kids use soft drinks to fake positive tests – i worked on the science and how to spot it

Kids are always going to find clever ways to quit school, and the last trick is to fake a positive COVID-19 Lateral Flow Test (LFT) using carbonated drinks. So how do juice, cola, and sneaky kids trick the tests and is there any way to tell a false positive result from a real one? I tried to find out.

First, I thought it was better to check the claims, so I opened bottles of cola and orange juice, then dropped a few drops directly on the LFTs. Sure enough, a few minutes later, two lines appeared on each test, supposedly indicating the presence of the virus that causes COVID-19.

It’s worth understanding how the tests work. If you open an LFT device, you will find a strip of paper-like material called nitrocellulose and a small red pad, hidden under the plastic casing below the T line. Antibodies that bind to the COVID-19 virus are absorbed. by the red stamp. They’re also attached to gold nanoparticles (tiny particles of gold actually appear red), which allows us to see where the antibodies are on the device. When you perform a test, you mix your sample with a liquid buffer solution, making sure that the sample remains at optimum pH, before you drop it onto the strip.

The fluid absorbs the nitrocellulose strip and picks up the gold and antibodies. These also bind to the virus, if it is present. Higher on the strip, next to the T (for testing), there are more antibodies that bind to the virus. But these antibodies are not free to roam – they are stuck to the nitrocellulose. As the red smear of gold-labeled antibodies passes this second set of antibodies, these also take hold of the virus. The virus then binds to both sets of antibodies – leaving everything, including gold, immobilized in a line next to the T on the device, indicating a positive test.

The gold antibodies that have not bound to the virus continue onto the strip where they encounter a third set of antibodies, not designed to pick up COVID-19, stuck to line C (for control). These trap the remaining gold particles, without having to do so via the virus. This last line is used to indicate that the test worked.

Test acidity

So how can a soft drink cause a red T-line to appear? One possibility is that the drinks contain something that the antibodies recognize and bind to, just like they do with the virus. But it is rather improbable. The reason antibodies are used in tests like these is that they are incredibly picky about what they bind to. There’s all kinds of stuff in the snot and saliva collected by the swabs you take from your nose and mouth, and the antibodies totally ignore that mess of protein, other viruses, and leftovers from your breakfast. Thus, they will not react to the ingredients of a carbonated drink.

A much more likely explanation is that something in the drink affects the function of antibodies. A range of liquids, from fruit juice to cola, have been used to trick the tests, but they all have one thing in common – they’re very acidic. The citric acid in orange juice, phosphoric acid in cola and malic acid in apple juice give these drinks a pH between 2.5 and 4. These are quite difficult conditions for them. antibody, which has evolved to function largely in the bloodstream, with its almost neutral pH. about 7.4.

Maintaining an ideal pH for antibodies is critical to the proper functioning of the test, and that is the job of the liquid buffer solution that you mix your sample with, that comes with the test. The critical role of the tampon is evidenced by the fact that if you mix cola with the tampon – as evidenced by this debunking of an Australian politician’s claim that mass testing is worthless – then LFTs are worthless. behave exactly as you would expect: negative for COVID -19.

Thus, without the buffer, the test antibodies are fully exposed to the acidic pH of the drinks. And this has a dramatic effect on their structure and function. Antibodies are proteins, which are made up of building blocks of amino acids, tied together to form long, linear chains. These chains fold into very specific structures. Even a small change in the chains can have a huge impact on the function of a protein. These structures are maintained by a network of several thousand interactions between the different parts of the protein. For example, the negatively charged parts of a protein will be attracted to positively charged areas.

But under acidic conditions, the protein becomes more and more positively charged. As a result, many of the interactions that hold the protein together are disrupted, the delicate structure of the protein is affected, and it no longer functions properly. In this case, the sensitivity of antibodies to the virus is lost.

Given this, you can expect acidic drinks to result in completely pristine tests. But denatured proteins are sticky beasts. All of those perfectly evolved interactions that would normally hold the protein together are now orphaned and looking for something to bind to. A probable explanation is therefore that the antibodies immobilized on the T line stick directly to the gold particles as they pass, producing the famous false positive result induced by cola.

So is there a way to spot a false positive test? Antibodies (like most proteins) are able to fold and regain their function when they find more favorable conditions. So I tried washing a test that had been dripped with cola with a buffer solution, and of course the antibodies immobilized on the T line returned to their normal function and released the gold particles, revealing the true result. negative of the test.

Children, I applaud your ingenuity, but now that I have found a way to uncover your deception, I suggest you use your cunning to design a series of experiments and test my hypothesis. Then we can publish your results in a peer-reviewed journal.