Recently, the new crown virus antigen self-testing agent box has been sold online and offline. Today, experts from the Guangzhou Municipal Center for Disease Control and Prevention introduced that antigen detection has the advantages of simple operation and rapid results, but because the sensitivity is 100 times to 1000 times lower than that of nucleic acid detection, it is easy to appear "false negative", which cannot be used as the "gold standard" to judge whether it is infected.
Advantages of antigen detection: fast and simple
Limitations: Lower sensitivity than nucleic acid testing not a "gold standard"
Li Kuibiao, deputy director of the Virus immunity department of the Guangzhou Municipal Center for Disease Control and Prevention, introduced that from the detection principle, antigens are like the "clothes" worn outside the virus, and nucleic acid is the gene inside the virus, and the principle of the new crown virus antigen detection method is to detect whether there is a new coronavirus protein in the specimen, compared with the nucleic acid detection method, it has two significant advantages: "One is that the speed is very fast, generally about 15 minutes can see the results." Second, the operation is simple, does not need to be a device, can be used at home or in primary medical institutions, just like using a pregnancy test stick to detect whether pregnant is as simple as. Residents self-test at home If they do not take their own nasopharyngeal swabs, it is also possible to take throat swabs. ”
It should also be noted that antigen testing also has its limitations and is not a substitute for nucleic acid testing. Nucleic acid testing is still the basis for confirming the diagnosis of new crown pneumonia, which is the "gold standard". "The sensitivity of antigen detection is 100 to 1000 times lower than that of nucleic acid detection, so in the early or late stage of the disease, when the viral load in the patient's body is relatively low, the antigen detection method will not detect the protein of the virus, and it is easy to have false negative results." Therefore, whether the antigen test results of the suspected population are positive or negative, further nucleic acid testing should be carried out, and the positive results can be used for early triage and rapid management of the suspected population, but cannot be used as the basis for the diagnosis of the new crown virus infection.
Photo: Photo by Li Bo, reporter of Guangzhou Daily and New Flower City
The casual use of antigen testing is not recommended in the general population
Li Kuibiao said that the "Application Plan for Antigen Detection of the New Coronavirus (Trial)" issued by the National Health Commission on March 11 clearly pointed out that the applicable population for antigen testing includes three categories:
The first type is the person who visits the primary medical and health institutions with symptoms such as respiratory tract and fever and has symptoms within 5 days; the second type of isolation and observation personnel, including home isolation observation, close contact and sub-close connection, entry isolation observation, sealing and control area and control area; the third type is community residents with antigen self-testing needs.
"For individual residents, if you suspect that you have been in contact with infected people, have been to high-risk places, feel uneasy, and feel unwell, you can test at home continuously." He stressed that a single antigen test cannot be used as a basis for judgment. Because the sensitivity of antigen detection is low, a negative test may occur early in the course of the disease, resulting in missed tests, so it is necessary to measure continuously for 5 days.
He also reminded that because the epidemic prevention and control situation in Guangzhou is stable at this stage, the overall positive rate of the population is very low, and the antigen detection method itself may also have occasional false positives, so it is not recommended to use antigen testing casually in the general population that does not belong to the above three categories of people, so as not to cause false positives and waste emergency treatment and medical resources.
At the press conference of the joint prevention and control mechanism of the State Council on March 15, Li Jinming, deputy director of the Clinical Laboratory Center of the National Health Commission, also pointed out that antigen testing should be used for high-risk, high-prevalence cluster infection population testing, and the general population should not do antigen testing at will.
Results need to be reported to the community as soon as possible
What should I do with used antigen kits? Li Kuibiao introduced that after self-testing, if it is a negative result, use the sealed bag that comes with the kit to wrap the kit and dispose of it as ordinary garbage; if there is a positive result, it must be reported to the community at the first time, and the community three-person team will collect nucleic acid at home, if the nucleic acid test result is confirmed to be positive, it will enter the process of management of the infected person, and the used antigen kit will be packed into a sealed bag and transferred to the designated medical institution as a medical waste disposal.
Text, photo/Guangzhou Daily, Xinhuacheng Reporter: Wu Ling Correspondent: Sui WeiJianxuan, Sui Disease Control
Video/Guangzhou Daily Xinhuacheng Reporter: Chen Youzi Correspondent: Sui WeiJianXuan, Sui Disease Control
Guangzhou Daily New Flower City Editor: Wu Wanhong