Coke and orange juice tested positive for COVID-19 virus?

Can't drink coke or orange juice before antigen testing?

Can't drink coke or orange juice before antigen testing? Recently, there have been frequent "experimental" videos related to the antigen detection kit on social platforms: dropping cola into the kit and finding that the cola antigen test is "positive". Can't you drink coke or orange juice before antigen testing?

Can't drink coke or orange juice before antigen testing? Recently, it was circulated on 1 Internet that using cola or orange juice will lead to weak positive antigen detection reagent. From the pictures on the Internet, a very pale yellow stripe appears at the lower T position when the antigen reagent marked with the word cola is dripped. At other times, the reagent drops into other liquids and it shows normal. Another online video shows that orange juice dripping with antigen reagent will also appear false positive.

A study published by MedRxiv, a clinical medical database jointly established by Yale University and Cold Spring Harbor Laboratory, also shows that soft drinks, energy drinks or alcoholic drinks (vodka and whisky) may make people test positive for COVID-19 antigen without being infected with COVID-19.

The research data show that a sample (114; 7%) spring water produced negative results. Ten kinds of drinks (10/14; 7 1%) produced positive or weakly positive results. Three samples (3/14; 2 1%) produced invalid results, mainly concentrated juice drinks. The pH value of the beverage (pH 5.0 is in 13/ 14, 93%; PH 6.5 is in114; 7%) or the sugar content of the beverage (range 0- 10.7g/ 100ml) had no obvious correlation with its positive results. All four artificial sweeteners produced negative results.

It is pointed out that this situation is not because of the poor quality of COVID-19 detector, but because the acid substances in soft drinks may react, making the results positive.

Wang Ying, a professor at Shanghai Institute of Immunology, School of Medicine, Shanghai Jiaotong University, said that cola, as a common beverage, has complex ingredients. If it is directly poured into the extraction tube containing the preservation solution and this mixed solution is added to the sample hole of the test card, with the diffusion of the liquid, the antibodies at T and C may change in structure, thus showing other color bands that colloidal gold purple does not have, and the obtained bands are meaningless for judging the results.

Jin Dongyan, a virologist at the University of Hong Kong, told Interface News that the principle of antigen testing is the same as that of pregnancy testing. From the structure of antigen detection reagent, the reagent consists of two parts: the control part and the sample part, that is, the control part of the reagent itself contains positive components. Using incorrect means to detect antigen is easy to destroy the internal structure of the reagent, leading to the mixing of the control part and the sample part, resulting in false positive.

Jin Dongyan said that the conclusion drawn from the above phenomenon is unscientific and meaningless, and the antigen reagent should be used correctly according to the instructions. At present, the antigen detection reagents approved and certified in China can meet the detection standards, so don't worry too much.

Since the national open antigen testing. Up to now, the State Administration of Pharmaceutical Products has approved 27 kinds of COVID-19 antigen detection reagent products. Among them, colloidal gold method is 19, which comes from Wanfu Bio, Novozan, etc. Latex method ***5 models, respectively from Livzon Group and Beijing Jinwowu. There are three rules of fluorescence immunochromatography, which are from Huada Gene, Beijing Huaketai and Shenzhen Bio.

For COVID-19 antigen reagents with different technical routes, relevant manufacturers also analyzed the above situation.

Take the latex method as an example. On April 14, the relevant person in charge of Livzon Group told Interface News that the liquid components such as orange juice, soy sauce and other carbonated drinks are complex and have certain acidity and alkalinity, which may dye or react with the biological materials on the "T line" and "C line", or destroy the markers (especially those linked with non-* * *), and may be directly dropped into the reagent card.

The above-mentioned person in charge said that any tool has special properties, and the COVID-19 antigen test card is a special test tool for detecting whether a person is infected with novel coronavirus, so it must be used in a targeted manner.

The relevant person in charge of Livzon Group also said that Livzon's COVID-19 antigen detection kit uses colored latex microspheres as signal markers, and the particle size of latex microspheres is uniform, which is 5- 10 times larger than that of conventional colloidal gold particles, and the detection sensitivity is improved. In the synthesis of colored latex microspheres, activated groups such as carboxyl groups are added, and the labeled antibody and latex are connected by chemical bonds, which is more stable than the charge connection between colloidal gold and protein. Therefore, the false positive probability of the above situation is low.

