On December 2, Chengdu, Tianjin, Beijing and other places successively announced that nucleic acid certificate tests would be cancelled. Guangzhou also announced on the same day that people visiting general clinics and emergency departments of medical institutions at all levels can pass with a green health code.
On December 1, after the temporary control areas for epidemic prevention and control were lifted in many districts, the Guangzhou Municipal Health Commission mentioned that different nucleic acid testing strategies should be adopted for different groups of people and encouraged families to prepare their own antigen kits .
Subsequently, some communities began to purchase antigen test kits in groups, and many pharmacies in Guangzhou were out of stock of antigen test kits. On December 2, Ding Li, deputy director and spokesperson of the Guangzhou Municipal Administration for Market Regulation, introduced that Guangzhou is coordinating COVID-19 antigen kit manufacturers to reasonably increase production capacity. The current maximum production capacity of Guangzhou’s COVID-19 antigen kits is approximately 10.5 million doses per day. .
On December 2, the Beijing Municipal Health Commission also issued a document stating that citizens should be the first responsible for their own health, "do a good job in personal protection and health monitoring, and make good use of nucleic acid testing and antigen self-testing." . On December 1, the Beijing Health Commission announced measures to optimize daily medical treatment. It was mentioned that for patients without a 48-hour nucleic acid negative result, a supplementary antigen test will be performed during the triage period, and triage will be carried out based on the test results.
What role will antigen testing play in the future? Who needs antigen testing?
The general population does not need to take antigen tests every day
In March this year, the "New Coronavirus Antigen Detection Application Plan" was promulgated, opening antigen testing to three categories of personnel as a supplement to nucleic acid testing. This includes patients who go to primary medical and health institutions and develop symptoms such as respiratory tract and fever within 5 days of symptoms, quarantined personnel and residents who need antigen self-examination for early detection and early isolation. However, the "Plan" mainly focuses on antigen testing for patients by professional medical institutions and testing personnel, and emphasizes that nucleic acid testing is the first choice.
As early as 2020, some countries in Europe and the United States have used antigen testing as an auxiliary method for nucleic acid testing to screen for new coronavirus infections.
The State Key Laboratory of Virology at Wuhan University has a vivid metaphor, imagining the new coronavirus as an orange, and the viral nucleic acid is the orange flap wrapped by the orange peel and endothelium. Antigen testing determines whether the virus is present by detecting the peel or endothelium of oranges. Nucleic acid testing requires peeling off both the peel and the inner peel of the orange. After exposing the orange flap, it is continuously amplified, that is, the gene fragment carrying the virus is continuously amplified so that it can be detected by the instrument and ultimately determine whether there is viral nucleic acid.
Antigen testing is easy to operate, the results can be obtained quickly in 10 to 20 minutes, and the price is cheap. But compared with nucleic acid testing, the accuracy is lower.
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In March this year, Li Jinming, deputy director of the Clinical Laboratory Center of the National Health Commission, introduced that the sensitivity of the antigen detection reagents approved by the country is between 75% and 98%. time, the specificity is between 95% and 99%. Li Jinming mentioned that antigen testing cannot replace nucleic acid testing. When the antigen test is positive, nucleic acid testing must be used for confirmation.
The U.S. Centers for Disease Control and Prevention also mentioned that antigen testing is not as accurate as nucleic acid testing and may not be able to detect the virus in early stages of infection or in people without symptoms. It is recommended to test for 2 to 3 consecutive days. "Home antigen self-testing" The test is not perfect, but it provides a quick and convenient option to detect whether you are infected with the new coronavirus."
Jin Dongyan, a professor and virology expert at the School of Biomedical Sciences at the University of Hong Kong, pointed out to China News Weekly that currently, about 60% to 75% of all confirmed cases in Hong Kong are discovered through antigen testing. A large-scale study in the United States has shown that after three consecutive antigen tests, its specificity and sensitivity are very close to that of nucleic acid, and about 98% of infected people can be found. “It can be tested every day or every other day, usually 3~ Testing should be conducted at least three times within 5 days."
An unnamed public health expert emphasized that in the early stages of the development of the new coronavirus epidemic, when the number of infected people was not large, nucleic acid testing can quickly screen out infected people. However, when there is widespread social transmission, centralized nucleic acid testing can easily lead to cross-infection, and the risks and benefits are not equal. In contrast, the threshold for antigen testing is low. People can just follow the instructions at home, which can effectively avoid this risk.
Who needs to undergo antigen testing? In what scenarios is antigen testing used?
During the fifth wave of the epidemic in Hong Kong, the SAR government distributed 10 to 20 boxes of antigen testing reagents to each family and required self-testing for three consecutive days. "At that time, quite a few hidden infected people were found at once." Jin Dongyan said. He suggested that in the early stages of a large-scale outbreak, as many antigens as possible should be tested in the first round. On the one hand, antigen testing can produce results quickly, which can improve the efficiency of primary screening, identify potential infected persons, and then identify the entire chain of infection; On the other hand, the cost of antigen testing is lower than that of nucleic acid testing, which can effectively alleviate the financial burden on the grassroots.
Many experts believe that for most ordinary people, there is no need to do antigen testing every day. Antigen tests are mainly used to screen high-risk groups. Jin Dongyan introduced that in Hong Kong, two groups of people need to undergo continuous antigen testing, high-risk and specific groups. High-risk individuals include the elderly and employees of nursing homes, medical staff, and staff on the front lines of quarantine such as quarantine hotel and airport employees. Specific groups are dynamically adjusted based on the high-risk points involved in positive patients, for example, people who have stayed in places related to positive patients for more than two hours, or people who have been delineated near places where sewage sample testing has found extremely high viral loads.
