Jul 05, 2021 12:33:00

It turns out that the new corona test can obtain false positive results using cola and orange juice, and what is the countermeasure?

Testing methods for the new coronavirus infection (COVID-19)

include PCR testing, antigen testing, and antibody testing. Among such multiple types of tests, it was found that tests using immunochromatography , which can quickly confirm test results, can disguise positive reactions using soft drinks such as cola and orange juice.

COVID-19: kids are using soft drinks to fake positive tests – I've worked out the science and how to spot it
https://theconversation.com/covid-19-kids-are-using-soft-drinks-to-fake-positive-tests-ive-worked-out-the-science-and-how-to-spot-it- 163739

The image below shows the reaction when cola (top) and orange juice (bottom) are added to a test kit using the immunochromatographic method. Checking the image, you can see that both the test line (T) and the control line (C) are stained red in both soft drink drip kits, indicating a positive COVID-19 test result. In addition, only the control line is stained if it does not originally contain virus.

The mechanism of the above test kit is explained in the following movie.

Lateral Flow Test Teardown-YouTube


When the test kit is disassembled, it contains a filament that easily penetrates the reagent. Of this filament, the colored part is ``antibody labeled with colored particles such as gold colloid (labeled antibody) '', the test line is ``antibody that binds to ``labeled antibody bound to the new coronavirus'', and the control line is coated with an 'antibody that binds to the labeled antibody'.

The inspection mechanism is as follows. First, the sample obtained from the test subject is dripped into the kit.

Antigens such as viruses contained in the sample bind to the labeled antibody as the dropped sample permeates.

When the permeated sample reaches the test line, if the sample contains the new coronavirus, the ``labeled antibody bound to the new coronavirus'' binds to the antibody that coats the test line and stains it red.

And in the control line, the conjugated antibody and the antibody coating the control line bind and stain red.

How to actually use the test kit is as follows. First, when dropping the sample ......

The sample quickly permeates the filament.

If you check the test kit after the sample has penetrated, the test line is not stained and only the control line is stained, so you can see that the sample dropped this time does not contain the new coronavirus. However, if you drop a soft drink such as cola or orange juice as a sample, the test line will also be stained as mentioned above, and the result will be that you are ``infected with the new coronavirus.''

According to Mark Roach, a chemistry researcher at

the University of Hull in England, soft drinks such as cola and orange juice are strongly acidic, with a hydrogen ion index (pH) of 2.5 to 4 due to the phosphoric acid and citric acid contained in them. It is said that it shows It is also known that antibodies are generally neutral and change their structure when they are acidified or alkaline. For these reasons, Mr. Roach said, ``When exposed to an acidic soft drink, the protein structure of the antibody changes. Normally, the protein tries to bind to other substances, so the antibody with the changed structure binds to colloidal gold. and the test line would be stained red.'

In addition, Mr. Roach has also devised countermeasures against test result camouflage using soft drinks. According to Mr. Roach, antibodies that have a structure in an acidic environment will return to their original structure when the environment becomes neutral. Therefore, by washing the filament of the test kit disguised as a soft drink with a buffer solution , the original test results can be confirmed.

The image below shows a test kit with drop of cola on the top, and a test kit with buffer washed after dropping cola on the bottom. When checking the image, both the test line and the control line are stained red in the cola-dropped test kit, but only the control line is stained in the buffer-washed test kit, indicating the original test result. I understand.

The fact that the results of the new coronavirus test can be disguised using soft drinks is spreading among children who want to skip school through SNS. Roach said, ``I found a way to neutralize the tricks of children . I recommend it,' he said.