Lu Hongzhou said that after the outbreak of the epidemic, large-scale nucleic acid screening for close groups and high-risk groups is an important means for early detection of infected patients. Courtesy of Professor Lu Hongzhou
China News Network, January 27 (Sun Guogen, Chen Jing) The recent new crown pneumonia epidemic has attracted public attention. There are many "questions" about the advantages and disadvantages of "diversified" nucleic acid detection and "antigen detection". On the 27th, the reporter interviewed the experts of the national new coronavirus infection medical treatment group, the experts of the overseas anti-epidemic medical expert group, the doctoral tutor of Fudan University, the president of the Third People's Hospital of Shenzhen, and the famous infectious disease expert Professor Lu Hongzhou.
One. Related nucleic acid testing
Reporter: What is the reason for the nucleic acid test to find that the current round of epidemics in Xi'an and Yuzhou, Henan Province, exceeded 10 rounds?
Lu Hongzhou: After the outbreak of the epidemic, large-scale nucleic acid screening for close groups and high-risk groups is an important means for early detection of infected patients, and nucleic acid testing has played an important role in epidemic prevention and control. But we found that in the past two years of fighting the new crown virus, with the popularity of vaccines and the evolution of the virus itself, the new coronavirus has become "very smart", and its characteristics are constantly undergoing important changes, such as more and more hidden infections of asymptomatic infected people, the spread of the virus is getting stronger and stronger, and some negative cases before the diagnosis of some cases in the screening process are also reported from time to time. In this case, the frequency and scale of screening have been adjusted with the aim of controlling the spread of the outbreak faster and better. Therefore, according to the latest version of the national "diagnosis and treatment plan for novel coronavirus pneumonia", real-time PCR test positive for nucleic acid of new coronavirus is one of the most important indicators for confirmed patients. "Early detection, early diagnosis, early isolation, and early treatment" are important strategies for the prevention and control of the new crown epidemic.
Lu Hongzhou pointed out that each person's immune system has different ability to control the invading pathogen, so there are differences in detoxification laws between individuals. Courtesy of Professor Lu Hongzhou
Reporter: In key populations, such as Shanghai's Aomi Kerong infected people were diagnosed in the last test of 14+7, zhengzhou also has a case of 7 days to do 7 nucleic acids before being diagnosed, why are there continuous false yin results?
Lu Hongzhou: To be precise, this situation is not a false negative result. Because natural immunity is the first line of defense against pathogen infection in the human body, when the body's immune system perceives the invasion of external pathogens, it will respond at the first time to inhibit the replication of pathogenic microorganisms such as viruses or bacteria, and only after breaking through this line of defense can infection be established, and the viral load can only be detected when it reaches a certain level. Each person's immune system's ability to control the invading pathogen is different, so there are differences in detoxification laws between individuals. Now with the popularization of vaccines, most people have added humoral immunity to fight the infection of the virus on the basis of natural immunity, so the time it takes for the virus to establish infection will be longer, which directly affects the diagnosis time of the infected person.
Reporter: In the non-key population, in the daily life of ordinary people, some low-risk groups with high travel frequency are doing nucleic acids almost every day, and accurate to the validity period of 48 hours, and the outpatient and inpatient clinics of medical institutions have also improved the frequency and requirements of detection. Why is nucleic acid testing more and more frequent?
Lu Hongzhou: China's current epidemic prevention policy has effectively controlled the epidemic and spread of the new coronavirus in China. However, due to the widespread existence of the epidemic abroad, the risk of importation of people and imported goods as vectors is persistent. Recent data from the outbreaks in Beijing, Zhuhai and Shenzhen show that confirmed cases may have been infected with the virus through overseas items, and most cases were discovered during routine nucleic acid testing. In addition, nucleic acid testing is a "while-in-progress" test that can only represent the state of health at the time of sampling. When the concentration of virus in the body is not enough or the sampling method is not standardized, it is possible that it will not be detected. Therefore, the current nucleic acid testing policy can maximize the cooperation with the mainland's "dynamic clearance" policy.
Reporter: In many rounds of the epidemic, although the frequency of the entire nucleic acid detection system is getting higher and higher, the detection rate and sensitivity are declining, what is the reason for this phenomenon?
