As the COVID-19 pandemic continues, public health experts have repeatedly stressed the importance of a good testing strategy in slowing the spread of the virus. Even though you’ve been hearing about coronavirus testing for months, you might be a little fuzzy on the details.
First, know this: There are many different testing options out there, and while some are more accurate than others, none of them are perfect. Each type of coronavirus test has its own ~thing~ going on, but given that you probably didn’t go to medical school and that there are new updates in testing all the time, it can be hard to keep track of everything.
Whether you need to get tested for COVID-19 or simply want to read up on the ins and outs of coronavirus testing, here’s what you need to know. (If you have symptoms, also read: What to Do If You Think You Have the Coronavirus)
What are the most common types of COVID-19 tests?
In general, there are two main types of diagnostic tests for SARS-CoV-2, the virus that causes COVID-19. (“Diagnostic” means the tests are used to see if you currently have the virus.)
Both tests can detect an active COVID-19 infection, but they are different, according to the Food and Drug Administration (FDA). The FDA breaks it down this way:
- PCR test: Also called a molecular test, this test looks for COVID-19’s genetic material. Most PCR tests involve taking a patient’s sample and shipping it to a lab for analysis.
- Antigen test: Also known as rapid tests, antigen tests look for specific proteins from the virus. They’re authorized for point of care, meaning the test can be done in a doctor’s office, hospital, or testing facility.
If you visit your primary care physician for a test, you’ll likely get a PCR test, says Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. “Some offices do have antigen tests, though,” he adds. Which test you’re given usually depends on what your doctor has in stock, their personal preference, and your symptoms (if you have any). “The antigen test isn’t FDA-approved for asymptomatic screening yet, and many doctors won’t order the antigen test for someone without symptoms,” explains Dr. Adalja.
At-home coronavirus tests are another option. In mid-November, the FDA authorized the first at-home COVID-19 test, called Lucira COVID-19 All-In-One Test Kit. Lucira is similar to a PCR test in that both look for genetic material from the virus (though Lucira’s molecular methodology is “generally thought to be less accurate” than that of PCR tests, according to the New York Times). The kit is issued via prescription and allows people aged 14 and older to test themselves at home with a provided nasal swab. From there, the swab is inserted into a vial (which also comes with the kit), and you get results within 30 minutes.
What about COVID-19 antibody tests?
To date, the FDA has authorized more than 50 coronavirus antibody tests that can determine whether you were previously infected with COVID-19 by looking for the presence of binding antibodies — that is, proteins that bind to a virus (in this case, COVID-19). However, the FDA says it’s unclear whether the presence of these binding antibodies means a lower risk of future COVID-19 infection. Translation: Testing positive for binding antibodies doesn’t automatically mean you can’t get reinfected with COVID-19.
Not all coronavirus antibody tests detect the same types of antibodies, though. One test, called the cPass SARS-CoV-2 Neutralization Antibody Detection Kit, looks for neutralizing antibodies rather than binding antibodies. Neutralizing antibodies are proteins that bind to a specific part of a pathogen, according to the FDA. Unlike binding antibodies, the neutralizing antibodies detected in this COVID test have been found in a lab setting to decrease SARS-CoV-2’s viral infection of cells. In other words, if you have neutralizing antibodies, it’s unlikely that you’ll be infected with COVID-19 again or that you’ll develop a serious case of the virus, as long as those antibodies are still present in your body, according to the FDA. Research published in the medical journal Immunity suggests that neutralizing antibodies can remain present in the body for as long as five to seven months after a COVID-19 infection.
That said, the FDA notes that the effect of neutralizing antibodies on SARS-CoV-2 in humans is “still being researched.” Meaning, testing positive for any type of coronavirus antibodies doesn’t necessarily mean you’re in the clear. (More here: What Does a Positive Coronavirus Antibody Test Really Mean?)
How do they test for coronavirus?
There is some variation, depending on the type of test you’re getting. If you’re having an antibody test done, you’ll need to give a blood sample. But things are a little different with a diagnostic PCR or antigen test.
A PCR test is usually collected via nasopharyngeal swab, which uses a long, thin, Q-tip-like structure to sample cells from the very back of your nasal passages, or a nasal swab, which is similar to a nasopharyngeal swab but doesn’t go back as far. However, the FDA says PCR tests can also be collected using a respiratory aspirate/lavage (i.e. nasal wash) or saliva sample, depending on the test. An antigen test, on the other hand, is always taken with a nasopharyngeal or nasal swab.
