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One of the biggest bottlenecks in testing people for the novel coronavirus has not involved complex machines to detect genetic material or molecular biology. It’s been a shortage of swabs to take samples.

On Thursday, the Food and Drug Administration announced that it would allow a broader range of swabs to be used in tests, including some made of polyester that should be far easier to manufacture.


“This action today demonstrates the ingenuity that results from FDA working in partnership with the private sector,” FDA Commissioner Stephen Hahn said in a statement. “The Trump Administration has been working side-by-side with our industry partners to fight this pandemic, and today is a great example of that work.”

The FDA also announced that US Cotton, the country’s largest manufacturer of cotton swabs, has developed a polyester-based swab fully compatible with Covid-19 testing. The firm plans to manufacture the swabs in “large quantities,” the FDA said.

Experts hope the moves will make the swabs “so cheap and accessible that we can make them available to anybody as soon as they have a cold-like illness,” said Dan Wattendorf, a physician who directs innovative technology solutions at the Bill and Melinda Gates Foundation, which gave technical advice on the studies that led to the decision.


The FDA on Thursday took other steps that could help speed up diagnostic testing. It now says that a sample can be collected simply by circling the swab in the nose, instead of sticking a longer swab much deeper into the throat through a nostril. That process is deeply uncomfortable and causes patients to sneeze, meaning that health care providers need to be wearing full protective gear.

The agency also said the swab can be done by a patient, instead of by a health care professional. And instead of being stored in viral transport media, a special solution that is in short supply, the FDA also now said that it is OK to use saline solution, which is much more readily available, if necessary.

“That’s really breaking down a lot of barriers when people have shortages,” said Ken Ehlert, the chief scientific officer of UnitedHealth Group, which conducted studies that led to the regulatory changes. “If you look at New York, they were days from being out” of basic materials like swabs and viral media, he said.

Yuan-Po Tu, a physician at the UnitedHealth Group-owned Everett Clinic in Everett, Wash., worked with the Gates Foundation to run studies on how various testing swab techniques compared. Quantigen, a diagnostics firm, was also involved in the study, the results of which were announced simultaneously with the changes in FDA policy.

Tu said the research has shifted how he practices at his clinic, where he now tests patients in their cars, having them swab their own noses.

“This can be done very quickly in our drive-through,” Tu said. “We can collect one person every three minutes. When we do it in a car, we’re using the car as the containment vehicle. It’s not only faster, it’s nicer and more user-friendly and it’s much safer for everybody involved.”

The material used in the swab can affect testing. The tests work by growing large amounts of the virus using a reaction called the polymerase chain reaction, or PCR. Q-tips, for instance, don’t work, in part due to the fact that the cotton on the tip contains its own DNA; cotton, after all, is a plant. The swabs that are currently used are nylon or foam. But the FDA’s expansion of permitted materials to some made of polyester could help reduce shortages.

Wattendorf, the Gates Foundation director, said that over the next few days he expects data on whether tests are still accurate after they are exposed to temperature extremes that would likely occur when sent through the mail. That could be a step toward the FDA allowing tests that people can send to diagnostic laboratories through the mail.

The 330 million people in America have about a billion colds each year, Wattendorf said, and testing returning to a semblance of normalcy could require running tests on many of them. Making sure there are enough swabs is an important step to making that happen.

“It’s really important the world knows about it,” Wattendorf said. “We want the manufacturers to know about it, we want the doctors to know about it.”

  • The current focus appears to be on sampling the antigen but I have not seen much on how rapidly a result is obtained.The latter is critical if such testing is to be the mechanism for allowing children to return to schools, open restaurants or bars, etc.

  • The headline of this piece may be overly alarmist about Phase I “sinking” due to testing inadequacies. Did anyone notice that during a paucity of available tests in CA and WA in late January, Public Health officials were spectacularly successful using traditional methods of case reporting, contact tracing and quarantine?

