Antibody testing for Covid-19 is now available. Below I explain how antibodies are produced, what is their function, and how to decide if you should be tested. I also explain the current procedures for testing.
1 Antibodies are produced by the body in response to an infection, a foreign substance or object, a virus, a bacterium or a vaccine. Sometimes these antibodies give us lifelong immunity, such as with a measles infection. Sometimes they need regular boosts like a tetanus shot every 10 years. Sometimes they need annual boosts like flu shots. Influenza mutates/changes regularly.
2 Scientists know that there are several coronaviruses that have been in circulation throughout the world for years and cause mild upper respiratory infections, colds and the like. You probably have had one of them.
3 The challenge with this test is to determine if you have the antibodies to SARS-Cov-2, the coronavirus that causes the Covid-19 disease process. You can have antibodies if you were sick and recover. You can have antibodies if you were exposed and had no symptoms, but your body was fortunate enough to fight it off and you had what we call an asymptomatic infection.
4 Ig M is the antibody first produced, within days or a week of exposure and it gradually peaks and then tapers off toward zero over the next weeks and months. During this time, IgG is produced, which has a longer lasting effect and may indicate immunity to getting the same infection again. We don’t know how long IgG lasts for Covid-19 and we don’t yet know whether it provides complete immunity (protection) against re-infection and for how long that protection lasts. Based upon other coronaviruses, scientists speculate it could last six months up to a few years. No one knows for sure.
5 Here is a graph of the process of infection and antibody production over time. If you can’t see it here, I will post it also at my linked in site and on facebook.com/DSMDCulverCIty I may put it on my website as well schechtermd.com (see BLOG)
Explains the curve of IgM and IgG after infection
6 Should you get an antibody test?
a If you had a Covid-19 like illness in the last few months or if you were diagnosed with Covid-19 and have recovered, then you should get the antibody test to see what kind of antibody response your body has produced.
b If you may have been exposed to someone with Covid-19, even if you didn’t get sick, you may wish to get tested to see if you were infected and developed an antibody response.
7 The IgG test is more important because it looks at possible long-term antibodies to SARS-Cov-2.
8 The IgM test may be helpful to define a more recent infection.
9 Perhaps everyone should be tested prior to venturing out to a more open world over the next weeks and months. Eventually the antibody test may be available at huge scale via blood or even saliva!
10 The antibody test currently is a blood test, with blood drawn from the arm. I am less convinced of the accuracy of the rapid test, using a fingerstick to draw blood. But I may have an opportunity to test one kind of these soon.
11 Most people who want to be tested will contact Vanessa in my office via the portal or phone or her email and she and I will arrange for you to receive a lab slip. This can also occur in the context of a telemedicine visit.
12 Due to the volume of interest in this, I will not be drawing blood for the antibody tests unless you must be in the office for another reason. Most of my work each week is via telemedicine right now for everyone’s safety.
13 You can go to our favorite lab, Primex, which has great turn around times. But their drawing stations are in Tarzana and Van Nuys and some other locations not adjacent to Culver City. They are testing IgM and IgG. (PrimexLab.com/locations)
14 You can alternatively go to a Quest lab, which has more drawing stations and closer ones. But currently they only do IgG. (QuestDiagnostics.com)
15 You can also make a reasonable decision to wait to test until we have more information about the tests and their accuracy.
16 To receive your lab results, you will need to have a telemedicine visit with me. This is because of the complexity of interpreting these results. I will need to explain the meaning of the results to each patient and help them decide whether they should be retested. Sending you a written report of your results without a consultation would lead to too much confusion.
17 I have been fortunate with Primex lab to be able to get quick results on all my lab testing.
18 For example, we have had a small, but adequate, number of swabs tests for Covid-19 with a 24 to 48 hour turn-around time for those that have needed it. (We do a very limited amount of “parking lot” viral swab testing by appointment only). I would therefore prefer, at this time, for you to have a Primex test.
19 I will be monitoring the results from Primex and Quest and other nearby labs to determine which are the most accurate as the weeks go by. I may change my referral pattern accordingly.
20 Regarding the 15 minute tests done by fingerstick: I am still evaluating the accuracy.
I hope this is clear and Vanessa can answer your questions, as well. Stay healthy!
Yours Truly,
David Schechter, M.D.