At present, there are three methods for COVID-19 antigen self-test reagent: fluorescence chromatography, colloidal gold method and latex method, in which fluorescence chromatography requires professional equipment and a large number of self-tests are difficult; Livzon's self-test antigen reagent adopts latex method. Colloidal gold method and latex method can be detected by themselves without instruments; Compared with colloidal gold method and latex method, latex method has clearer and more stable results. However, fluorescence immunochromatography requires additional interpretation equipment.

Take the colloidal gold method as an example. On April 14, the relevant person in charge of a company that was approved for colloidal gold antigen told Interface News that antibody (professionally called double antibody sandwich method) is needed for antigen detection, and antibody essentially belongs to protein. Because protein has its specific active PH range, when its solution environment changes, such as acidity, it is easy to aggregate and lose its activity.

Therefore, in antigen detection, if an acidic liquid (such as orange juice, lemon juice, cola, etc. ), the antibody in the reagent may aggregate directly without moving (the result reading area is blank), or aggregate and precipitate with the T/C line antibody in the result reading area, forming a false positive phenomenon.

In fluorescence immunochromatography. The relevant person in charge of Huada Gene told the interface journalist that Huada's COVID-19 antigen detection kit uses fluorescence immunochromatography technology, and the fluorescent quantitative immunochromatography products use functionalized nanospheres as carrier technology, combined with fluorescent labeled probes, which has high luminous stability. The instrument directly detects the excitation fluorescence signal, instead of the CCD surface optical density scanning technology used in traditional gold standard quantification.

The detection signal has higher signal-to-noise ratio, higher signal detection quantity and detection sensitivity. Therefore, the false positive probability of the above situation is low.

Can't drink coke or orange juice before antigen testing? Recently, various videos have been circulated on the Internet:

You don't have to poke your nose, just drop the antigen reagent.

After a few minutes, the test results showed negative;

Drip orange juice into that sample adding hole of the slats,

Before long, the "two bars" appeared. ...

People began to doubt whether antigen testing was effective.

How to recognize the test results of the kit?

Look at the authoritative answer again.

The object of antigen detection is human samples.

Biochip experts from Shanghai National Engineering Research Center pointed out that the object of COVID-19 antigen testing should be human samples. Only by following the standard detection process can the accuracy of antigen detection results be guaranteed.

Put down coke or orange juice,

Kit "weakly positive"?

Gao Hengjun, director of Shanghai Biochip National Engineering Research Center, pointed out that the kit used for antigen detection at present uses colloidal gold technology, and colloidal substances are easily destroyed by acidic substances. Coke or orange has a low ph value. Adding samples directly with cola or orange juice will destroy the structure of colloidal gold and may cause false positive results.

However, people eat oranges and drink coke to enter the digestive tract, from the mouth to the esophagus and then to the stomach. Antigen testing is to take samples from nasal mucosa. Eating oranges or drinking coke before the test will not affect the test results.

Drop antigen reagent solution directly.

Even clean water will be negative?

Some citizens did a small experiment, put the cotton swab used for antigen detection directly into the reagent and stirred it, then dropped the reagent into the kit, and soon a red line appeared in the C area of the kit. "Haven't poke your nose, antigen test negative. Does this mean that there is a problem with the antigen detection kit itself? "

In this regard, experts in the field of detection in COVID-19 pointed out that if there is no new coronavirus antigen in the added sample, the detection line in T area will not be colored, and only a red line in C area will indicate a negative result. In fact, the red line in area C is also called the quality control line. Whether the sample contains COVID-19 antigen or not, the antigen detection kit after adding the sample will definitely have a C line. As long as the C light does not develop color, the test result is invalid, so it is necessary to re-test with new test paper or select nucleic acid detection.

Experts remind:

1. Wash your hands and do a good job before testing, and do not use damaged kits to ensure the accuracy of antigen testing results.

