MISCONCEPTIONS ABOUT COVID-19 ANTIBODY TESTING

There is a lot of confusion among people about COVID-19 antibody testing. Most people think that they are tested positive for COVID-19 if they test reactive for antibodies. The misconceptions are cleared below.

What is COVID-19 antibody test?

COVID-19 antibody test is also known as serology test which is usually a blood test. The test tells if there are antibodies present against SARS-CoV-2, the virus that causes COVID-19. Presence of antibodies in the blood usually indicates our body is fighting or has fought against an infection. Antibodies help you to fight against the infections and can protect you from getting the same infection again. How long the protection lasts is different for each disease and each person. 

Antibody test results are not taken into consideration to diagnose someone with active infection.

What are the types of antibody testing?

  • IgM antibodies, which happen early in an infection. You will be tested positive for IgM antibody if you have been infected recently and that your immune system has started responding to the virus.  When IgM is detected you may still be infected, or you may have recently recovered from a COVID-19 infection.
  • IgG antibodies, which are more likely to show up later. These antibodies indicate that you have had COVID-19 in the recent past and have developed antibodies that may protect you from future infection. It is unknown at this point how much protection antibodies might provide against reinfection.

Do we need to isolate ourselves if we are tested positive for COVID antibodies?

  • If you are tested positive for both antibodies (IgM and IgG) and have symptoms related to COVID-19, it is advisable to go for RT-PCR test to confirm if there is any active infection. Isolation is suggested till you are symptom free.
  • If you have tested positive for IgG antibody and don’t have any symptoms, no isolation is needed.

What if the Antibody test is Positive?

Below are the few possibilities if you are tested positive for antibodies:

  • You must have been infected with COVID-19 in the past.
  • You can test positive for antibodies even if you have never had symptoms of COVID-19. Asymptomatic infection in which there will be no symptoms even if you have been infected, can be the cause for such a result.
  • You have to talk to your doctor if it is positive, as there are 2 types of antibodies as explained above and to know if there is any active infection based on the type of antibody tested and current clinical condition.
  • There is a chance that a positive result means you have antibodies from an infection with a different virus from the same family of viruses called coronaviruses.

What if Antibody test is Negative?

There are few possibilities which can be the reason for negative result:

  • You have current active infection in which antibodies are not developed yet and you need to go for RT-PCR to confirm the diagnosis if you have symptoms related to COVID-19.
  • You may not have been infected with COVID-19 in the past.
  • Some people may take longer to develop antibodies. 
  • The result may be wrong, which is a false negative.
  • As the vaccine is out now and soon most of the people will be vaccinated. In case you are vaccinated, you can’t see antibodies if you go for antibody testing.

Whatever the result may be, taking good precautions to prevent the disease is a must.

References:

https://www.mayoclinic.org/diseases-conditions/coronavirus/expert-answers/covid-antibody-tests/faq-20484429

https://www.webmd.com/lung/antibody-testing-covid-19#1

https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests.html

https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/antibody-serology-testing-covid-19-information-patients-and-consumers

 By,

 Dr. Y. Alekhya.

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