On March 11, the National Health Commission issued an application plan for antigen detection of the new crown virus, and decided to supplement the antigen test on the basis of nucleic acid testing.
Image source: National Health Commission
The plan specifies in detail the applicable groups for antigen testing, including those who go to primary medical and health institutions for treatment, those with respiratory tract, fever and other symptoms and have symptoms; and isolate observers from community residents who need antigen self-testing.
On March 12, CCTV News reported that the State Food and Drug Administration issued a notice approving the application change of the self-test application of new crown antigen products of Nanjing Novizan, Beijing Jinwolf, Shenzhen Huada Inyuan, Guangzhou Wanfu Biology, and Beijing Huaketai Biology. Since then, five new crown antigen self-test products have been officially launched.
And this is undoubtedly a major change in epidemic prevention and control for the mainland that has been implementing nucleic acid testing – what does this mean? Will grassroots epidemic prevention capacity be strengthened as a result? How will the workload of medical staff change?
What is antigen testing?
The new coronavirus is an RNA virus, which is simply an RNA inside, and then a protein shell on the outside, mainly including four structural proteins: spike protein on the surface (S), membrane protein (M), envelope protein (E) and nucleocapsid protein (N) inside.
What we call nucleic acid testing, according to the Eighth Edition of the COVID-19 Protocol, the criterion for pathogenic examination is that the nucleic acid of the new coronavirus can be detected in the test specimen using RT-PCR and/or NGS methods.
In the samples collected, there are actually very few viral nucleic acids. The purpose of RT-PCR is to amplify trace amounts of specific nucleic acid fragments. In this process of continuous cyclic amplification of nucleic acid fragments, the fewer cycles required to reach the threshold indicate the higher the content of specific nucleic acids in the sample.
The new crown self-test kit uses rapid antigen test, that is, a polyclonal antibody against the new crown virus nuclear capsid protein (NP protein) on the test strip to detect N protein antigen 1 on the surface of the virus particles in the sample.
Compared with nucleic acid detection, the advantages of rapid antigen detection are as follows.
The first is convenience. The Rapid Antigen Test Kit is somewhat similar to a pregnancy test stick, which can be done at home and does not need to rely on complex instruments and equipment like nucleic acid testing.
Image source: Basic requirements and procedures for self-testing of new coronavirus antigens
The second is fast. Nucleic acid detection requires multiple amplification of nucleic acid fragments, and the fastest time is 4 to 6 hours, while rapid antigen detection only takes 10 to 20 minutes to produce results, which can be said to be immediately preferable. (At present, nucleic acid detection also has isothermal amplification technology, which can greatly shorten the detection time, but the detection sensitivity is not enough, and there are not many applications.) ）
Why antigen testing?
The policy interpretation of the new crown virus antigen detection application plan (trial) introduced: nucleic acid testing is still the basis for confirming the diagnosis of new crown virus infection, and antigen testing can be used as a supplementary means for screening specific populations, which is conducive to improving the "early detection" ability. Where primary level medical and health establishments have nucleic acid testing capabilities, nucleic acid testing shall be preferred; those that do not have nucleic acid testing capabilities may conduct antigen testing, and do a good job of medical personnel training and patient communication and guidance.
Isolation observers and community residents conducting antigen testing shall carefully read the instructions and standardize operations, and once the antigen test is positive, they should immediately report to the relevant departments; when necessary, nucleic acid testing should be carried out to confirm.
Dr. Li Tongzeng, Chief Physician of the Department of Infection At Beijing You'an Hospital affiliated to Capital Medical University, said: "Antigen testing has always been used in many countries, including Hong Kong, mainland China, and now the introduction of this program can be said to be a natural success, and it is also a milestone event in epidemic prevention and control. In the present, it is first and foremost available to primary medical institutions, such as community, rural medical institutions, clinics, and even school infirmaries. Its operation is relatively simple, if there is a multi-point sporadic, clustered outbreak, antigen detection can be faster to find infected people, earlier to take isolation measures.
From the perspective of economic benefits, comparing antigen detection and nucleic acid detection, due to the low sensitivity rate of antigen detection, for areas with better epidemic control, the infection rate in the population itself is low, and then choosing such a low-sensitivity detection method as antigen is obviously not cost-effective. But when the epidemic is more serious, when the number of infected people is relatively high in a community or school, it is economically meaningful to use antigen testing."
According to the epidemic information of the National Health Commission on the 12th, at 0-24:00 on March 11, Chinese mainland, 31 provinces (autonomous regions and municipalities directly under the Central Government) and the Xinjiang Production and Construction Corps reported 476 new local cases and 1048 new local asymptomatic infected people.
Biomedical Doctor @Aspirin 42195 Meters told Lilac Garden that in the current epidemic prevention and control, the plan is particularly practical: "At present, some cities such as Jilin City have clustered transmission, so it may not be the best arrangement for everyone to queue up to test in such a situation, because it cannot be measured at once, and many people gather to test will increase the risk of infection and is not safe." In addition, nucleic acid results are relatively slow, and the release of antigen test boxes allows everyone to test themselves, which can know as quickly as possible whether the tester is infectious, and isolate the most infectious patients early.
Antigen testing and nucleic acid testing should be complementary. Nucleic acids and antigens are important tests and have their own most applicable occasions. In places with nucleic acid detection capabilities, such as patients who go to the hospital, then the first choice is nucleic acid. However, if there is no nucleic acid detection capability, such as being far away from the testing point, or if you have fever or cold symptoms in the middle of the night, you can use a more convenient antigen test."
Is there a hidden danger for personal use?
One of the most eye-catching points in this plan is that "community residents who have self-testing needs can purchase antigen testing reagents for self-testing through retail pharmacies, online sales platforms and other channels."
