Here's Why One Coronavirus Test May Not Be Enough
Experts caution against using one negative COVID test as a green light to go about your life as normal.
More than 47 million Americans have been tested for COVID-19, from those who head to the doctor after experiencing telltale coronavirus symptoms to asymptomatic individuals who need to get tested before returning to work. However, some people are using the test to determine which activities they can safely participate in—for instance, those who want to visit friends or family may take a coronavirus test prior to make sure they're not carrying the virus without knowing it. But according to experts, taking just one test for coronavirus may not be enough to green-light a return to normalcy.
"I personally wouldn't consider a single test a license to go see my parents, who are older and would be at higher risk," Carl Bergstrom, PhD, a University of Washington biology professor who studies infectious diseases, told The Washington Post.
Coronavirus tests can be administered in a few different ways: nasopharyngeal (deep nasal collection), throat, nostril, and saliva swabs. However, each has their limitations, and up to 25 percent of COVID tests could actually be inaccurate. According to Bergstrom, what ultimately makes coronavirus testing so unreliable is the fact that when you take the test matters, and unfortunately, "timing varies a lot in people." Even the Centers for Disease Control and Prevention (CDC) caution against taking a negative viral test completely at face value.
"You might test negative if the sample was collected early in your infection and test positive later during your illness," the CDC explains on their website. Bergstrom elaborated on that idea, saying for instance, if you were infected with the coronavirus today and immediately tested for it tomorrow, you might "have every reason to believe you're going to test negative, even though you're infected."
So how long should you wait to get tested if you may have been exposed to the virus? As Lucy Wilson, an infectious disease specialist and a professor at the University of Maryland Baltimore County, told The Washington Post, on average, most people take about five days to test positive for the virus or show symptoms after exposure. Wilson compares it to a pregnancy test, which can only detect certain hormones days or weeks after conception—meaning taken at the wrong time, you could get a negative pregnancy test result even if you are pregnant, while your coronavirus test may yield a false negative if it's not given during the appropriate timeframe.
So, if you're looking for one coronavirus test to give you the OK to see other people during the pandemic, you might want to reconsider. Unfortunately, neither Wilson nor Bergstrom put much faith behind the antibody test as an indicator that you're safe to see loved ones, either. In fact, many studies, like one recently led by researchers at King's College London, have found that coronavirus antibodies fade significantly over a short amount of time, and may not mean much in terms of long-term immunity.
"Right now, we don't really know what a positive antibody test means in terms of the degree to which you're protected," Bergstrom said. And according to Wilson, the country is "just not there yet with the accuracy of the antibody test."
The limitations of the coronavirus test and antibody test may make it seem like there is little hope to be had, especially seeing as there is no COVID-19 vaccine available yet. However, that's why experts are still pushing the significance of wearing masks and practicing social distancing as extra protection measures—especially as states reopen and people begin to see friends and family members once again.
"We can't all stop living our lives entirely, [but] we have to make decisions about the risk we want to take on," Bergstrom said. And for more on coronavirus testing, This Is the Type of COVID-19 Test You Should Be Asking For.