Original title: Hu Bijie: Antigen testing is usually done with nasal swabs, which can be self-tested anytime, anywhere
March 11 news on the website of the National Health Commission, the State Council responded The Comprehensive Team of the Joint Prevention and Control Mechanism for the Novel Coronavirus Pneumonia Epidemic Situation issued a notice, deciding to add antigen testing as a supplement on the basis of nucleic acid testing, and organized the formulation of the “New Coronavirus Antigen Testing Application Plan (Trial)”.
According to the plan, community residents who have self-test needs can purchase antigen test reagents for self-test through retail pharmacies, online sales platforms and other channels. On March 12, the State Food and Drug Administration issued a notice approving the official launch of five new coronavirus antigen self-test products.
What is the difference between antigen testing and nucleic acid testing? How accurate is antigen detection, can it replace nucleic acid detection? Which scenarios are suitable for antigen detection? On March 12, a reporter from The Paper (www.thepaper.cn) interviewed Professor Hu Bijie, a member of the National New Coronavirus Pneumonia Medical Treatment Expert Group and director of the Department of Infectious Diseases of Zhongshan Hospital Affiliated to Fudan University.
Nucleic acid detection is the “gold standard”, and antigen detection is more convenient
Hu Bijie said that in general, nucleic acid detection is still the “gold standard” for new coronavirus infection. The gold standard” is more accurate; while antigen testing is a valuable addition and more convenient.
Nucleic acid detection applies the principles of molecular biology, through reverse transcription, amplification and quantitative detection of the nucleic acid sequence of pathogens, the virus detection sensitivity and specificity are higher, and the accuracy is also higher. Antigen detection uses immunological principles to complete virus detection in a non-laboratory environment quickly. It is an effective supplement to nucleic acid detection, but not a replacement.
“For example, if the positive rate of nucleic acid testing is 100%, then the detection rate of antigen testing is about 70%.” Hu Bijie said.
However, compared with antigen testing, nucleic acid testing is also more expensive. Professional equipment, places, and technicians are required, and the detection takes a relatively long time, at least one or two hours, usually 4-5 hours. The antigen test can be self-tested anytime, anywhere, and the results can be obtained quickly.
“The biggest advantage of antigen testing is its simplicity and lower cost.” Hu Bijie said that antigen testing usually also uses nasal swab sampling. After residents buy it from the pharmacy, they can test it at home.
Hu Bijie said that if the patient has just been infected with the new coronavirus, it may not be detected by antigen testing. After infection with the new coronavirus, when the virus is in the incubation period or early stage, the positive rate of antigen testing is much lower than that of nucleic acid testing. As the patient develops symptoms, the positive rate of the antigen test will increase.
“For example, now we are screening close contact and sub-close contact very quickly. We can screen positive patients who are in the incubation period through nucleic acid testing. Antigen testing may be a few days later.” He said.
He emphasized that this also means that antigen testing is meaningful for screening new coronavirus infections with high viral loads. “A positive antigen test is usually a person with a high viral load and high infectiousness. These people need to take timely measures and undergo nucleic acid testing again for confirmation.”
Antigen As a supplementary method, testing can be used to screen specific populations.
Hu Bijie said that in China, medical institutions basically have nucleic acid detection capabilities in first-tier cities, prefecture-level cities, and county-level cities. Therefore, more accurate nucleic acid detection is given priority.
However, antigen detection has its application scenarios and value.
Hu Bijie listed, first of all, if it is inconvenient to do nucleic acid detection in very remote places, or even do not have the ability to detect nucleic acid, you can choose antigen detection.
Secondly, antigen testing can better meet the needs of residents who are willing to test as much as possible. In normal life, if residents have a little headache and brain fever, and are worried about whether it may be the new coronavirus, they can use antigen detection reagents. Or when there are many people queuing in medical institutions and it is inconvenient to test, you can also perform antigen self-testing first.
It should be noted that if the antigen self-test is positive, regardless of whether there are symptoms of respiratory tract, fever, etc., residents should immediately report to the community (village) where they live, and the community (village) will contact the emergency center according to the new coronary pneumonia. Guidelines for the transfer of epidemic-related personnel, transferring residents to medical institutions with fever clinics for nucleic acid testing.
In addition, with the ability of epidemiological investigation stronger, close contact, sub-close contact, and risk groups can be quickly found. Hu Bijie said that during the period of isolation and observation, in addition to regular nucleic acid tests, quarantine personnel can do antigen self-tests once a day as an effective supplement.