In this printing plan, it is also accompanied by the "Basic Procedures and Requirements for Self-Testing of New Coronavirus Antigens", which provides guidance on the use of methods for individuals.
However, there are still some unknown factors about the impact of individual use of antigen test kits on epidemic prevention and control.
Dr. Li Tong Tsang believes that "when used personally, there may be some problems. For example, if someone buys an antigen test kit and tests positive results, will it be reported and will they actively isolate themselves? These are some of the things that need to be considered by us - he may be worried about this social discrimination, worried about the cost of isolation, but chooses to conceal the report, and even more evades nucleic acid testing and avoids medical treatment.
So in the early stages, I think antigen testing may still have to be mainly in the hands of medical institutions."
In this plan, it is also stipulated that the personnel in the home isolation observation, close connection and sub-close connection, entry isolation observation, sealing and control area and control area shall be organized and managed by the relevant management departments (such as communities, villages and towns, isolation points, etc.). Nucleic acid testing is carried out in accordance with the requirements of the current prevention and control plan during the isolation and observation period, and antigen self-testing is carried out once a day for the first 5 days.
For the antigen test during the isolation observation period, Dr. Li Tongzeng told Lilac Garden: "In fact, we are also worried about this problem, and there may be evasion when used for self-testing. First of all, it is necessary to clarify its supplementary role, and secondly, for the isolation area and the sealing area, the nucleic acid interval may be increased, and the antigen detection will be used during the interval between the two nucleic acids, and finally the nucleic acid will be used as the standard for lifting the isolation."
@Aspirin 42195m believes: "Although it is not mentioned in the current interim plan, it is possible to use antigen testing as a criterion for lifting isolation later." More sensitive nucleic acid testing is currently used, but sometimes patients may no longer have a complete virus and are not contagious, but the virus fragments left in the body may still make the PCR show positive, and some patients may continue to be positive for a long time. In such cases, antigen testing is a more reasonable test method, which can lift the isolation of patients who are not infectious in time. At present, the United Kingdom and the United States and other countries recommend antigen testing to decide whether to end isolation."
Image source: Wen Wei Po
Hokkaido University's master's degree in neuroscience, a senior medical consultant at Sheng Nuo's family, and Weibo Science Popularization V Zhuang Shilihe said: "I think this problem will be encountered and cannot be completely avoided, but we feel that our country should have some means to minimize risks." For example, now we need to register our identity card to buy cold medicine, so the report after the implementation of antigen testing is unlikely to be evaded in the mainland.
I think it might be possible to scan the health code, then scan the QR code on the reagent to achieve personal identity binding, and then you must force the upload of the results to achieve control in this way."
What are the implications?
On the mainland, nucleic acid testing is often applied on a large scale when outbreaks occur.
On September 8, 2021, the Health Commission issued the Guidelines for Printing and Distributing the Implementation of Nucleic Acid Testing for the Novel Coronavirus for All Employees (Second Edition), which stipulates that cities with a population of less than 5 million shall complete the nucleic acid testing task within 2 days, and if necessary, can be guaranteed through overall planning within the province (autonomous region, city). Cities with a population of more than 5 million shall complete the nucleic acid testing task within 3 days, and when necessary, they may apply for national support.
So, can the promotion of antigen testing reduce the workload of nucleic acid testing personnel?
Zhuang Shilihe believes: "According to the notice of the State Council's joint prevention and control, it is a supplementary testing method, and its results cannot be used as a basis for confirming the diagnosis. In our country, it is more of a supplement than an alternative to nucleic acid testing. If the antigen test is positive, it is ultimately reviewed by nucleic acid testing, which also requires the intervention of medical personnel.
In addition, the epidemic situation in the mainland is relatively stable compared with Hong Kong or abroad, and there is not much need to implement large-scale antigen testing in this case."
According to Dr. Li Tong, "For medical workers, the most significant effect of antigen testing may be to reduce work stress. Secondary and tertiary hospitals often face admission, and doctors may determine that they do not have COVID-19 but have fever or respiratory symptoms. According to the current epidemic prevention policy, nucleic acids must be screened first, otherwise doctors must wear protective clothing, and patients cannot enter ordinary dialysis rooms, ICUs and operating rooms. If you encounter an emergency such as maternal, dialysis, or even cardiovascular and cerebrovascular diseases, it can cause delays.
Medical institutions are now required not to delay treatment on the grounds of nucleic acid testing, but when it comes to implementation, there is pressure from hospitalization. If there is an antigen test, if there is an emergency need, the antigen can be done first to reduce the risk.
There are also many primary medical institutions that originally relied on dealing with some daily diseases to maintain their operations, but during the epidemic, they could not treat patients with fever and respiratory symptoms. With antigen testing, it is more convenient for ordinary people to seek medical treatment, and there is also a guarantee for grass-roots medical institutions, and it is not necessary to push patients who need nucleic acid testing to higher-level hospitals, and it will also alleviate many doctor-patient conflicts."
At a press conference held after the closing of the Fifth Session of the 13th National People's Congress on March 11, a reporter asked: After the COVID-19 epidemic has lasted for two years, will China consider making the current dynamic zero epidemic prevention and control policy more sustainable? Is there a roadmap open to the world?
Premier Li Keqiang of the State Council said: "Since the outbreak of the epidemic, I have talked with the heads of international organizations and entrepreneurs of multinational companies, and they all hope to get the necessary exchanges. We have opened a fast track and a green channel to ensure normal production and operation. We will continue to accumulate experience, respond to possible changes in a timely manner, and gradually make the flow of logistics smooth and smooth." (Planner: Leu.)
Title image source: Visual China