Covid-19: compote and coca that are positive for an antigen test, how to explain it? : Current Woman The MAG

As we all know: antigen tests, offered in the face of laboratory congestion and the massive screening strategy put in place, are a little less reliable than PCR tests. But does that mean they are not effective? This is the question many people ask themselves.

Covid-19: a positive antigen test after contact with a soda

On Monday, January 25, a video showing a pharmacist pouring a few drops of Coca-Cola on an antigen test was shared more than 40,000 times on Facebook. In question ? The result of the test: "There you go, the coca test is positive (…) Incredible, unbelievable. I really don't know what to tell you. It's crazy, it's crazy. So how to understand it? I do not know. But hey, at least you know that now ", said the healthcare professional.

This video quickly made the rounds on social networks and was taken up by many people who denounce the ineffectiveness of antigen tests. Contacted by the Agence France Presse, the pharmacist explained that this video was part of a joke. "We were messing around with friends. I did it because many of my patients tell me 'Yes, it seems that if we drink coca we have the Covid' (…) I took the test and I sent it to a group like this and then they had to send it to friends of theirs and it went like this ", he specified to the AFP. As early as January 26, the pharmacist published a correction explaining that this video is only a joke among friends and that it does not affect the reliability of antigen tests.

I strongly recommend this video of some edges that you are ?

Posted by Pierre Sykora on Monday, January 25, 2021

The test used for this "experiment" is an antigen test. Covid-Viro of the French company AAZ. Fabien Larue, CEO of AAZ, explained why the test was positive on contact with Coca-Cola. "It is simply the acidity of the liquid which degrades the test, which destroys its components, and it is this acidity which will induce the non-specific reaction that we see. You can put lemon juice, paint stripper, any acidic solution, it will do the same, it breaks the test", he detailed to the AFP.

"The test must imperatively be used with an extraction reagent (which is not the case in the video), which is provided in the kit and which is essential. It has a crucial role because it balances the pH of the reaction, which guarantees the performance of the test.", added Fabien Larue.

Covid-19: an apple sauce and a soft drink positive for an antigen test

During a session at the European National Parliament on December 10, Michael Schnedlitz also wanted to demonstrate the uselessness of antigenic tests. To do this, he put a drop of Coca-Cola using a swab on the antigen test strip. According to the Austrian MP, the antigen test shows a positive result. He concludes that this type of test is ineffective. The video, posted on Facebook by the MP and on YouTube by his political party, has been viewed by thousands of people in recent days. She is not the only one to have outraged Internet users.

Another video shared on social networks also claims to demonstrate the unreliability of antigen tests. In the latter, a person soaks a swab of applesauce labeled in German and places it on an antigen test strip. "Applesauce has tested positive for coronavirus …", indicates the author of the video in the post caption.

Can a soft drink really test positive for Covid-19?

According to Dialab GMBH, the maker of the antigen test used by Michael Schnedlitz, the Austrian MP did not screen properly. "The sample has not been soaked in a buffer solution. In a properly performed test, the sample is first immersed in a solution which keeps the pH value constant. If you apply the sample (in in this case, Coca-Cola, which has a pH of 2.5) on the strip, as the deputy did, without using the solution in the process, you destroy the antibody protein of the test, which reacts to the virus . (…) The positive mark becomes visible ", detailed in a Facebook post on Dialab GMBH.

The manufacturer of the product clarified that the antigen test would have been negative if it had been carried out correctly, "as described in the instructions". In order to demonstrate this, Dialab GMBH posted a video on Facebook, in which a person reproduces the experiment with Coca-Cola, but does not forget to immerse the swab in a buffer solution. "The result is negative, as you can see in the video. These tests should always be performed by hospital staff or by persons trained to avoid such results and representations.", said the manufacturer.

Covid-19: how to explain that the antigen test showed a positive result for applesauce?

The antigenic test used to test applesauce is that of the company MEDsan. It works like a pregnancy test. Clearly, if two bars are visible at the letter C and the letter T, the result is positive. On the other hand, if a single band appears only at the level of the letter C, the result is negative. If a line is drawn at the level of the letter T, it indicates that the test is invalid.

Unlike the Austrian MP, the author of the video did not forget to dilute the extracted substance in a buffer solution. But did he interpret the result correctly? The individual captioned the dessert is positive for Covid-19. However, some internet users noticed while watching the video that only one bar is visible at the level of the letter C, which means that the result is negative.

Others have observed a slight line at the level of the letter T. "The intensity of the color of the test line (T) may vary depending on the concentration of antigens present in the sample. Therefore, any shade of color of the test line (T) should be considered positive ", can we read in the instructions of the company MEDsan.

The manufacturer explained to France 24 observers that the result perceptible in the video is indeed positive. After being contacted by the AFP, the company carried out its own experiments to try to achieve this result. According to the agency, two employees tested an alcohol-based disinfectant, strawberry jam, window cleaner, apples and apple juice. The disinfectant tested positive for Covid-19. The antigen test also showed a weak positive result for strawberry jam, as for applesauce.

According to MEDsan, these results do not call into question the effectiveness and reliability of antigenic tests. "Our task is to make sure that the test provides reliable results in humans. Applying it to food products does not mean that there is doubt about its validity for detecting Sars-CoV-2", explained to the AFP the MEDsan company.

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