In most situations, you’re going to get tested via nasopharyngeal swab, says Dr. Adalja. “It’s not comfortable,” he admits. “It’s much different than putting your finger up your nose or putting a Q-tip in your nose.” You may get a slight nosebleed afterward, and some people refuse to get the test based on that discomfort, says Dr. Adalja. But that momentary irritation is a small price to pay for a strategy that’s crucial to mitigating the spread of COVID-19, he notes.
How accurate are COVID-19 tests?
Coronavirus test accuracy depends on a lot of different factors. First, the type of diagnostic test you get matters. “The PCR test is considered the gold standard,” says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine. “If you get the timing right and you’re positive or negative on one of those, you’re probably really positive or negative.”
The rapid antigen test is a little different. “They’re notorious for giving false-negative results [meaning the test says you don’t have the virus when you actually do],” says Dr. Schaffner. Considering as many as 50 percent of all COVID antigen tests can yield false-negative results, “you have to interpret them with caution,” explains Dr. Schaffner. So, if you were recently exposed to someone with COVID-19 and you test negative with a rapid antigen test, you shouldn’t be entirely confident that you’re really negative, he says.
Timing matters too, says infectious disease expert Debra Chew, M.D., M.P.H., an assistant professor of medicine at Rutgers New Jersey Medical School. “If you’re early in your illness, you may not actually show a viral marker where the test would be positive,” she says. “On the other hand, if you present very late for testing, you may also be negative, even if you really had the virus.”
Wondering what, exactly is considered “early” or “late”? A recent analysis of seven studies published in the academic medical journal Annals of Internal Medicine puts this timeline in perspective: The probability of a false-negative PCR test result decreases from 100 percent on day 1 after exposure to 67 percent on day four. And on the day that someone develops symptoms (on average, five days after exposure), the research found that they’re about 38 percent likely to get a false reading. That probability decreases to just 20 percent three days after showing symptoms — meaning your coronavirus PCR test results are most likely to be accurate if you’re tested around five to eight days after exposure and about three days after showing symptoms, according to the analysis.
Basically, the longer you wait, the better — within reason, says Dr. Schaffner. If you know you’ve been exposed to someone with COVID-19, he recommends waiting up to six days after exposure to get tested. “Most people who are going to turn positive will turn positive on day six, seven, or eight,” he explains.
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How much does it cost to get tested for coronavirus?
It depends on where you go. If you visit a coronavirus testing site, it should be free, regardless of whether you have health insurance, says Dr. Adalja. If you visit your primary care physician or another medical provider, the test itself should be covered by insurance (though you can still expect to be responsible for a co-pay), says Richard Watkins, M.D., an infectious disease physician in Akron, Ohio, and a professor of internal medicine at the Northeast Ohio Medical University. “If you’re concerned, you can call the number on the back of your insurance card and confirm,” adds Dr. Watkins. (Here’s how telemedicine is evolving during the COVID-19 pandemic.)
If you don’t have health insurance but you go to a doctor’s office or hospital for a coronavirus test, you’ll typically be responsible for the cost of the whole visit, says Dr. Schaffner. That can get prettttty expensive depending on where you go (think: anywhere between $20 and $850 per test, and that doesn’t include other fees that may be part of the visit).
As for where to get tested for coronavirus, again, coronavirus testing sites (i.e. health centers in your community) are your best bet since they’re free. CVS, Walgreens, and Rite Aid are also operating pop-up COVID-19 testing sites (which may or may not come with out-of-pocket costs, depending on your insurance status). Be sure to look at your state and local health departments’ websites for up-to-date details on coronavirus testing near you.
How long does it take to get COVID-19 test results?
Again, it depends. It can take several hours or several days (sometimes a week or more) to get the results of your PCR test, depending on how backed up your local lab is, says Dr. Schaffner. Antibody tests can also take several days to weeks to get your results — again, depending on the lab it’s sent to.
Antigen tests, on the other hand, can give you results in less than an hour, according to the FDA. But again, this method, while speedy, isn’t considered as accurate as a PCR test.
Overall, experts recommend taking your coronavirus test results with a grain of salt. “Being negative means you were not infected at the point in time that the test was done,” explains Dr. Watkins. “You could have been infected in the interim.”
If you test negative for the virus but you’re having symptoms of COVID-19, Dr. Chew recommends reaching out to your primary care physician about whether you should get tested again. (Related: When, Exactly, Should You Self-Isolate If You Think You Have the Coronavirus?)
While testing is better than it was at the start of the pandemic and there are more options now, just keep in mind that it’s still not a perfect process. “People look for absolute answers [in this pandemic],” says Dr. Schaffner. “And we can’t give that to them with COVID-19 testing.”