When RAT testing for COVID, should you also wipe your throat?

We’re now pretty used to swabbing our noses to test for COVID whenever we have a sore throat or new cough. But should we also be using our rapid antigen test (RAT) to swab our necks, as some social media sources are suggesting?

Because people with omicron infection often get a sore throat early on, they argue that omicron is first found in the throat. Some social media sources say wiping your nose and throat together is more likely to pinpoint an infection.

Sore throats are more common with Omicron than Delta. However, that doesn’t mean you should use your nose rat to dab your throat for Omicron. It is best to follow the instructions on the pack.

Remind me what are the different types of RATs?

There are several ways to test for COVID with a RAT.

Oral samples may include saliva (spit into a tube), saliva from a tongue or cheek swab, or a throat (tonsiloid) swab.

Nose samples can be taken from the front (anterior), middle, or back (nasopharyngeal) of the nose.

There are also many different brands of RAT. Your ability to detect a positive case varies depending on the brand, variant, whether the person has symptoms, and their viral load at the time of the test.



Read more: Doing your first rapid antigen test? 7 tips for an accurate result


What do studies say about RATs for nose vs. throat?

It’s complicated. The time lag between when researchers conduct a study and when it is published means that studies comparing sampling methods were, for the most part, conducted before Omicron or before the widespread use of RATs.

A systematic review of 23 pre-omicron studies found that nose and throat samples tested together were more sensitive (meaning they accurately detected a positive case) than nose samples alone: ​​97% versus 86%.

However, these were swabs that were taken independently (using two separate swabs – one for the nose and one for the throat) and then combined at the time the specimen was tested, rather than taking a combined nose/throat swab (where the nose is wiped). the throat is swabbed with the same swab or vice versa). They also used PCRs instead of RATs.

A study conducted during the Omicron wave tested 49 people with PCR-confirmed COVID who had both nose and throat swabs. It found that 86% of positive cases were detected by nasal swabs on a RAT, compared to 47% by throat swabs and 89% by both methods.

This suggests that omicron is not more easily detectable in the throat. The addition of a throat swab did not result in many additional cases (3%).

Swabbing the throat doesn’t seem to have many additional beneficial effects.
Shutterstock

However, a preprint study, which has yet to be peer-reviewed (reviewed by independent scientists), shows conflicting results.

In this study, 64.5% of the infections were detected with individual nose and throat swabs. But some nose samples tested positive when the throat swab was negative and vice versa. When both tests were performed individually, about 89% of the positive cases were recorded.

When comparing individual nasal swabs to a combined nose/throat swab, the nasal swab captured approximately 68% of the cases, while the combined swab captured approximately 82% of the cases.

In summary, from the two most recent studies that include an Omicron sample, the published study found that nasal swabs were much more effective than throat swabs in detecting COVID. And if the results of both tests were combined, only 3% of the extra cases would be detected.

The (unpublished) preprint study reports conflicting results, suggesting that a combined nasal/throat swab would capture an additional 14% of cases.



Read more: How accurate are rapid antigen tests? Two testing experts explain the latest data


Does omicron appear first or at higher levels in the throat?

A survey found that people with Omicron were 9% more likely to report a sore throat than those with Delta, while the latter were more likely to report a runny nose and sneezing.

However, when comparing saliva from a throat swab to a deep nasal swab in a study of 624 people, researchers found more virus (known as viral load) in the deep nasal swabs than in saliva tests. A test is more likely to detect a positive case when the viral load is higher.

The researchers found more virus in the nasal swab regardless of the day the sample was taken, suggesting the virus is not found earlier in the throat.

Omicron was 4% less likely to detect COVID in throat saliva compared to Delta cases, suggesting that Omicron also does not increase viral load in throat saliva.

However, it’s important to note that the nasal swabs we collect at home are unlikely to be as deep as those used in this study, which could affect the results.

Man looks at RAT test result.
The virus does not seem to appear in the throat first.
Shutterstock

Other things to consider

The type of swab also differs depending on whether it is intended for a nasal or oral test and may not always be appropriate for sampling from a different area due to differences in the shape and flexibility of the swab.

The pH (a measure of acidity) also differs in the throat and nose, and altered pH can affect the COVID test function and therefore potentially affect the result.

So what should you do?

The website of Australia’s regulator, the Therapeutic Goods Administration, recommends doing either a nasal or an oral test, depending on direction.

Likewise the US Food and Drug Administration recommends following RAT instructions closely.

While the UK National Health Service (Britain) website refers to swabs of both the throat and nose, what is used here is a RAT kit that is suitable for both.

As there is currently no clear evidence that Omicron occurs earlier or at higher concentrations in the throat, and RATs have been developed and tested for the specific area sampled, it makes sense to continue to follow the testing instructions.

If you want to swab both areas, it’s best to use two separate tests designed for those areas.



Read more: Can you use rapid antigen tests on children under 2 years old?


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