Home quick tests for COVID-19 instruct you to touch a cotton swab inside each nostril before sliding the swab into its small test tube or card. But some people have posted pictures on social media comparing a negative nose graft at home to a positive one at home throat grafting, and even some experts say that throat grafting is more likely to catch an early infection. But the real story is a little more complicated.
You see, the home tests were only validated for nose samples. If they prove to be able to reliably detect COVID virus in pharyngeal samples, that would be great – but we do not yet know if we can trust these results. To understand what’s going on with the sore throat situation, I called Susan Butler-Wu, a clinical microbiologist at the University of Southern California, whose work focuses on tests for infectious diseases.
A neck graft, Butler-Wu says, “will be really something of the time; but what percentage of the time is it wrong?” The only way to know that would be to do a study that compares this new way of testing with the results you get from other tests. ”In the lab, when we come up with a new test, we do not just start using it We must validate it and make sure that it works and that there are no disturbing substances. “
The concrete means something
Tests can give unreliable results when you use them in a different way than they are designed to handle. The students found out, for example cola and fruit juices can trick quick tests to deliver a “positive” result.
If you drank a Coke just before you took your throat test, could that reveal the results? Maybe! It is also possible that the cells or chemical compounds that are naturally present in your throat may behave differently in the test than those in your nose. We do not have enough data to say for sure. Maybe the throat samples more reliable – it’s possible! – but it is also possible that they are less reliable.
Just because a bunch of people have posted their throat and nose samples to TikTok and Twitter does not mean that the scientific community has seen enough evidence to conclude that throat samples are your best bet. “We can not practice laboratory medicine by anecdotes,” Butler-Wu says. “We need data.”
The reason rapid tests began using nasal swabs instead of throat swabs in the first place was that earlier in the pandemic, data comparing the two found that the nasal swabs were more likely to catch the virus. That may have changed with Omicron, and some early data suggests that it has, but it’s too early to conclude that we need to change our test protocols. (And remember, Omicron is not the only variant out there.)
Tests also differ from brand to brand in how sensitive they are and in the exact chemistry they use to detect the virus. So even though a test mark would prove to be quite reliable when used with throat swabs, it does not guarantee that the same would be the case for others.
And another complicating factor: We have a COVID increase right now. If it was likely that throat swabs would produce false positives – which we again do not know for sure – they would be overwhelmed by all the genuine positive. You are positive, I am positive, everyone is positive! But later, when the increase is over, any given positive will be more likely to be one False positive. (If this sounds confusing, we have a little explanation here. It’s about a different type of test, but the underlying problem is the same.) So it may not be a good idea to draw conclusions from recent anecdotes and expect everything to behave the same way in the future.
So what should you do?
I wrote to a couple of the manufacturers of quick tests, and got short answers back, pointing out that their tests are only FDA approved for nose samples. As you might expect, the FDA itself has taken a position that tests should only be used as approved, no matter how promising the neck grafting situation may look. Abbott, the maker of the BinaxNOW tests that I saw in so many posts on social media comparing nose and throat tests, said in their email that “To help ensure accurate test results, [it] it is important to follow the instructions for use. “
Butler-Wu says so if If you are performing a throat swab or a combined nose-and-throat swab, it is important to understand that the results may not be accurate. If your test is positive, she says, “I would seek affirmative testing, but assume I have COVID until I get the test back.” Likewise, if your test is negative, you should not assume that you are in the clear; quick tests miss a lot of real infections, especially early.
In addition, be aware that things you eat and drink can potentially affect the results of a throat swab. Since no one has done a study on exactly how much cola you need to drink to throw a test, the throat swab test instructions (found for other test protocols) typically ask you not to eat or drink for at least 30 minutes before taking your cotton swab.
“The problem is that we can not base recommendations on anecdotes,” Butler-Wu told me. There just is not enough data to know how reliable throat samples really are. So if you do choose to do one anyway, you should know these limitations.
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