Test doesn’t swab the blood-brain barrier
A Facebook post Monday claims that the area sampled during a COVID-19 nasal swab is a part of the body called the blood-brain barrier. An image accompanying the post associates the blood-brain barrier with the target site for sample collection.
The post says, “I was wondering why the PCR test for COVID-19 had to be so far back and it got me thinking ... how far does it go?
“So I did some research and found these two pictures and overlapped them. The surprising evidence was shocking!
“The blood brain barrier is exactly where the swab test has to be placed. “Coincidence??? I don’t think so.”
The author of the post has not yet responded to USA TODAY’s request for comment.
What is the blood-brain barrier?
Blood vessels are channels through which blood – the fluid providing the human body with vital nutrition, oxygen and waste removal – circulates. Some blood vessels surround the central nervous system, forming a specialized layer called the blood-brain barrier. It tightly regulates the movement of molecules, ions and cells between the blood and the central nervous system. It’s very restrictive nature has proved problematic for therapeutic drug delivery and many scientific efforts are investigating methods to bypass this vascular firewall.
So is the blood-brain barrier sampled during a COVID-19 nasal swab? Quite the contrary: It’s not even within anatomical reach.
“There are three layers of protection in the nose. There’s the mucosal lining which covers the inside of the nose. There’s the olfactory epithelium (involved in sense of smell). The inside, the dura mater, which means ‘tough mother,’ is a tough lining of skin around the brain. It’s hard to penetrate through (it) without something sharp,” said Dr. Shawn Nasseri, an ear, nose and throat surgeon in Los Angeles, in an interview with USA TODAY.
Nasseri, who has performed COVID-19 nasal swabbing countless of times in his own clinic, emphasized that piercing the dura mater to get to the blood-brain barrier with the typical soft swab used, even with poor sampling technique, was “very incredibly unlikely.”
Yvonne Maldonado, a professor of pediatric infectious disease at Stanford University School of Medicine who recently authored a study investigating COVID-19 self-swabbing tests, agreed.
“As far as we are aware, there is no scientific basis for the idea that nasal swabs can enter or damage the blood brain barrier,” she wrote in an email to USA TODAY.
And while some patients can have significant reactions, specifically fainting or light-headedness likely due to the “seal dive” reflex, illness due to olfactory epithelium injury during sampling is doubtful.
Our ruling: False
The blood-brain barrier, a system of vessels surrounding the central nervous system, is not readily in reach without piercing through several protective layers – an unlikely feat with a soft nasal swab. The additional claim that swabbing leads to damage in the olfactory epithelium is also unlikely.
Our fact check work is supported in part by a grant from Facebook.
“There is no scientific basis for the idea that nasal swabs can ... damage the blood brain barrier.” Yvonne Maldonado Author of a study investigating COVID-19 self-swabbing tests