Should You Get The New Antibody Test for Covid-19?

Before I answer that, let me give you a quick tutorial about your immune system and how it deals with any virus–Covid-19, measles, hepatitis, seasonal flu, even the common cold. The mechanics of your immunity, which has kept you alive all these years, is pretty much the same from virus to virus.

If you read more on the subject these days, you’ll encounter the word serology, which is the science of studying serum, the liquid part of your blood. To extract serum, your blood is drawn, allowed to clot, and then spun in a centrifuge. The yellow liquid floating above that glob of a blood clot is serum, and a sample of this is what’s used to test for Covid-19 antibodies, which your body makes if it’s been exposed to the virus.

The hero of your immunity against viruses is the lymphocyte, a type of white blood cell. Another white cell, the neutrophil, kills bacteria, and is not overly involved with viruses.

When confronted with a virus, your lymphocytes grind out protein molecules called immunoglobulins (abbreviated Ig) that can destroy viruses. The different types of immunoglobulins are named according to letters of the alphabet.

IgM appears first, usually measurable in a couple of days, seemingly to jumpstart the battle ahead. IgM then slowly disappears, to be replaced by the more long-term IgG. Ideally, IgG stays with you forever, a lasting member of your immune library, so to speak, and will protect you if you ever encounter that virus again.

The sentence you just read is at the very heart of the issue of long-term protection from Covid-19. What happens in winter, 2021 depends on the strength of our IgG against Covid-19.

Are you following?
All this says something about the science behind immunization, in which you’re deliberately given a small and harmless amount of the infecting virus (polio, measles, etc.) to trigger an IgG immune response to protect you. The term for this process of deliberately infecting you is vaccination and the material used is, of course, called a vaccine.

The vociferous group against immunization are the anti-vaxers you’ve read about, although something tells me that when a Covid-19 vaccine becomes available they’ll be standing in line to get it just like everyone else.

Ideally, if we can vaccinate a majority of any population against a specific virus, that virus becomes so weakened that the disease disappears. This is how we got rid of polio. The term for this is herd immunity. With everyone else immunized, herd immunity protects even the anti-vaxers, who rightfully acknowledge they’re relying on the kindness of strangers (who vaccinate their children) to keep their kids from getting ill.

Physicians have been using the science of serology not only to protect us all from viruses, but also to diagnose viruses themselves. We routinely diagnose measles, hepatitis, and mononucleosis, among many others, by measuring IgG antibodies.

The long and short of it is…
Your immune system responds to the Covid-19 virus like it would to any other—namely, by grinding out IgM and IgG antibodies.

The only problem is that Covid-19 is much meaner and much harder for your immune system to obliterate.

In fact, while your lymphocyte count routinely increases (to create more IgG) while fighting any virus, when someone is losing the battle against Covid-19 the lymphocyte count goes down, a situation eerily called lymphocyte exhaustion. 

How to get tested
I did get tested and will share my results below.

Although there are hundreds of companies touting their Covid-19 antibody tests, if you don’t want to pay for testing you might as well stick with the test your insurance will cover.

On April 27, we received word that Northwestern Memorial Healthcare, which operates our office lab, has chosen to work with Viracor, a 30-year-old company with much clinical experience in serological diagnosis. You’ll get both the IgM and IgG from a blood draw. If you don’t have insurance, the self-pay price is a reasonable $90.

WholeHealth Chicago patients can call and schedule a lab-only. Make your appointment for around 9 a.m. as the serum needs to be shipped early in the day. Do not schedule if you’re feeling ill.

If you think you might have Covid-19, go to a testing center. We’re referring infected patients 100 yards north to Innovative Express Care. Thanks for not coming to our clinic if you think you have the virus. We don’t have any test kits and you’ll probably just manage to infect our staff if you come in.

Antibody testing not accurate for diagnosis
Because it takes several days for your immune system to generate enough antibodies to actually measure (three days for IgM, eight days for IgG), antibody testing is not considered an accurate way to diagnose an active Covid-19 infection. For that, it’s the nasal swab, which looks for actual genetic bits of the virus.

If your swab is positive for Covid-19, you’ve got it, period. No discussion. If your swab is negative, you probably aren’t infected, but you might have had an inadequate nasal specimen. This is called a false negative.

Results from an antibody test are different
If your antibody test is negative (no IgM or IgG), then most likely you’ve never been exposed to Covid-19.

However, a negative test does not completely rule out infection. You may have an early-stage infection—one that’s still incubating inside you, making you a symptom-free spreader of Covid-19. If this is the case, your immune system hasn’t had time to develop antibodies so you get a negative test result. Or you once had an infection so mild that your immune system isn’t picking it up.

When you realize you’re feeling ill, you can try to get a swab test and it’s a couple of days later that your first IgM antibodies appear.

If your antibody test is positive, then sometime in the past few months you were exposed to Covid-19. If you don’t remember feeling ill, your immune system obliterated the virus without you even knowing it. If you do remember something flu-like, that was your total experience with Covid-19.

If you know for certain that you had Covid-19 (as diagnosed with a positive swab), then having antibodies simply shows that your immune system is working. If you’re reading your positive antibody report and you had a Covid-19 infection, pause for a moment to thank your immune system for the exceptional job it did, your personal first responder.

The one fact we know about antibody testing
In any group of random people (grocery shoppers, those who showed up after answering a phone survey), 10 to 20%  test positive for Covid-19 antibodies without ever remembering being ill.

The remaining 80 to 90%, with no antibodies, were never exposed and are likely vulnerable to infection.

The three questions we can’t answer about antibody testing
1–Does having a positive antibody test protect you when you’re exposed to the virus again? We don’t know. Some viral antibodies (measles, mono) confer lifelong protection in most people. Others, such as seasonal flu, do not. If you have a positive antibody test result, are you entitled to a so-called Covid-19 Immunity Passport, meaning you’re a safe person to be working in an office, getting a restaurant reservation, or being admitted to a Big Ten football game? Again, we don’t know.

Currently there is no evidence that you can’t get Covid-19 twice. For now, you must continue to follow all the social distancing steps, frequent hand-washing, and mask-wearing.

2–Are the antibodies useful in any way? Can the serum from someone who is positive be used to treat another person with Covid-19 infection? We don’t know. Using serum as therapy has been around for 130 years, mainly for bacterial infections and before the invention of antibiotics. Using serum for a virus like Covid-19 is new but being tested.

3–Do the antibodies stay around for a while (conferring lifetime immunity) or will they disappear in a few months and leave you vulnerable to getting hammered by Covid-19 this winter? We just don’t know.

To satisfy my own curiosity, I had the test run on my serum and it came back negative, as had my nasal swab three weeks ago. So much for that. I was hoping to be among the positive 20%, but it turns out I’m still just as vulnerable to Covid-19 as most people. Glad I’ve been keeping up on my immune boosters, wearing my face mask, and obsessively washing my hands.

Undeniably, I’m beginning to feel a bit sorry for my ears. Not only are they looped by the elastic straps of my facemask, but they also support my hearing aids, eyeglasses, and Bluetooth headphones.

Be well,
David Edelberg, MD