immune response to the coronavirus. This test can tell you if you have been infected, but there is no way to know just from an antibody test whether you are contagious still or not.
A COVID-19 antibody test is a blood test that looks for immune system markers (antibodies) specific to an immune response to the coronavirus. This test can tell you if you have been infected, but there is no way to know just from an antibody test whether you are contagious still or not.

COVID-19 is a novel (new) coronavirus, not previously identified in humans, responsible for an outbreak of respiratory illness that became a global pandemic in 2020. COVID-19 is different from other coronaviruses that cause mild illness, such as the common cold.

How Is COVID-19 Diagnosed?

COVID-19 is diagnosed with a physical examination to check if patients have any of the hallmark symptoms of COVID-19, and a patient history which includes asking if the patient had any known recent exposure to the virus. 

If COVID-19 is suspected, a viral test in which a long swab is used to take a sample from the nose or throat is used, which is then sent to a lab for testing to diagnose the illness. Some tests are rapid and results are available within a few hours. Other tests may take several days to receive results.

What Is a COVID-19 Antibody Test?

A test that can determine if a person had a past COVID-19 infection is an antibody test. 

Antibody tests are not helpful in diagnosing current infections because it takes up to 3 weeks following infection for the body to produce antibodies to the virus. A positive antibody test is interpreted to mean a person has been infected with SARS-CoV-2, the virus that causes COVID-19, at some point in the past. It does not mean they are currently infected. 

When a person has antibodies to COVID-19 they may have some protection against re-infection, however, researchers do not yet know how much protection antibodies provide or for how long any protections might last. 

Antibody tests are not 100% accurate and there may be some false positive results (a person tests positive for COVID-19 antibodies but was not infected) or false negative results (a person tests negative for COVID-19 antibodies but had a past infection). 

If people receive positive results on an antibody test, the current Centers for Disease Control (CDC) guidelines state: 

  • If patients receive positive results on an antibody test but do not have symptoms of COVID-19 and have not been around someone who may have COVID-19, they are considered unlikely to have a current infection
    • These people may continue with normal activities, including work
    • They are advised to continue to take precautions to protect themselves and others against COVID-19 infection
      • Wear a mask
      • Socially distance: stay 6 feet away from others
      • Avoid crowds
      • Avoid poorly ventilated spaces
      • Wash hands frequently with soap and water for at least 20 seconds 
      • Cover coughs and sneezes
      • Clean and disinfect frequently touched surfaces daily
      • Monitor their health for symptoms of COVID
      • Get vaccinated to protect against COVID-19
  • If patients receive positive results on an antibody test and who currently have symptoms of COVID-19 or were recently sick, they should follow all guidelines to protect themselves and others  
    • To help prevent the spread of COVID-19: 
      • Stay home except to get medical care
      • Separate yourself from other people
      • Monitor your symptoms
      • Call ahead before visiting your doctor
      • If you are sick, wear a mask over your nose and mouth
      • Cover coughs and sneezes
      • Wash hands frequently with soap and water for at least 20 seconds 
      • Avoid sharing personal household items
      • Clean and disinfect frequently touched surfaces daily

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Reviewed on 2/1/2021
References
https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests.html

https://www.cdc.gov/coronavirus/2019-ncov/index.html

https://www.covid19treatmentguidelines.nih.gov/

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines.html