    Point 2: The success of Phase I may depend more upon thoroughly understanding the virus’ transmission vectors and their vulnerabilities to countermeasures, getting that information out saturation-style, and then high-compliance application of these vector-interruption tactics. I would note that we’re only 2 weeks into the CDC-Guidance calling for facial covering in all public iteractions. If indeed the virus rides on a cloud of spittle micro-droplets formed while speaking, hoping to be inhaled by the next host, then achieving 100% compliance with absorbant facial covering will deny the virus a vector only partially challenged in the earlier 6′ social distancing. (The facial covering PSAs MUST rule out the use of “valved” N-95s, since those masks don’t filter the exhalation).

    As Dr. Fauci explains over and over, receiving a negative PCR swab test is NOT an all-clear that you’ve dodged the bullet — you could get infected tomorrow or already be infected in the pre-shedding phase. What this suggests is that full-adherence to all recommended mitigations MUST CONTINUE following a PCR negative.

    I may be of a minority opinion, but I believe the pandemic can be broken ex vivo applying vector countermeasures, just as West African Ebola was driven off the map in 2014. In that dire situation, the real breakthrough was understanding in detail the vectors (direct contact with infected body fluids), spreading this knowledge, and caretakers adapting their behaviors accordingly. By the time the VSV-vaccine was delivered to Africa, there were already too few new cases to conduct a controlled study.

    In coming days and weeks, I expect to see similar breakthrough R&D discoveries about the SARS-Cov-2’s vector vulnerabilities outside the body. This information developed by bio-engineers can then be translated into viral-spread countermeasures, much more rapidly than anything the in vivo scientists are likely to produce.

  • I wouldn’t rely on swab–be it nasopharyngeal or throat. In a German study published March 5,, in Page 12 Figure 2, out of 9 patients, most of their swabs’ RNA copy numbers are very low (less than 100) beyond the 1st week after onset of symptoms. Sputum samples, OTOH, are mostly high even into the 3rd week, some the 4th. It has been widely reported that false negatives are 30% in the United States among symptomatic patients. I think this has to do with the problem of low RNA copies in swabs. With low RNA copies, the chance of the swab picking up detectable quantity of virus becomes a matter of luck. The consequence is then you have infected individuals who go home and go out to mingle and spread the virus around. CDC approves of sputum samples. Not sure why hospitals seem to pile on swabs, which are in short supply anyway. Maybe someone can explain to me why sputum sampling isn’t in widespread use.

    • I was wondering the same thing myself, given the swab shortage. My understanding (based on speaking to people, not on literature, so take it with a grain of salt!) is that many people have difficulty producing a true sputum sample and instead just spit into the tube. Stool seems to have detectable levels of viral RNA for longer as well, but obviously isn’t suitable for drive-through testing (though at-home sampling could work).

  • OMG. Lickety-split figure out how to avoid the lengthy process of mailing and detrimental delay in test results. There must be portable, on-site, direct-feed (lithium battery operated) handy test machines that avoid this stupefyingly old-fashioned “by mail” process. Seems a very worthwhile challenge for the techies linked to Bill & Melinda Gates & Microsoft.

  • So Mr. Wattendorf stresses that the world be told what so many already know – a simple swab material replacement? What a marvellous technological advancement, so unexpected? Groan.

  • Thanks for the story! An important clarification, though: PCR does NOT “grow large amounts of the virus” — it replicates short stretches of DNA that, in this case, are based on specific SARS-CoV-2 RNA fragments. No viruses are produced in the process!!

    • Understanding the false negative and false positive rates is definitely important for any test! But nasal swabs aren’t necessarily “garbage” just because they’re easier to acquire. I haven’t seen the data on nasal swabs vs nasopharyngeal vs otopharyngeal vs sputum samples, but I’m sure it’s in the literature, or at least as a “pre-print” if you want to compare test performance. And any test that puts healthcare providers at less risk is worth investigating, since patients can’t wear masks while being swabbed.

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