Lu Hongzhou: With the development of nucleic acid detection technology, the sensitivity and specificity of nucleic acid detection kits are getting higher and higher, and the sensitivity of kits of many manufacturers has been significantly improved relative to the initial stage. The so-called missed tests and false negatives in most cases are not caused by the sensitivity of the kit, but mainly due to detoxification differences between individuals and possible sampling quality problems. Our hospital team systematically compared the accuracy of different respiratory samples for nucleic acid testing of the novel coronavirus in the early stage of the epidemic, and the results showed that when collecting samples for nucleic acid detection, sputum collection was given priority, followed by nasal swabs. False-negatives may occur with throat swab samples alone for viral screening. With the continuation of the epidemic, the public's awareness of active prevention and control is constantly improving, in addition to the routine of wearing masks, washing hands frequently, ventilating more, and actively vaccinating, everyone also has a clearer understanding of some high-risk behaviors that may have a risk of infection, and will participate in nucleic acid screening and reporting in a timely manner. This has a very positive effect on us to better control and respond to the outbreak.
Reporter: On the 15th, the National New Crown Epidemic Prevention and Control Command issued a document requiring the promotion of nucleic acid testing of 20 mixed 1, from single inspection, to 5 mixed 1, 10 mixed 1 and then to 20 mixed 1, why is it more and more mixed, what are the advantages and disadvantages of doing so?
Lu Hongzhou: Mixed testing is the best way to significantly improve the efficiency of nucleic acid screening and control costs. The current mixed sampling method is to collect samples from multiple subjects into the same sampling tube, and then extract nucleic acids for the next step of fluorescence quantitative PCR detection. Therefore, from a technical point of view, this does not reduce the sensitivity of nucleic acid screening. With the current increase in the scale and frequency of screening, the main reason for the increase in the number of mixed tests is also to improve the efficiency of screening and control the cost of screening. 20 Mix 1 is more suitable for nucleic acid screening in large-scale populations. Of course, in this process, it also puts forward higher requirements for the update of our mixed sampling tube and the pretreatment of samples by nucleic acid detection personnel before nucleic acid extraction.
Two. Related antigen testing
Reporter: At present, Europe, the United States, Australia, Singapore, Japan and other countries have begun to take antigen detection as the core of the prevention and control strategy, what kind of scientific principles are these strategies based on? What are the necessary support conditions for these countries? What are the risks of such a strategy? What are the reasons for not initiating antigen testing in China?
Lu Hongzhou: Compared with nucleic acid testing, antigen detection has the advantages of convenience, speed and low cost, so that ordinary people can easily achieve home testing. At present, the new coronavirus in Europe, America, Australia, Japan and other regions is still in a large-scale epidemic, limited by manpower, material costs and other factors, nucleic acid detection capacity can not meet the needs of epidemic prevention and control; in addition, foreign control measures for new coronavirus patients are mainly home isolation, so antigen detection has become their main means of detection. Although the application of some new technologies in antigen detection reagents has greatly improved the sensitivity, it is still significantly lower than the nucleic acid detection method, and usually only strong positive samples can be detected, with a certain false negative rate. In this case, there must be a case of missed inspection. At present, China's nucleic acid testing capabilities are strong and can meet the needs of the current epidemic prevention and control strategy, so the nucleic acid test results are still subject.
Reporter: In China, where the overall prevalence rate is low, are the results of antigen testing credible or of reference significance? Considering the convenience of antigen detection, is it feasible to assume that the green code population seeks medical treatment, travel, and enters public places on the grounds that the antigen self-test is negative?
Lu Hongzhou: The positive results of reliable antigen detection kits are certainly credible, and the specificity of good reagents is 99%. However, according to the mainland's current prevention and control guidelines, nucleic acid testing is still the gold standard, that is, if the antigen test is positive, nucleic acid testing is still required to confirm; at the same time, limited by the sensitivity of the antigen detection kit, it will inevitably miss some infected people with low viral load. I believe that under the mainland's current epidemic prevention policy, it is not suitable to use the antigen self-test results as a basis for seeking medical treatment, traveling and entering public places.
Reporter: For Ami Kerong, who is mainly mild and has a high rate of family recurrence, does the antigen strategy have an advantage? What complements can antigen detection itself provide for our current nucleic acid-based screening system? Is it necessary to supplement antigen self-testing in China?
Lu Hongzhou: Based on the advantages of antigen detection, self-testing using antigen detection kits can help us quickly find some infected people, and can also reduce the risk of possible exposure during nucleic acid sampling to a certain extent. Due to the limitations of nucleic acid testing capacity in many foreign regions and the control strategies of confirmed patients, antigen testing can provide a good supplement for their epidemic prevention and control. However, based on China's current "dynamic zero clearance" policy and our nucleic acid detection capabilities, there is no need to widely promote antigen self-testing on the mainland at present. If the public feels that there is a risk of exposure and infection, they should go to the relevant institutions for nucleic acid testing in time. Of course, in the future, with the changes in the mainland's epidemic prevention policy, antigen self-testing is very promising as a good supplement to nucleic acid testing. (End)
Source: China News Network