FDNY chief medical director answers 6 key questions about COVID-19 testing

Dr. David Prezant clarifies the difference between the two test types and what results mean for immunity


With COVID-19 news flooding the airwaves and internet, it’s easy to understand why people are confused about testing types, availability, accuracy – and what all this means for determining immunity.

For fire and EMS agencies, testing questions are all the more pressing, with the need to prevent further spread of the virus in the community and to confirm the health of their workforce.

Fortunately, an expert has offered insights to some common areas of uncertainty.

FDNY Chief Medical Director Dr. David Prezant released a video statement last week, answering six critical questions about COVID-19 testing. (Photo/Screengrab)
FDNY Chief Medical Director Dr. David Prezant released a video statement last week, answering six critical questions about COVID-19 testing. (Photo/Screengrab)

FDNY Chief Medical Director Dr. David Prezant released a video statement last week, answering six critical questions about COVID-19 testing. While directed at FDNY members, the discussion provides valuable insights that, in many cases, apply to departments across the county.

Dr. Prezant first clarifies the difference between the two primary test types: “For the government, the question is determining the number of people who were exposed since the start of this pandemic, and that is best done by a COVID-19 antibody test. But for [first responders], during a pandemic, the important question, especially if you are ill, is finding out if you actually have the COVID-19 illness and that is best determined by the COVID-19 RNA virus PCR Test.”

Dr. Prezant walks through the following testing-centered questions, noting which test applies and why, and sharing additional details:

Question 1: I feel ill, but am I infected?

Prezant explains that the COVID-19 RNA virus PCR test identifies current or recent infection and could determine the need for a specific treatment if and when one becomes available. “The COVID-19 PCR test looks for COVID-19 RNA virus particles in your nose or throat swabs and soon, possibly, in sputum or saliva,” he says. “A positive test means that RNA from the virus was detected and you are currently or recently infected with COVID-19.”

Question 2: Am I contagious to family, friends, coworkers or patients?

The COVID-19 RNA virus test will answer this question. “It identifies whether you can spread the viral infection and therefore the need for quarantine or isolation,” Prezant says. “… Symptomatic persons who test positive are contagious, especially during the first week. Later in the course of their illness, as symptoms improve, the test becomes negative. … You may be contagious early on, before your test turns positive. The test may remain positive for a little while longer than you actually feel ill. But, on most days, if the test is negative, you are not contagious, and if the test is positive, you are contagious. … Antibody tests do not tell us if you are contagious to family, friends or workers.”

Question 3: Was I exposed?

“Both the COVID-19 RNA virus test and the antibody test can confirm exposure if positive, but the antibody test requires about a month before [it can] become positive,” Prezant says. “The antibody test is useful in defining prior infection and current immunity.”

Prezant adds that the antibody test is a better test after the pandemic has waned, when the question changes to not whether you are ill, not whether you are contagious, but whether you were exposed and whether you are immune. “Likely, many of us were exposed and never even had symptoms, or thought it was the common cold,” he says.

FDNY’s Bureau of Health Services plans on doing the antibody test as part of members’ monitoring exams once annual exams restart. “By then, it will be properly validated, FDA-approved tests,” Prezant says.

Question 4: Have I developed immunity and, if so, is it long-lasting, and do I still need to wear PPE? And when will this antibody test become available?

“If the antibody test is positive, then you are likely immune; how long that immunity lasts can only be answered by repeating the test several years later,” Prezant explains. “And of course, you still need to wear PPE because while we believe the immunity is sufficient to prevent recurrence, no one is 100% certain of that. And, if you are immune, no one knows how long it will last.”

FDNY’s current plan is to include the antibody test at annual medicals because by then, members will have had adequate time to develop immunity and to get a properly validated test.

“Major labs and hospitals throughout the country have not yet endorsed [the various antibody tests currently available] for clinical testing,” Prezant says. “The best ones are in the final stages of research and validation.”

Question 5: Are these tests accurate?

Prezant explains that there is no perfect test, but using a test with your symptoms and your history can help achieve a correct diagnosis to determine treatment, quarantine and isolation options.

“Inaccuracies, what we call false negatives and false positives are more common when tests are first developed,” he says. “For the pandemic, the FDA relaxed requirements, allowing labs to start using tests before they were fully validated. As a result, we can’t be completely confident in how these tests perform. But soon that will be no longer a problem because the tests will be developed and validated even better. For example, it’s estimated that when the COVID-19 RNA virus test was first done in the early days, it was 30% false negative rate. But now, the test is very good. It’s far less than a 10% negative rate, especially if done early on when you have symptoms.”

Question 6: Will testing be used to determine my duty status and is it a requirement to return to full duty?

Prezant explains that duty status at FDNY is determined by symptoms, not testing: “The RNA virus test is informative, but symptoms are determinant. During a pandemic, symptoms are enough to determine whether you are infected, and given the false negative and false positive rates, symptoms are how we determine duty status. An RNA virus test is optional, and could be recommended in specific, unique circumstances. An antibody test is not useful for return to duty but, in the future, it will be useful for determining who will need quarantine if future exposures occur.”

Watch the full video here. 

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