Drinking cola, orange juice will cause a positive antigen test? Professional answers are coming

Recently, it has been rumored on the Internet that when antigens are detected, the use of cola or orange juice will cause the antigen detection reagent to be weakly positive. According to the pictures transmitted on the Internet, the label is dripped into the antigen reagent with the word Cola, and a very faint yellow horizontal bar appears in the lower T position. Otherwise, reagents that dripped into other liquids all showed normal. Another online video shows false positives when using orange juice to drip antigen reagents.

A study published in MedRxiv, a clinical medical database jointly established by Yale University and Cold Spring Harbor Laboratory, also showed that:

Sodas, energy drinks, or alcoholic beverages (vodka and whiskey) can make people test positive for COVID-19 antigens without COVID-19.

The study data showed that one sample (1/14; 7%) of the spring water produced a negative result. Ten beverages (10/14; 71%) produced positive or weakly positive results. Three samples (3/14; 21%) produced invalid results, of which, mainly fruit juice drink concentrates. There was no clear correlation between the pH of the beverage (pH 5.0 in 13/14, 6.5%; 7% in 1/14) or the sugar content of the beverage (range 0-10.7 g/100 ml) and its positive result. All 4 artificial sweeteners produced negative results.

The study states:

This is not because of the poor quality of the COVID-19 tester, but because the acid in the soft drink may react and make the result positive.

In the Shanghai network platform to debunk the rumors, Wang Ying, a professor at the Shanghai Institute of Immunology of Shanghai Jiao Tong University School of Medicine, said that cola as a common beverage, its composition is complex, if directly poured into the extraction tube containing the preservation solution, and this mixture is added to the sample hole of the test card, with the diffusion of the liquid, it is possible to make structural changes in the antibodies at the T and C positions, thus showing other color bands that are not used for colloidal gold purple, and the obtained bands have no significance of result determination.

Jin Dongyan, a virologist at the University of Hong Kong, told reporters that the principle of antigen testing and pregnancy testing is the same. From the perspective of the structure of the antigen detection reagent, the reagent is composed of two parts, the control part of the control part and the sample part, that is, the control part of the reagent itself contains positive components. The use of improper means for antigen detection can easily destroy the internal structure of the reagent, resulting in mixing the control part with the sample part, resulting in false positives.

Jin Dongyan said that the conclusions drawn through the above phenomenon are not scientific and meaningless, and antigen reagents should be correctly used according to the instructions. At present, the antigen detection reagents that have passed the domestic approval and certification can meet the testing standards and do not need to worry too much.

Since the national open antigen testing. Up to now, the State Food and Drug Administration has approved 27 new coronavirus antigen detection reagent products. Among them, there are 19 types of colloidal gold methods, which are from Wanfu Biology, Nuoweizan, etc.; there are 5 latex methods, which are from Lizhu Group, Beijing Jinwolf and so on. There are 3 types of fluorescent immunochromatography methods, which are from BGI, Beijing Huaketai and Shenzhen Biology.

For the new crown antigen reagents of different technical routes, the relevant manufacturers also analyzed the above situation.

Take the latex method as an example. On April 14, the relevant person in charge of Lizhu Group told reporters that orange juice and other liquids such as juice, soy sauce, and other carbonated drinks are complex, and have a certain acidity and alkalinity, and may dye or react with biological raw materials on the "T line" and "C line", or destroy the marker (especially the marker of non-covalent link), and it is meaningless to drop them directly into the reagent card.

The above-mentioned person in charge said that any tool has special attributes, and the new crown antigen detection card is a test tool that specifically detects whether a person is infected with the new coronavirus and must be used in a targeted manner.

The relevant person in charge of Livzon Group also said that The new crown antigen detection kit of Livzon uses colored latex microspheres as a signal marker, and the latex microspheres have a uniform particle size and are 5-10 times larger than conventional colloidal gold particles, and the detection sensitivity has been improved. Colored latex microspheres are synthesized with activated groups such as carboxyl groups, and the labeled antibody and latex are covalently linked by chemical bonds, which is more stable than the charge connection between colloidal gold and protein. Therefore, the probability of false positives in the aforementioned scenarios is low.

At present, there are three methods of the new crown antigen self-testing agent: fluorescence chromatography, colloidal gold method and latex method, of which the fluorescence chromatography method requires professional equipment, and extensive self-testing is difficult; Lizhu's self-testing antigen reagent uses latex method. The colloidal gold method and the latex method do not require instruments to detect themselves; compared with the colloidal gold method and the latex method, the results of the latex method are clearer and the results are more stable. The fluorescence immunochromatography method requires additional equipment to cooperate with interpretation.

Take the colloidal gold method as an example. On April 14, the relevant person in charge of a colloidal gold antigen approved company told reporters that antibodies (professionally known as double antibody sandwich method) need to be used in antigen detection, and antibodies are essentially proteins. Because proteins have a specific range of active PH, when the solution environment in which it is located changes, such as encountering acid, 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.) is dripped into the dosing well, the antibodies in the reagent may directly produce a large amount of aggregation and do not move (manifested as a blank piece of the result reading area), or together with the T/C line antibody in the result reading area, they will accumulate and precipitate color, forming a false positive phenomenon.

And in terms of fluorescence immunochromatography. The relevant person in charge of BGI Gene told reporters that BGI's new crown antigen detection kit adopts fluorescence immunochromatography method, fluorescence quantitative immunochromatography products use functional nanospheres as the carrier technology, combined with fluorescent marker probes, high luminescence stability, and the instrument directly detects excitation fluorescence signals instead of the CCD surface optical density scanning technology used in traditional gold scale quantification. The heartbeat has a higher signal-to-noise ratio, higher signal detection volume, and detection sensitivity. Therefore, the probability of false positives in the above cases is low.

Source of this article: Interface News