Laurel WamsleyMay 31, 20207:18 AM ET
Earlier in this pandemic, the shortage of tests for the coronavirus was a major problem in fighting the spread of COVID-19. The shortage was such that many hospitals and clinics would test only someone who had traveled to a country with an outbreak, had a known exposure to a positive case or showed symptoms of the disease.
But access to tests has improved significantly, and in some places, people can now get tested without having to show any symptoms at all. So if you can get tested, should you?
The answer is a little complicated. One point to clarify: We’re talking here about the diagnostic or PCR test, used to diagnose people who are currently sick with COVID-19. We’re not talking about antibody or antigen tests, which are different.
The short answer to the question is: Sure, get tested if you want. But the tests are not perfect, and the result will tell you only so much.
Let’s say you test positive. Your doctor will likely instruct you to self-isolate at home. Since you’re not showing symptoms, it could mean that you happened to be tested at just the right time and are infected with the virus but are asymptomatic. You could also be presymptomatic and develop symptoms in the coming days. The CDC says that if you continue to have no symptoms, you can end self-isolation 10 days after your test.
A positive result could also mean you were sick weeks earlier, fully recovered and are not infectious. The PCR test has sometimes shown positive results weeks after someone recovers, says Dr. Abraar Karan, a physician at Harvard Medical School: “The test could be detecting RNA [of the virus] even in people who are recovered — but that doesn’t mean that they’re infectious.”
Now let’s say you test negative. That news would probably come as a relief. Perhaps you’re hoping a negative result would free you to do certain activities without fear — say, return to work or visit an older family member you haven’t seen in months.
But Dr. Emily Landon, a hospital epidemiologist and infectious diseases specialist at University of Chicago Medicine, warns that a negative test shouldn’t be seen as your ticket to stop being cautious.
“We don’t know how good these tests are in individuals who don’t have symptoms,” she says. “We know they’re pretty good at picking up COVID when it’s present in people who have symptoms. But we have no idea what a negative test means in an individual that doesn’t have symptoms.”
“We are certain that there are people who test negative even though they are definitely contagious,” she says. “A positive test can make us relatively certain that you are shedding COVID. But a negative test does not mean the opposite.” It could be that you were tested too early in the disease process or that the swab didn’t pick up your infection.
Landon says it takes at least three to five days after exposure to test positive. What’s more, some people test positive, then negative, then positive again. Hospitals often test people with symptoms twice to try to be more certain about the finding.
The imperfections in test results have made it difficult to know how often health care workers need to be tested, she says, because a negative test doesn’t mean you don’t have the virus or “that you can just stop wearing your mask and not worry about it anymore.”
In other words, she says, if you’re getting tested to get peace of mind, a negative test shouldn’t give you much peace of mind.
Nonetheless, Robert Hecht, a professor of clinical epidemiology at Yale University, offers “an encouraging thumbs-up” to anyone who decides to get tested for the virus just because.
“This idea that you should be both concerned about your own status and recognize that you can be infected without symptoms — and that states should try to make more testing capacity available for people like that,” he says. “I think those are all good things in general.”
From a public health perspective, Landon says, there is some value in the odd asymptomatic person being tested and finding out whether they do indeed have COVID-19. “It gives you a better idea of how many people are sick. It helps us to understand the test dynamics better. And anytime somebody is positive, you can remove them from the equation [of transmission],” she says, by taking precautions so they don’t infect others.
But since the negative test doesn’t tell you for sure that you don’t have the virus, it’s not a 100% guarantee that it’s safe to visit your 80-year-old grandparent.