Buzz
At-home rapid COVID-19 tests typically guide you to insert a cotton swab into each nostril and place it in a testing tube or card. However, some individuals have shared images on social media, showing a negative nasal test result alongside a positive throat swab result. Some experts suggest that throat swabs might be more effective in detecting early-stage infections. The reality is more complex than that.
The tests available for at-home use were only validated for nasal samples. If they are proven to detect COVID accurately in throat swabs, that would be fantastic—but we don’t yet know if we can trust those results. To learn more about the throat swab situation, I reached out to Susan Butler-Wu, a clinical microbiologist at the University of Southern California, specializing in infectious disease testing.
According to Butler-Wu, a throat swab can be correct on occasion, but the question is: how often is it wrong? The only way to determine this is through studies comparing the new method of testing with other available tests. As Butler-Wu explains, “In the lab, when we develop a new test, we don’t immediately use it. It must be validated to ensure it works and that no external factors affect the results.”
The details are crucial
Tests can yield inaccurate results if used in ways they weren't meant for. For instance, students discovered that cola and fruit juice can manipulate rapid tests into showing a “positive” result.
If you had a Coke right before your throat swab, could that impact the outcome? Possibly! It's also possible that the natural cells or compounds in your throat could react differently in the test than the ones found in your nose. We don’t have enough data to draw a definitive conclusion. Maybe throat swabs are more reliable—that's a possibility!—but they could also be less reliable.
Rapid tests originally used nasal swabs because early data showed they were more likely to detect the virus. This could have changed with Omicron, and some initial data suggests it has, but it's too early to revise our testing protocols. (And don't forget, Omicron isn't the only variant in circulation.)
Tests can vary significantly by brand in terms of their sensitivity and the exact chemistry used to detect the virus. So, even if one brand works well with throat swabs, it doesn’t mean the same will hold true for all brands.
Here’s another factor to consider: We're currently experiencing a COVID surge. If throat swabs are prone to false positives—though we're not entirely sure about this—those false positives might be overshadowed by the overwhelming number of true positives. Everyone’s testing positive during a surge! However, once the surge is over, any given positive result would be more likely to be a false positive. (This may sound confusing, but we’ve got an explainer on the topic here. While it covers a different type of test, the principle is the same.) Therefore, it might not be wise to draw conclusions based on recent anecdotes and expect future tests to behave the same way.
So, what should you do?
I reached out to several rapid test manufacturers and received brief responses indicating that their tests are only authorized by the FDA for nasal samples. As expected, the FDA holds the position that tests should only be used as they are authorized, regardless of how promising the idea of using a throat swab might seem. Abbott, the company behind the BinaxNOW tests, which were frequently seen in social media comparisons of nose and throat samples, emphasized in their reply that 'To help ensure accurate test results, it is crucial to follow the instructions for use.'
Butler-Wu advises that if you choose to use a throat swab—or a combined nose-and-throat swab—it’s important to recognize that the results may not be entirely accurate. If the test shows a positive result, she recommends seeking confirmatory testing, but also assuming you have COVID until the results come in. Similarly, if the test result is negative, don’t assume you’re safe; rapid tests often miss many genuine infections, especially in the early stages.
Additionally, it's important to note that consuming food or drink can potentially influence the results of a throat swab. While no studies have determined the exact amount of cola needed to impact the test, throat-swab test instructions (for other testing protocols) generally advise not eating or drinking for at least 30 minutes before taking the sample.
"The problem is, we can't base recommendations on personal stories," Butler-Wu explained to me. "There’s simply not enough data to determine how trustworthy throat swabs are." Therefore, if you decide to use one, you should be aware of its limitations.
