How much do you know about antigen self-tests? The principle and use of antigen detection kits

Date:2022-04-29 0:00:00 Friday

Summary: 01 Antigen testing is suitable for people In March this year, the National Health Commission released the "New Coronavirus Antigen Testing Application Plan" (hereinafter referred to as the "Plan") on its website, stating that it would promote the......

Antigen testing is suitable for people

In March this year, the National Health Commission released the "New Coronavirus Antigen Testing Application Plan" (hereinafter referred to as the "Plan") on its website, stating that it would promote the monitoring mode of "antigen screening and nucleic acid diagnosis", and add antigen testing as a supplement on the basis of cases found in nucleic acid testing. Antigen testing is an immune-based test obtained through a throat swab sampling process that quickly tells a patient whether the virus is present in a patient within 30 minutes. But it should be emphasized that As a supplementary detection method, antigen detection is far less accurate than nucleic acid detection because of its low detection sensitivity.

At the same time, the "Plan" stipulates the applicable groups of antigen testing: first, people who go to primary medical and health institutions for treatment, accompanied by respiratory symptoms, fever and other symptoms, and have symptoms within 5 days; The second is isolation and observation personnel, including home isolation observation, close contact and sub-close contact, entry isolation observation, personnel in closed and controlled areas and control areas; The third is community residents who have antigen self-testing needs.

So, how does antigen detection work? What is the process of using test kits?

The principle of antigen detection kits

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Chinese instrument review

The new crown antigen detection kit belongs to the specific application of lateral immunochromatography, the technical principle of immunochromatography is to fix the specific antibody first in a certain area of the nitrocellulose membrane, when the dry nitrocellulose end is immersed in the sample, due to capillary action, the sample will move forward along the membrane, when moving to the area where the antibody is fixed, the corresponding antigen in the sample is specifically bound to the antibody, if stained with immunocolloidal gold or immunoenzymes can make the area display a certain color, This enables specific immunodiagnosis. According to the different color development materials, the method can be further divided into colloidal gold immunochromatography and latex immunochromatography.Antigen detection kits are based on the specific binding of antigens and antibodies to achieve the purpose of detection.

The sample is added dropwise to the sample pad and the sample liquid flows in the direction shown. When the sample contains a virus, the virus binds to the antibody on the surface of the chromogenic component, and then continues to flow forward to the detection line (T-line) and binds again to the specific antibody fixed on the T-line, and the T-line turns red when the chromosphere is fixed at this position. The excess chromosphere will continue to flow forward through the T line until it reaches the quality control line (C line), where the C line turns red after binding to the coated antibody. Hence we According to the principle of double-antibody sandwich ELISA, when the test kit shows two red lines, we judge it positive, that is, there is virus in the sample.

If the sample does not contain virus, the sample cannot form a "sandwich structure" when flowing through the T-line, cannot bind to the specific antibody fixed on the T-line, and the chromogenic components cannot function so the T-line does not turn red. As the sample continues to flow through the C-line, it binds to the secondary antibody there and develops color, proving that the chromatography process is smooth Only the C-line turns red, and we judge the result to be negative.

Antigen test kit usage process

The use process of the new crown antigen test kit is roughly as follows:

The kit includes a sampling swab, kit, antigen dropper with preservation solution. Take out the sampling swab, take samples in the nasal cavity or throat, place the swab in the sample tube containing the preservation solution, and then add the liquid in the tube to the round hole marked with S in the kit, stand and wait for more than 15 minutes to observe the results. After the inspection is completed, the waste materials are packed into bags and disinfected.

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Planning and production ▏ Lu Zhuangzhou

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