There has been a lot of recent talk about antibody testing for COVID-19 (remember, this is different than the swab test to detect if you currently have COVID-19; antibody testing is a blood test that is intended to show if someone has had the infection), and we have understandably started getting a lot of questions from patients wondering if their child should get tested for antibodies to SARS-CoV-2 (the coronavirus that causes COVID-19). Right now, the answer is essentially “no”, and we thought it would be helpful to explain why.
Questions with the tests themselves
There are currently lots of tests available on the market; very few have been validated by any federal body (FDA, CDC, NIH – for more information on this, see the following article). Some are even falsely claiming FDA approval. There is a lot of concern about accuracy with many of these tests. In addition to the regular issues surrounding testing (accuracy, quality of the methods and materials), another concern with these tests is whether they will be detecting antibodies to other coronaviruses (which cause some of the common colds seen every year). In the coming weeks, there should be some clarity about the best tests to use for detecting antibodies to SARS-CoV-2.
Questions about what the information means
Even if we assume the test being used is high quality and accurate, there still remain many questions re: what the information means. For instance:
- What level of antibodies is protective?
- Does the presence of antibodies indicate that someone is no longer to contagious to others?
- What antibodies is the test testing for (IgM or IgG or both/mixed)?
- What part of the virus are these antibodies being detected directed against and are these the important antibodies, i.e. are these ones that confer protection?
Additionally, because of strange truths of statistics, in areas with a relatively low prevalence of the disease (which may still be true of Central Florida), a positive test is more likely to be a false positive than it is to be a true indicator of having had the illness.
So if someone gets an antibody test that is positive and concludes that they might have had COVID-19, that is probably a reasonable assumption. However, it does NOT mean 1) that you definitely had it, 2) that you are no longer contagious, 3) that you cannot get infected with SARS-CoV-2, 4) that you can safely go around without a mask, unable to pass or catch the infection.
What situations is antibody testing currently recommended
Currently recommended uses include:
- Testing someone in whom COVID-19 is strongly suspected but had a negative viral swab
- Testing someone in preparation to donate plasma for the treatment of someone else currently sick
(To read more guidance on antibody testing, see the following from the Infectious Diseases Society of America)
Another use of these tests is for testing populations to try to get a more accurate idea of “seroprevalence”, i.e. how many people in a community might have already been exposed. These are widespread public health efforts and will hopefully be happening much more in the coming weeks-months. More useful for a population than for an individual. But currently there are too many questions about the tests available and what the information will mean to recommend testing. At this point the market and the enthusiasm have outpaced the science.
As with everything with our current situation, the recommendations will be changing over time. Antibody testing is almost certainly going to play a significant role in how we navigating this virus, but it does require a little patience right now. So stay tuned; we will provide updates as this evolves.
(If interested in reading more, see the following articles from the New York Times and Washington Post and Nature)