Making Sense of COVID-19 Testing

At Better, we’ve discovered that people need COVID-19 testing for all sorts of reasons. Surprisingly, the reasons our patients get tested is almost never that “I might have been exposed to COVID-19 and I want to get tested” or “I feel sick and I want to see if I have COVID.” Rather, the most common reasons that our patients ask us for COVID-19 testing are because their job requires it or because they’re traveling on a plane and the airlines or destination country requires pre-travel COVID testing.

The reason you’re getting tested is important because it dictates what type of test you should get. That’s why we here at Better ask and make sure what the reason for testing is. It turns out that there are 4 different COVID-19 tests (so far), which individually or as a combination, gives you different information about your COVID-19 status.

The 4 types of COVID-19 tests are:

  1. COVID-19 Antigen Testing
  2. COVID-19 Nucleic Acid Detection Testing (otherwise known as COVID-19 PCR testing)
  3. COVID-19 IgM Antibody Testing
  4. COVID-19 IgG Antibody Testing

Let’s go through each in order so that you know what type of testing best suits you and your needs

COVID-19 Antigen Testing: This test, as its name implies, tests for COVID-19 antigen. If you are positive, it means that you have an active ongoing COVID-19 infection and are probably contagious. Since COVID-19 is a respiratory tract infection, the sample taken for testing comes from your respiratory tract i.e. your nose via a nasal swab.

An “antigen” is simply one of the virus’s body parts. You can think of it as the virus’s arm or leg. And, just as a human leg is different from an elephant’s leg, COVID-19’s antigen is different from the antigen of any other virus, which is how the test is able to tell that you have the COVID-19 virus as opposed to the influenza virus or rhinovirus. The advantage of COVID-19 antigen testing is that it’s quick or “rapid.” You can get an antigen test result in as quickly as 15 minutes. The disadvantage is that it’s not particularly accurate. Some brands have created tests that are only as good as 85% accurate. Other brands are only 50% accurate (basically, a coin toss). So if you need an answer in a hurry, and aren’t too worried about potential false negatives, then antigen testing is for you.

COVID-19 PCR Testing: This test tests for the presence of COVID-19 genetic material. So, instead of looking for an arm, we’re now looking for DNA. PCR testing is much, much more accurate than antigen testing and is estimated to be 99% accurate under ideal conditions (though accuracy can fall significantly under non-ideal test conditions). The downside is that PCR testing takes much longer–at least several hours in the very best circumstances. Additionally, the PCR test can remain positive for up to 3 months after infection (which is why the FDA recommends only getting repeat PCR testing, if you’re so inclined, only at least months after your first positive PCR test). This also means that if you have a positive PCR test, you were infected with COVID-19 sometime in the past 3 months. If accuracy is important to you, then PCR is the test for you.

COVID-19 IgM Testing: IgM stands for “immunoglobulin M” and is one of the antibodies that your body produces in response to an infection. Your body normally starts to make detectable levels of IgM approximately 1 week after infection and stops making detectable levels of IgM at approximately 3-4 weeks following infection. Currently, the only practically useful purpose for obtaining an IgM level is for travel purposes as certain airlines and destination countries have mandated that travelers obtain IgM testing prior to being flight-approved. There are currently 2 methodologies that test for IgM–the first is via a blood draw from a vein and the second is via fingerstick testing. Though the manufacturers of fingerstick testing state that test results are at least 95% accurate, this is only true if the individual performing the test does so correctly. In our own investigation of these products, user-error accounted for a significant percentage of false-negative fingerstick test results, which then resulted in entire flights being canceled.

COVID-19 IgG Testing: As you’ve probably guessed, IgG stand for “immunoglobulin G”, another of your body’s antibodies. IgG is special because it is thought that this is the antibody that confers long-term immunity. However, how long “long-term” actually is is still under debate. One recent study published by the Royal College of London claimed that IgG levels dropped significantly after 4 months, but whether this translates into decreased long-term immunity is still unknown, because you don’t necessarily need large amounts of IgG in your body in order to have immunity.

 

The last thing to keep in mind when you’re doing your COVID testing is to make sure to use reputable test products and diagnostic laboratories as the quality of these can vary widely. Here at Better, we’ve taken every step that we can to make sure that your COVID testing is as accurate as possible. For this reason, Better only performs PCR testing and antibody testing via venous blood draw using accredited diagnostic laboratories.

 

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