Cincinnati Children's Blog

COVID-19: What We Know About Antibody Tests

COVID-19: What We Know About Antibody Tests

As we continue to learn more about the new coronavirus, COVID-19, many families are wondering if they’ve been exposed to it or have had the disease previously. I’ve heard many parents say, “You know, we were really sick back in February. I wonder if we’ve already had it?” Or, “Should my high-risk or immunocompromised child be tested before they attend school again?”

These are valid questions and many are also wondering if they should get a COVID-19 antibody test to answer them. Antibody, or serology, testing is a blood draw that checks to see if someone has had a past infection. Antibodies IgM and IgG are the proteins that we produce in our blood to help fight viruses. So theoretically, if someone shows COVID-19 antibodies in their blood, they may have been exposed to or had the disease.  

Unfortunately there is still so much we don’t know about COVID-19 and the antibody testing for it. We don’t have enough scientific evidence to make a recommendation for getting it. And we don’t yet know what to do with the information afterwards. Here’s what we do know about antibody tests:

1. They can show a prior infection

A positive antibody test can indicate that someone has had a prior COVID-19 infection. Most patients start to develop antibodies 1-3 weeks after they first become sick.  What we don’t know is if these antibodies will provide any immunity or help someone be less susceptible to another infection in the future. A positive test does not mean that someone currently has the virus. For that, you need a viral test in which your nasal/sinus area is swabbed to find an active infection by looking for the genetic material of the virus.

2. They’re not always accurate

Antibody testing for COVID-19 is not always accurate, as it is an area of active research. There can be false positives and false negatives. You can have a positive result even if you’ve never had the virus. Further, a positive test could show cross-reactivity with another coronavirus strain, but not COVID-19, such as HKU1, NL63, OC43, or 229E. A false negative could happen when a currently or recently infected person has not yet developed antibodies in response to the disease. We don’t know how long it takes for us to produce antibodies. And we don’t know how long they stick around in our bodies after an infection. Additionally, the tests only show positive and negative, not a range of numbers.

3. They can’t be used to make medical recommendations yet

We just don’t know enough about COVID-19 and the results of the antibody tests to make medical decisions based upon them. For instance, if you tested positive, we can’t say that you’re immune from getting it again. Meaning, we can’t say that it’s safe to hug grandma, attend a summer camp or return to school in the fall without worries of spreading it around or catching it another time. 

4. They could help us gain more information in the future

While we can’t use the results of antibody testing to make medical recommendations for patients currently, it could help us have a general understanding of how many people may have been exposed to the virus. In the future, this test may help us make medical decisions or understand how many people in a population have had the infection. But more research needs to be done before we can officially recommend using it in pediatric patients.

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