Does That Test Work? What You Should Ask Before Getting Tested for COVID-19 or Its Antibodies

PSI’s Global Medical Director Dr. Eva Lathrop oversees PSI’s service delivery portfolio focusing on sexual and reproductive health. She also works in the maternity ward of a local hospital delivering babies in the time of COVID, and still finds time to council her PSI colleagues on how they can protect themselves from the novel coronavirus.

While all below assessments and commentary from Dr. Lathrop will evolve as she monitors what data the medical community is collecting regarding testing, we at PSI are comforted by her insights—and we wanted to share those insights with our readers.

PSI works to deliver healthcare solutions to our archetypal consumer, Sara, so that she can make healthy decisions for her and her family in over 50 countries around the world. Today, we are all Sara.

Thank you, Dr. Lathrop.

Figuring out how to live healthy in the time of COVID is an exercise in information overload. To cut through the chatter, here is a basic framework of what to think about when you ask the internet, or preferably your doctor, about testing.

DIAGNOSTIC TESTS

Diagnostic tests are exactly what they sound like—they diagnose whether you have the disease. Largely these are taken by using nasopharyngeal swabs. This is when a health worker sticks a very long cotton swab on a stick up your nose, which can feel like they’re about to scramble your brain. (Hold still, please.)

Most diagnostic tests are what we call polymerase chain reaction, or PCR tests. You may also have heard them called nucleic acid amplification tests (NAAT), genetic tests, or RNA tests. This is the test you will receive if you are getting tested for COVID now.

In the last few days, another type of diagnostic test has received FDA approval via the Emergency Use Authorization (EUA) called an antigen test. It also collects samples by nasopharyngeal swabbing, and it looks for the presence of protein fragments found on or inside the virus. While antigen tests may not be as accurate as PCR tests, this is an exciting development as antigen testing is generally simpler, faster, cheaper and therefore easier to bring to scale. As of now, the antigen test is not widely available outside of hospital system-based studies. But stay tuned as we continue to learn more over the coming days and weeks.

ANTIBODY TESTS

Antibody tests – and whether we should rush to get one – are top of mind for many of us. There is an overwhelming trove of information in the lay press, some good, some not so good, about antibody tests. There is also much discussion by various global leaders on whether these are the magic tests we need to help “open up economies,” and reduce other lock-down type restrictions. We all want to know if we have been infected with SARS COV-2, and if we become immune after infection, but beware of fake news out there before you rush to check your antibodies.

In the early phase of the COVID-19 response, the FDA allowed manufacturers to meet less stringent requirements when generating and submitting efficacy data of their test, before authorizing those manufacturers to take their tests to market. This was to spur rapid development of tests and thus better understand the pandemic. Subsequently, over 200 antibody test options came to market very quickly without data on the sensitivity, specificity, and validity of the products. Eventually, it became clear that a large number of these new tests were not sufficiently accurate, i.e. many of those tests are useless.

The FDA has since changed its criteria. Today, for a test to obtain a “new” emergency use authorization (EUA), manufacturers must put forth their data demonstrating high sensitivity and specificity.  No EUA = no access to US healthcare markets. This course correction reduced the number of reliable antibody test options to 12 at the time of this writing. Many doctors’ offices, clinics, urgent care systems and hospitals have one of these 12 antibody tests available.

So should I take an antibody test?

First consider: what are you getting this test for? For most people the question is simple: have I been infected? But most also want to know—am I immune?

There is no test that can tell you that you are immune to COVID-19. A positive antibody test tells you that at one point you were infected. The good news is that the data the medical community has collected to date shows that most people who have been infected with SARS COV-2 do produce the specific antibodies, but right now, the story stops there. Expert opinion from scientists is that there is likely some immunity conferred from infection, but it is not yet known how much antibody is needed to reach immunity (or what “antibody titer” is needed), or how long the immunity will last.

I would still like to take an antibody test. What next?

First, try to get tested at a location that is looped into a study, which can then use the information gained from your test to answer some outstanding and critically important questions. Mostly, this means hospital systems and providers connected to hospital systems of the public health labs in your area. This will allow those systems to:

  • Find donors who could provide antibodies for convalescent serum
  • Figure out what the prevalence of the disease is in your local population
  • Establish the correlates, i.e. the titer of antibody needed to confer immunity—and how long that immunity lasts

Second, ask your healthcare provider: what test are they using? Remember all those fake tests that came to market under those lax FDA restrictions? You want to find out whether the test you’re being offered has a recent EUA. Also, can the provider administering it tell you what the sensitivity, specificity, and validity of that test is? It’s ok to ask these questions, and they are important for you to know. If they can’t, look around for a testing center that can.

At PSI, we work to track, test, and treat outbreaks in over 50 countries, both during pandemics (Ebola, cholera, Zika), and in high-risk zones for infectious diseases (malaria, HIV/AIDS). We are on the ground implementing COVID prevention measures in nearly all countries where we serve. Part of that critical work is getting the right healthcare information to the right people at the right time to ensure healthy behaviors, and to encourage social behavioral change for Sara and her family where needed. We are incredibly lucky as an organization to afford our staff the same level of quality information that we bring to the field. We offer you this small segment of our weekly internal briefing in the hopes that it will help you and your loved ones in this critical time.

Banner image: CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time Reverse Transcriptase (RT)-PCR Diagnostic Panel. Credit: US Centers for Disease Control/Wikimedia Commons

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