Dec 12, 2023

Will Swabbing Two Different Body Parts Give You a More Accurate Result COVID Test Result?

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You probably know the drill when it comes to at-home testing for COVID-19: Unwrap the swab, swirl it around your nostrils, put it in the container of liquid, and squeeze a drop of liquid test strip. In about 15 minutes, you'll get your result.

Ever since people started doing COVID tests at home, there have been questions about the best technique to use—and some people have suggested that it all comes down to where you swab.

One idea is that instead of just swabbing your nasal cavity, you should also get a swab sample from your throat. But will the dual-swabbing action actually give you a more accurate result on a COVID test? Could it give you an inaccurate answer? Here's what experts say.

Linda Yancey, MD, an infectious disease specialist at Memorial Hermann Health System in Houston, told Verywell that the swabbing technique you use on a rapid antigen COVID test depends on the kit.

You won't have to guess—each kit will have instructions for swabbing on the box and/or on the paperwork that comes with the test.

According to Yancey, the most important step in getting an accurate result on an at-home COVID test is reading and following the instructions that come with the kit. That includes swabbing only where the test instructs you to and waiting the set amount of time before checking your result.

“We are all impatient, but to get the best results you need to take the time," she said. "Another key to getting accurate test results is to make sure you get an accurate sample."

So, if a test kit only requires you to swab your nostrils, it won’t be enough if you swab briefly at the tip of your nose. "You need to make sure you put all of the cotton tip in and rotate vigorously for at least 10 seconds," Yancey said.

Yancey said that most of the rapid at-home COVID test kits in the United States have been tested and manufactured based on using nasal swabs—not swabs of the mouth, throat, or cheek.

“The swabs should be used only as designed," said Yancey. "If anything, swabbing the mouth is going to give less accurate results because the test was not designed to react to oral secretions."

The Centers for Disease Control and Prevention (CDC) also wants that if you do not follow the manufacturer’s instructions, your COVID test results could be incorrect.

Most antigen tests are designed to detect viral proteins. Yancey said that a certain amount of viral protein is needed for the test to give a positive result. When you swab your nose, the test is able to look for these proteins in the sample you get.

However, Yancey said that if you swab your mouth for an antigen test sample, you could run into a problem. Your saliva makes enzymes known as proteases that are part of the digestive process and, as such, can also break down viral proteins.

When you swab your mouth, you’re picking up the proteases that are already working on breaking down those proteins you're trying to get. If you then swab your nose, you’re swabbing your nose with proteases that aren’t normally present there.

If you have early or mild COVID symptoms, you may not have that many proteins for the test to detect. If you swab your mouth and have a bunch of those proteases in your saliva, "it’s going to overwhelm and break down those proteins before the test can register positive," Yancey said.

Some hospitals and clinics do swab the mouth and the nose for a COVID test, but Yancey pointed out that these are different tests that have been designed for nasal and oral samples.

“Running a test with body fluids that the test has not been designed to analyze is going to give less accurate results, not more,” she said.

The U.S. Food and Drug Administration (FDA) also cautions against swabbing your nose and throat for at-home rapid antigen tests. In a social media post, the FDA wrote: “FACT: When it comes to at-home rapid antigen #COVID19 tests, those swabs are for your nose and not your throat."

It's not just folks at home who have been curious about experimenting, either. Researchers have also looked at whether different swabs give different results, and come away with different opinions.

One study at a community COVID testing site found that nasal/throat swabs were able to pick up positive COVID cases and did not lead to more false positives—that is, results saying a person had COVID when they really did not.

A different study found that using a combined nasal and throat swab didn't pick up that many more positive COVID cases than nasal swabs alone.

Researchers and other experts who have debated different swabbing techniques point out that there are still a lot of unknowns about how combing nasal and throat swabs would work, and whether there's even any incentive for test makers to try to validate them.

For example, an increase in detection by only a few percentage points may not justify the work of trying to validate the test or have people add another step to the process—especially if it would mean having two separate swabs (one for the nose and one for the throat sample).

Adding another step could also make it harder for people to get a good enough sample to test, as well as introduce other factors into the testing process that could affect the results—like eating, drinking, or smoking before doing a swab.

What happens if you just swab your nose and throat anyway despite what your test kit instructs?

Dean Winslow, MD, a professor of medicine at Stanford University, told Verywell he does not think it will hurt to swab both places—especially if you know you aren't going deep enough when getting a sample from your nose.

“You’re not going to really affect the sensitivity of the test by swabbing a second area. It would be just like, in a way, swabbing two nostrils instead of one,” he said. “The nose and mouth are interconnected, anyway. Most of the same bacteria would be present in both places. So again, it probably doesn’t hurt to do so.”

While the nose + throat swab technique may not hurt, Winslow said that you should follow the test instructions to make sure that you get the most accurate result from an at-home COVID test.

It's also important to remember that the rapid antigen tests you can do at home are not as sensitive as molecular or PCR tests. If your first test is negative, you should repeat the test in a day or so. You may even need to take a third test, 48 hours after the second, if the second test is negative and you don’t have symptoms.

As an alternative to repeat rapid antigen testing, the CDC states you can get a PCR test through your healthcare provider or a local public testing center.

When you're testing for COVID at home, experts recommend following the instructions that came with the kit. While some people have experimented with getting a swab from the nose and the throat, it's not a guaranteed way to get a more accurate result and it actually could make the result less accurate.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

Centers for Disease Control and Prevention. Self-testing at home or anywhere.

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By Alyssa HuiAlyssa Hui is a St. Louis-based health and science news writer. She was the 2020 recipient of the Midwest Broadcast Journalists Association Jack Shelley Award.