2. In antigen detection, the result that the test substance is not standardized and leads to yin or yang does not mean that there is something wrong with the test box itself.

Can't drink coke or orange juice before antigen testing? Recently, there have been frequent "experimental" videos related to the antigen detection kit on social platforms: or dropping cola into the kit and finding that the cola antigen test is "positive"; Change to orange juice, and the result is also "positive"; Others used tap water or dripped preservation solution directly from the extraction tube of the kit and found that the "test" result was "negative" ... Faced with these results, many netizens asked the Shanghai rumor platform: Is the antigen test kit reliable?

The answer to this question is actually very simple: if the antigen test is not carried out according to the product manual, all the results are invalid, which cannot prove that the kit is unreliable.

If you understand the principle of antigen detection kit, it is not difficult to find out why the results of antigen detection with cola, orange juice, tap water or other liquids are not referential:

By observing the kit, it can be found that the C position is far from the sample hole and the T position is close to the sample hole. Among them, the T-site contains a component that can react with the virus antigen in the test solution (the technical term is "anti-specific antibody"), which is called "antibody 1" for short, and is mainly used to judge whether the test solution contains the virus antigen component.

Site C contains a component (also called "specific anti-antibody" in technical terms) that can react with another antibody contained in the test solution, which is called "antibody 2" for short. Antibody 1 is different from antibody 2. When the same liquid sample flows, it either changes color or does not change color.

The test liquid containing human nose swab, throat swab and other components is dripped into the sample hole, and the liquid diffuses. If a purple band is produced at the t position, it means that the test solution contains virus antigen components; If the T- site does not show purple band, it means that the test solution does not contain virus antigen components. When the test solution diffuses to position C again, a purple band will appear under normal circumstances, indicating that the kit is qualified; If there is no purple-red band at the C position, it means that the kit is unqualified and the obtained result is unreliable.

Knowing the principle of antigen detection kit, it is not difficult to know why we should not use coke, orange juice, tap water or any liquid that does not conform to the product instructions: antigen detection kit only reacts to human samples sampled according to the instructions, such as nasal swabs and throat swabs; Other liquids, such as cola and orange juice, are completely different from human samples. They will destroy the components of the test solution in the extraction tube, and any color produced by the reaction after adding the test hole is not referential.

It can be seen that when we use the antigen detection kit, we should sample and detect in strict accordance with the instructions for use, rather than "experiment" with other liquids without authorization. What should not be done is to label those "experiments" without scientific basis as "inaccurate antigen test results" and share them through social platforms.

What's more, although the media and professional organizations have clarified that "the test results of other liquids such as cola and orange juice are meaningless", there are still people who "experiment" with various liquids and spread false conclusions. This is not simply out of curiosity or reminder, but is suspected of deliberately misleading the public and disturbing the order of the exam.

There are hundreds of common liquids, except cola, orange juice, tap water, soy sauce, vinegar, tea and so on. Do you want to do experiments one by one, and then ask professional institutions to refute rumors? This will waste a lot of public resources. In the words on the Internet, people who deliberately conduct such experiments and spread wrong conclusions can be described as "either stupid or bad".

Some netizens suggested to the Shanghai rumor platform that these "experimental" videos may make some inspectors cheat in antigen testing. What should I do? For this issue, the public should not worry too much. Because the result of nucleic acid test is always the "gold standard" to judge whether COVID-19 is infected or not, antigen test is only a rapid screening method and auxiliary means.

More importantly, for the tester personally, only by carrying out antigen testing according to the instructions for use can you accurately understand your physical condition. If you cheat, it is not only irresponsible to others, but also irresponsible to your own health.

Shanghai rumor platform has clarified the incorrect use of antigen test kit for many times. However, in the face of new rumors when changing the liquid, I sincerely hope that relevant netizens will stop using antigen test kit as a tool to spoof or spread rumors, and the video publishing platform should also undertake the responsibility of auditing to prevent such misleading video transmission. Antigen detection according to the standard is an effective means to prevent and control the epidemic situation. I hope everyone will take it seriously and actively cooperate.