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Test for COVID-19 does not involve collecting a sample from the blood-brain barrier

July 7, 2020 GMT

CLAIM: The nasal swab test commonly used for diagnosing COVID-19 involves obtaining a sample from a protective layer of cells known as the blood-brain barrier. Disrupting this area can result in inflammation to the brain. 

AP’S ASSESSMENT: False. The swab used in diagnostic COVID-19 tests does not touch the blood-brain barrier. Instead, it is placed in the nasopharynx, a cavity behind the nose where the highest yield of viruses can be collected. 

THE FACTS: The nasopharyngeal swab used to diagnose COVID-19 goes so far back into the nose that it can be uncomfortable, even causing some people’s eyes to water.

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But it won’t hurt the area known as the blood-brain barrier where blood vessels and the brain exchange important nutrients, despite social media posts that claim otherwise.

On Tuesday, Facebook posts viewed more than a million times shared a diagram of the nasopharyngeal swab test next to an anatomical picture of the brain, suggesting the swab disrupts the blood-brain barrier.

“The blood-brain barrier is exactly where the swab has to be placed,” the image read, with a raised eyebrow emoji. “Coincidence??? I don’t think so.”

“And this would be why they have pushed so hard for everyone to be tested regardless of if you even have symptoms,” one Facebook user sharing the image wrote.

However, Dr. Morgan Katz, an assistant professor of medicine at Johns Hopkins University, said these posts fundamentally misunderstand what’s happening when the test is conducted.

The swab “would have to go through layers of muscle and fascia, as well as the base of the skull, which is a thick bone, in order to get anywhere near the blood-brain barrier, and I would say that it is not possible,” Katz told The Associated Press. 

Instead of the brain, the test collects a sample from the nasopharynx, an area between the back of the nose and the back of the throat where respiratory viruses often live.

“That’s just a place where we expect to see the highest yield of respiratory viruses,” she said. 

It’s true that the blood-brain barrier is important for keeping harmful toxins out of the brain, and moving important nutrients into it. Viruses like meningitis can cause inflammation to the area. But a nasal swab would not have this result.

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“You’d be much more likely to have a risk of compromising your blood-brain barrier by being infected with a harmful virus than by obtaining the test for that virus,” Katz said.

While the nasopharyngeal swab is the most common way to collect a respiratory specimen that can be tested for COVID-19, the Centers for Disease Control and Prevention says it is one of five acceptable collection methods. Details can be found on the agency’s website.

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This is part of The Associated Press’ ongoing effort to fact-check misinformation that is shared widely online, including work with Facebook to identify and reduce the circulation of false stories on the platform.

Here’s more information on Facebook’s fact-checking program: https://www.facebook.com/help/1952307158131536