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What is the difference between antigen detection and nucleic acid detection?

March 28, 2022

Recently, several new crown antigen self-test products have been approved for marketing, which has attracted attention.

 

What is an antigen test, and what is the difference from the well-known nucleic acid test? Why add this new detection method? What is the detection accuracy? What does one need to do? Are there any risks? Doubts about this new form of detection emanate.

 

What exactly is an antigen test? How is it different from nucleic acid testing?

 

Antigens are like the "clothes" that the virus wears on the outside, and nucleic acids are the genes inside the virus.

 

These two tests are slightly different. The antigen test is a method that starts from the antibody to measure the "clothes", and after the comprehensive specificity, the virus can be displayed; while the nucleic acid test is more complex and requires amplification to complete, because with the amplification link, the sensitivity of the nucleic acid test will be higher, but the corresponding time required to obtain the results is longer.It will be difficult if the detection speed only relies on nucleic acids. Because the nucleic acids need to borrow machines, there are very professional systems for sampling requirements and machine amplification. If sampling is inconvenient in this place or there are no suitable conditions for amplification, is there another method? Like a home pregnancy test stick to detect pregnancy, the antigen test can be used at home, and the speed is fast. It can also be used in hospitals with poor conditions, and the cost is relatively low. At present, the detection methods of the new coronavirus are mainly nucleic acid detection and antibody detection. AllTest China adopts the antibody colloidal gold method and has successfully developed a new coronavirus (COVID-19) IgG/IgM antibody detection kit.

 

The accuracy and sensitivity of antigen detection are lower than nucleic acid detection, and nucleic acid detection is still the "gold standard" for new crown detection. Antigen testing has its advantages. One of them is that it is convenient and does not require a machine. You can use it at home and get the results in a short time. Nucleic acid testing involves multiple processing steps, and it takes about 4-6 hours to produce results.

 

How accurate is the antigen test?

 

The sensitivity of antigen detection reagents is 75%-98%, and the specificity is between 95%-99%.

 

Who needs to do antigen self-testing?

 

People who go to a medical institution for treatment and have symptoms like fever, and others who have symptoms within five days. People like quarantine observation personnel, including home quarantine observation, close contact, sub-close contact, entry isolation observation, closed area, and control area personnel. These are the ones who need antigen self-testing. Qualified groups are people who think they are at a higher risk of infection.

 

What are the precautions for antigen self-testing?

It is not difficult to see from the instructions of the pre-sold antigen self-detection product that its use is similar to a home pregnancy test strip. When self-testing and sampling, you should be a little "hard" on yourself, "because you need to scrape off a part of the epithelial cells in the throat or nasal cavity to detect whether there is a virus." After the test, you should properly dispose of the test supplies. A positive antigen test corresponds to the time when an infected person is highly contagious. Therefore, once the antigen test is positive, for you and your family's safety, don't go anywhere.

 

Why is this detection method so good? Has everyone used nucleic acid detection before?

Everything has its two sides. Omicron spreads widely in a short time. According to the requirements of epidemiological prevention and control, it is recommended to quickly find the source of the infection, and it needs more simple and easy to promote detection technology to adapt to the current situation. Epidemiological characteristics of this strain, so large-scale rapid testing should be carried out in a larger population. Antigen detection is a complement to existing nucleic acid detection methods. Given the characteristics and current situation of antibody detection reagents, there are certain limitations in sensitivity and specificity, which cannot be used as the only basis for the diagnosis. The exclusion of new coronary pneumonia can only be used as a supplement to existing viral nucleic acid detection reagents. Antigen tests are slightly less sensitive because they do not have amplification, but once they are positive, they are highly valuable.