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Answers to your antibody testing questions

Last Modified: April 30, 2020

Family Medicine

Antibody testing

This post was written by Joshua Kline, MD, physician leader, PPG – Family Medicine.

For those who follow the news, you may have noticed that the word “antibody” has been everywhere. The testing process, and what it means exactly, can be a bit confusing for those outside of the medical sphere, so we’re taking the most common questions around the headlines and breaking them down a bit.

What is an antibody test?  What are antibodies to COVID-19?

Antibody tests are blood tests that look for the presence of antibodies. Antibodies are specific proteins made is response to an infection. Antibodies can be found in the blood and other tissues of those who were tested after infection. The antibodies detected by these tests indicate that a person had an immune response to SARS-CoV-2 which is the virus that causes COVID-19. Even if the person did not have symptoms from COVID-19 infection, those that were infected will develop antibodies. 

If I have the antibodies, do I have immunity to COVID-19?

No one knows for sure. Since COVID-19 is a new virus, scientists are still determining whether those that have antibodies have full immunity, only partial immunity or no immunity to future infections with COVID-19. In other words, we are still not sure whether having antibodies to COVID-19 from previous COVID-19 infection will protect you from future infections with COVID-19. We also do not know how long COVID 19 antibodies will last in your body. 

Who should get antibody testing?

While your doctor can order the antibody testing for you, this type of testing is not currently recommended for most people. These tests are new and many have not been validated by the U.S. Food and Drug Administration.

Currently, per the Indiana State Department of Health (ISDH), antibody testing is most helpful in identifying plasma donors who have recovered from COVID-19 infection to enroll them in studies to help develop possible treatment and vaccines. It can also help gather data on the prevalence of COVID-19 infection in the public. The ISDH is currently doing antibody testing for this reason. In the future, antibody testing will be used to verify response to COVID-19 vaccination. 

Antibody testing is not currently recommended for individuals to see if they have had infection with COVID-19 in the past because it is not always accurate, and it is not known if antibodies to COVID-19 are protective against future infection. It is important to understand that a blood test is not a test for active infection. If you have symptoms concerning for COVID-19 infection, you should have another type of test, a PCR test, done by a swab of the inside of your nose, to see if you have COVID-19 infection.

If I have antibodies does that mean I already had COVID-19?

It can mean that you have had the COVID-19 infection in the past. However, sometimes it can be a “false positive” meaning that the test shows antibodies even though that individual has never had COVID-19 infection and is not protected against COVID-19. One reason is that, for some of the tests, a positive result can mean you have been exposed to a different virus in the “coronavirus” family that is not the COVID-19 virus. There are 6 other coronaviruses that can affect people, and most of them lead to common cold symptoms. It takes around 10-18 days from exposure to COVID-19 for the body to produce enough antibodies to be detected in the blood.  

Why are we asking people with these antibodies to donate plasma?

Researchers are testing the use of donated blood as a treatment for people with severe COVID-19. People who have recovered from COVID-19 have antibodies to the disease in their blood. Doctors call this convalescent plasma. Researchers hope that convalescent plasma can be given to people with severe COVID-19 to boost their ability to fight the virus. 

Before donated blood can be used, it must be tested for safety. It then goes through a process to separate out blood cells so that all that is left is plasma with antibodies. The immediate goal of the current research is to determine if convalescent plasma can improve the chance of recovery for people with the most severe disease. A second goal is to test whether convalescent plasma can help keep people who are moderately sick from getting sicker.  If you have had and recovered from COVID-19, consider donating blood through the American Red Cross or your local donation center. They can provide information about the donation process.


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