Research shows that the Omicron variant may be more concentrated in the mouth and upper respiratory tract than other variants. This has led to some questions about the best way to perform rapid at-home tests for the virus. Is a nasal swab good enough, or is it more accurate to swab the throat? Or is it better to combine nasal and throat swabs? The answer is a little more complicated than you might think. We’ll discuss the differences between COVID-19 tests and what the current evidence says about combined nasal and throat testing.
What’s the difference between nasal and throat swab COVID-19 tests?
The key difference between nasal and throat swabs is the bodily fluid that the tests collect. Each collection method checks for the COVID-19 virus in a different location of the upper respiratory tract (nose, throat, and mouth). And many tests are designed for collection from only one specific location.
There are several different ways to test for COVID-19:
- Nasal swabs are generally self-administered, either in your home or at testing sites that allow you to swab yourself.
- Throat swabs, also called “oropharyngeal swabs,” collect a sample from the back of the throat by going through the mouth. Usually a healthcare provider does this.
- Nasopharyngeal swabs go deeper into the nose and collect a sample from the back of the nose or back of the throat. Usually a medical provider performs this swab.
- Saliva swabs use a sample of saliva to test for the COVID-19 virus. This is usually done by swabbing areas of the mouth — like the cheeks.
The rapid antigen tests that most people are using in the U.S. are specifically designed for nasal swabs.
What evidence supports combining different COVID-19 tests?
There’s limited evidence for combining throat and nasal swabs with rapid tests. And it’s mostly based on personal accounts. There have been multiple social media stories of people who test positive on a throat swab after a negative result from a nasal swab. But solid, scientific research investigating these claims is still in the works.
Currently, rapid home tests in the U.S. aren’t designed to test the throat. And this is related to the pH of a saliva specimen. Research shows that when the pH of the sample changes, a rapid COVID-19 test can produce a false-positive result. In fact, even drinking acidic juices or soda close to the time of sample collection can alter the result of a rapid test. And the pH of the mouth is naturally more acidic than the nose. So, the FDA does not recommend combining tests at home until more research is done.
Which COVID test is more accurate, nasal or throat swabs?
There’s ongoing research to determine the most accurate way to test for COVID-19, particularly with the Omicron variant. We do know that Omicron tends to stay in the upper respiratory tract, rather than travel to the lower respiratory tract or lungs. So a throat swab may be more likely to find it. But again, the research is still in progress.
A recently published study suggests that saliva swabs may be more accurate to detect the Omicron variant when compared to nasal swabs. But this study looked at PCR tests, not rapid tests that are done at home. So the results may not be applicable to home testing because these tests work differently. Another study found that PCR throat swabs were just slightly better than nasal swabs in detecting the virus. But this study was done prior to the Omicron variant.
It’s also important to note that throat swabs are more difficult to collect. And if done incorrectly, the result may not be accurate. At this time, it’s best to wait until we have more data, and leave the throat swabs to a provider.
Written by Joanna Jan, MD | Reviewed by Katie E. Golden, MD