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VERIFY: Throat swab vs. nasal swab for omicron

Is a throat swab better at detecting omicron than a nasal swab?

ATLANTA — People continue to wait in line for tests while trying to find available at-home tests in this latest COVID-19 case surge. But, just as people were getting used to the idea of swabbing their noses (sometimes multiple times a day or week) to find out if they’re infected, a new idea has been introduced.

On TikTok, user and journalist Allison Hall posted a video of herself receiving a negative result after swabbing her nose, then a positive result after swabbing her throat. Her positive result was confirmed by a PCR test.

Then the hashtag #swabyourthroat popped up on Twitter in recent days.

So, is a throat swab better at detecting omicron than a nasal swab?

SOURCES:

The Food and Drug Administration

U.S. researchers non-peer reviewed study

Epidemiologist Michael Mina

Faculty of Medicine, The University of Hong Kong

Department of Public Health

National Health Laboratory Service, South Africa

Epidemiologist Eric Feigl-Ding

Dr. Roy Gulick

ANSWER:

Needs Context

WHAT WE FOUND:

A recent study from a group of U.S. researchers found nasal swabs didn’t detect omicron for one to two days after infection. The study involved 30 people and showed saliva tests (throat swab) picked up a positive result before a nasal swab did.

The study, which hasn’t been peer-reviewed or published, concluded “Omicron has been shown to infect faster and more efficiently than Delta in human bronchus, but with less severe infection in lung, translating to symptom increase of sore throats and decrease of loss of taste and smell, better detected by saliva than nasal swabs.”

There’s evidence to support omicron doesn’t get as deep into the lungs as the delta variant.

Researchers at the University of Hong Kong’s Faculty of Medicine published a study showing omicron replicated 70 times faster in the airways and is less severe in the lungs.

A study from South Africa, which also hasn’t been peer-reviewed or published, showed throat swabs detected all omicron cases but 71% of delta infections, while nasal swabs detected 86% of omicron infections but 100% of delta cases.

Throat swabs are used outside of the U.S. in combination with nasal swabs to test for COVID-19.

Boston-based epidemiologist Michal Mina said over Twitter, “This is fairly standard in UK *In US it is NOT FDA authorized to do a throat swab. Does likely improve sensitivity. May potentially cause a slightly greater number of false positives. Don’t drink or eat for 30 mins before.”

So, why the context? 

First, the studies previously referenced included small samples of people.

Second, the FDA stands by nasal swabs for now, adding it may be complicated to self-administer a throat swab accurately.

"The FDA advises that COVID-19 tests should be used as authorized, including following their instructions for use regarding obtaining the sample for testing. The FDA has noted safety concerns regarding self-collection of throat swabs, as they are more complicated than nasal swabs – and if used incorrectly, can cause harm to the patient."

Third, a nasal swab can still be part of the test. Usually, the throat swab is administered first, then the nasal swab. And not all at-home tests in the U.S. may work for both.

“The microenvironment of the nose is different than that of the throat, so not all tests are going to be valid in both places,” Dr. Roy Gulick, Chief of the Division of Infectious Diseases at New York-Presbyterian/Weill Cornell Medical Center told TODAY.

Epidemiologist Eric Feigl-Ding also told TODAY, “it’s not that an at-home test won’t pick up omicron in the noses when swabbing there, it just might pick it up a half a day or a day later.”

So, there's some evidence to support a throat swab showed a positive result for omicron faster, but there's also evidence to show nasal swabs work well for the majority. And evidence to show nasal swabs detect all delta infections. 

What should you do if you get a negative result with a nasal swab after being in contact with someone with COVID-19 or if you test negative and have symptoms? Trust your instinct and retest.

Either take another at-home test a day or so later or if you don’t have time to wait, get a PCR test.

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