There is a lot of confusion among people about COVID-19 antibody testing. Most people think they test positive for COVID-19 if they test reactive for antibodies. Misconceptions are cleared up below.
What is a COVID-19 antibody test?
The COVID-19 antibody test is also known as a serology test, which is usually a blood test. The test shows whether antibodies against SARS-CoV-2, the virus that causes COVID-19, are present. The presence of antibodies in the blood usually indicates that our body is fighting or battling an infection. Antibodies help you fight infections and can protect you from getting the same infection again. How long protection lasts varies from disease to disease and from person to person.
Antibody test results are not used to diagnose someone with an active infection.
What are the types of antibody testing?
- IgM antibodies, which occur early in the infection. You will test positive for IgM antibodies if you have recently been infected and your immune system has started to respond 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 will appear later. These antibodies indicate that you have had COVID-19 in the recent past and have developed antibodies that can protect you from future infection. At this time, it is not known how much protection the antibodies can provide against reinfection.
Do we need to self-isolate if we test positive for antibodies to COVID?
- If you test positive for both antibodies (IgM and IgG) and have symptoms associated with COVID-19, an RT-PCR test is recommended to confirm whether there is an active infection. Isolation is recommended until you are symptomatic.
- If you test positive for IgG antibodies and have no symptoms, there is no need for isolation.
What if the antibody test is positive?
Below are some possibilities if you test positive for antibodies:
- You must have previously been infected with COVID-19.
- You can test positive for antibodies even if you have never had symptoms of COVID-19. An asymptomatic infection can cause such a result, in which case there will be no symptoms even if you were infected.
- You should talk to your doctor if it is positive because there are 2 types of antibodies as described above and know if there is any active infection based on the type of antibody tested and current clinical condition.
- There is a possibility that a positive result means that you have antibodies to another virus from the same family of viruses called coronaviruses.
What if the antibody test is negative?
There are several possibilities that can cause a negative result.
- You have a current active infection in which antibodies have not yet formed, and you should seek RT-PCR to confirm the diagnosis if you have symptoms associated with COVID-19.
- You may not have been infected with COVID-19 before.
- Some people may take longer to develop antibodies.
- The result can be wrong, which is a false negative.
- Because the vaccine is already out and soon most of the people will be vaccinated. If you are vaccinated, you may not see antibodies if you go for antibody testing.
Whatever the outcome, taking good precautions to prevent the disease is a must.
Links:
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
according to
Dr. Y. Alekhya: