There is a lot of confusion among people about COVID-19 antibody tests. Most people think that COVID-19 tests are positive if the antibody tests are reactive. The misconceptions are cleared up below.
What is the COVID-19 antibody test?
The COVID-19 antibody test is also known as a serological test, which is usually a blood test. The test indicates if antibodies are present against SARS-CoV-2, the virus that causes COVID-19. The presence of antibodies in the blood generally indicates that our body is fighting or has fought an infection. Antibodies help you fight infection and can protect you from getting the same infection again. The duration of protection is different for each disease and each person.
Antibody test results are not taken into account in diagnosing a person with an active infection.
What are the types of antibody tests?
- IgM antibodies, which occur early in an infection. The IgM antibody test will be positive if you have recently been infected and if your immune system has begun to respond to the virus. When IgM is detected, you may still be infected or have recently recovered from a COVID-19 infection.
- IgG antibodies, which are more likely to 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 infections. At this time, it is unknown how much protection the antibodies might provide against reinfection.
Do we need to isolate ourselves if we test positive for COVID antibodies?
- If you test positive for both antibodies (IgM and IgG) and have symptoms related to COVID-19, it is advisable to perform an RT-PCR test to confirm if there is any active infection. Isolation is suggested until symptom free.
- If you have tested positive for IgG antibodies and do not have any symptoms, you do not need to isolate.
What if the antibody test is positive?
Here are some possibilities if you test 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 COVID-19 symptoms. An asymptomatic infection in which there will be no symptoms even if you have been infected, may be the cause of such a result.
- You should speak to your doctor if it is positive as there are 2 types of antibodies as explained above and to find out if there is any active infection based on the type of antibody tested and the current clinical condition.
- There is a chance that a positive result means you have antibodies to an infection with a different virus from the same family of viruses called coronaviruses.
What if the antibody test is negative?
There are few possibilities that can be the reason for the negative result:
- You have a current active infection in which antibodies have not yet developed and you should undergo 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 incorrect, which is a false negative.
- Since the vaccine is available now and soon, most people will be vaccinated. In case you are vaccinated, you will not be able to see the antibodies if you take an antibody test.
Whatever the outcome, it is imperative to take good precautions to prevent the disease.
References:
https://www.webmd.com/lung/antibody-testing-covid-19#1
https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests.html
By,
Dr. Y. Alekhya.
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