Should You Get An Antibody Test? The Short Answer: No.

Jun 30, 2020

There's been a lot of buzz about antibodies and coronavirus. Should you get tested for them to see if you've had the virus and didn't know? If you have antibodies in your system are you basically in the clear? In last week's Facebook Live health interview Kara Lofton dug into these questions with Dr. Eric Houpt — an infectious disease specialist at the University of Virginia School of Medicine. This is an excerpt of that conversation that has been lightly edited for clarity.

Lofton: So to begin Dr. Houpt, how do antibodies work?

Houpt: We make them in response to an infection, but they last for a while, sometimes lifelong, sometimes not. The main purpose they serve is to prevent or reduce subsequent infections. So they're pretty amazing. It's great that we make them, and they help us fight off future infections.

Lofton: I think one of the things that people are confused about is that, my understanding of an antibody is like getting childhood chicken pox or like if you get a particular strain of the flu, that you are immune to that disease now. But reading about it, it sounds like that's not always the case, depending on the virus that we get, is that right?

Houpt: Yeah, it's not always the case. So it depends on the infection and it's just not clear for COVID whether antibodies tell us that someone is immune. It's likely if you look at most infections, however, generally antibodies do indicate some protection. And so we're all guessing that probably there is some protection if you have an antibody to COVID, but we just don't know that for sure. [We] might be wrong, and don't know how long it lasts.

Lofton: Some of the approaches that particular countries have taken to addressing the coronavirus pandemic, like Sweden is a good example, is to say, ‘okay, we're just going to let people continue life as normal, get infected, and once you've had it, we'll have herd immunity,’ meaning that if enough people have it, you're sort of protecting the population. But there's some new research that came out in the last two weeks that seems to suggest that's not the case. Can you talk a little bit about that?

Houpt: You know, there's been news about Sweden that they have “tried this approach to get to herd immunity,” but you need to have about 60 percent or more of individuals immune. Currently in Sweden, and in most parts of the world, there's nowhere near 60 percent of people with antibodies. So we're a long way from herd immunity it appears right now.

Lofton: How reliable are the antibody tests? Are there any that are better than others?

Houpt: That part isn't known because all these tests have been authorized by [the Food and Drug Administration] FDA and are being used by different labs, but I don't want to make it sound like the tests are hopeless. You know, I think that they're actually pretty good. So it's nothing unusual here with COVID. It's just that we're all so concerned about COVID that we're talking about this in such great detail, but this is true for every test that has ever been used. Nothing is 100% perfect.

Lofton: You know, from what I'm seeing, basically people are saying that there is actually a lot of variance with how reliable those tests are and that people shouldn't depend on them. Is that your opinion of the tests that are available right now?

Houpt: It is not recommended that anyone go out and get one of these serology tests, antibody serology, same thing. The CDC [Centers for Disease Control and Prevention] doesn't recommend it as a routine in anybody. There's the virus tests that actually tests for the actual virus, that's in the nasal swabs. And that tells you if someone actually is actively infected and there's virus their nose, throat. And then there's these antibodies that are blood tests that tell you if someone had been exposed in the past such that their body made antibodies. Maybe once in a while we'll use the serology if someone we think has COVID, but maybe they had it a couple weeks ago, but they're still sick. But other than that, doing a serology test to see who may have been exposed in the past to COVID is really for, for studies, for research, for surveillance, for different, maybe parts of the country to know how much COVID has been circulating. It's not really information that is going to be useful to an individual person.

Lofton: What I'm hearing is that people are like, well, I can go get an antibody test, then I know if I’ve had it and if I've got some immunity, which we've talked about, you know, maybe sort of a false sense of security in a way, because we don't know how long the antibodies stick around. But you know, so that maybe if I, if I have antibodies, I can go see grandma. So I mean, can people use antibody tests to sort of feel more secure about their ability to transmit and to be infected?

Houpt: The short answer is no. So take me for example. I don't think I have had COVID because I haven't had a flu-like illness in the past few months. My guess is that I haven't had it. So I go, I get a blood test. And it says, I'm negative. Okay, I should still do the precautions that I’m doing anyway. Let’s say I did it and I was positive. This happened to a friend of mine. I said “have you ever been sick?” and he said “no, not in the past couple months.” And I said “well it might be false positive, not very likely in you and these tests aren’t perfect, so maybe 50 percent chance it’s real, it’s also possible that it’s negative.” Should he feel more comfortable going out in public? I don’t think so. Because A. It might be a false positive and B. even if it was a true positive and he truly did have antibodies, like we said at the beginning, we don’t know if that means he’s completely protected.

Appalachia Health News is a project of West Virginia Public Broadcasting, with support from Marshall Health and Charleston Area Medical Center.