Jin Dongyan believes that in the future, antigens can also be considered as access credentials for specific places such as schools, hospitals, shopping malls, etc. to ensure the necessary operation of society. For example, he said that students in Hong Kong should take antigen tests at home before going to school every day, and medical staff should also take antigen tests before going out to avoid hospital infections. In addition, infected persons or close contacts in the community or on the 7th day of home quarantine will undergo two antigen tests respectively. If the test results are negative for two consecutive days, the quarantine can be released.
In accordance with the 20 regulations on optimizing prevention and control, in areas where no epidemic has occurred, nucleic acid testing of risk positions and key personnel shall be carried out strictly in accordance with the scope determined by the ninth edition of the prevention and control plan, and the scope of nucleic acid testing shall not be expanded. According to the ninth version of the prevention and control plan, after one or more local epidemic cases occur in the jurisdiction, in addition to completing a nucleic acid test for all employees, subsequent nucleic acid sampling can be carried out in key institutions such as schools and nursing homes based on the test results and the risk of epidemic spread. Carry out with a sampling ratio of at least 20% every day.
The aforementioned public health experts told China News Weekly that if full-scale nucleic acid testing is not carried out in the future, from the perspective of discovering transmission chains, a 20% sampling rate will be used for nucleic acid testing in such key places. Testing is “definitely not enough” and should be supplemented by antigen testing, which “is best done every day, or at least 3 to 5 times a week.”
Jin Dongyan explained that antigen and nucleic acid detection are complementary. If the antigen test is positive, nucleic acid will be used to determine the viral load and risk of the infected person, which will be used as an important basis for taking appropriate isolation measures. "Good steel is used on the blade." In addition to continuous antigen testing, Hong Kong also stipulates that high-risk personnel must undergo nucleic acid testing once a week, which is equivalent to "double insurance."
Lu Mengji, a Chinese-German virologist and professor at the Institute of Virology of Essen University School of Medicine, told China News Weekly that the biggest benefit of expanding antigen testing is that it can directly screen out "some super spreaders" and They were isolated in time.
On December 2, Guangzhou announced that people visiting the general doors and emergency departments of hospitals at all levels must have a green health code to pass through. Newly admitted inpatients and their accompanying personnel must present a 24-hour nucleic acid negative certificate to enter. Jin Dongyan analyzed that in comparison, the risk of hospitalization is higher, so the requirements for hospitalization are also high. However, he suggested that more antigens can be tested, supplemented by nucleic acids, to reduce the risk of hospital infection.
“It is not just a medical issue, but a social management issue”
After the promulgation of the “Plan”, since April this year, Shanghai, Hebei and other places have implemented antigen testing as a Supplementary means for nucleic acid testing.
Many interviewed experts mentioned that antigen testing is a general trend and will also help reduce the cost of epidemic prevention. However, in the view of the aforementioned public health experts, if antigen testing is to be implemented, the system and management requirements are higher than nucleic acid testing. He said: "Before, everyone only needed to cooperate with nucleic acid testing, but after antigen testing, who will pay for the testing, whether it can cover all people, and how individuals can accurately report results, etc., all need to be considered."
In In his view, this is not just a medical issue, but a social management issue. At present, Guangzhou only encourages families to prepare their own antigen test kits, but there are no specific requirements for how to implement them.
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After Guangzhou encouraged families to prepare their own antigen test kits, some netizens said on social platforms that nucleic acid testing was previously free, and those who were not suitable for antigen self-testing had to pay for it themselves. On December 2, Guangzhou’s Tianhe, Haizhu and other districts began to launch self-funded nucleic acid convenient sampling points, with a mixed charge of 2.8 yuan per person. Nucleic acid testing services in major hospitals also began to resume self-pay, with a single tube charging 13.5 yuan. In contrast, most antigen detection reagents sell for less than 10 yuan per person.
Jin Dongyan introduced that in Hong Kong, the SAR government will distribute free rapid antigen test kits to the above two categories of high-risk groups. If there are many infected people in a community or building recently, a joint team composed of the University of Hong Kong and the SAR government will also test the nearby sewage. If the virus level in the sewage samples is found to be high, nearby residents and cleaners will be contacted for free. Distribute antigen testing reagents to property managers. The rest need to purchase them at their own expense, and some employers will also provide antigen reagents to their employees for free.
Secondly, whether individuals will accurately report the results of the antigen test is also a question that needs to be considered. "Building a declaration system, ensuring the accuracy of the declaration system, and reviewing antigen reagents to drive inferior manufacturers out of the market requires further exploration by national regulatory authorities." Jin Dongyan told China News Weekly.
Some cities have established reporting platforms. In April, in response to the "Plan", the Guangdong Provincial Health Commission launched the "Guangdong Antigen" mini program to support residents in collecting antigen testing information and reporting results, and cooperated with the local Yue Jian Tong, Guangdong Nucleic Acid Mini Program, electronic health code, etc. connect. In May, Hebei Province launched the “Antigen Report” mini program. The Beijing Municipal Health Big Data and Policy Research Center has also launched the "Beijing Antigen", which allows citizens to upload antigen test results through a mini program.
Jin Dongyan introduced that in Hong Kong, personnel in the aforementioned key places who are found to be positive after daily antigen self-tests can automatically report through the "Rapid Antigen Test Positive Result Declaration System", which is operated by the Center for Health Protection of the Hong Kong Department of Health. Launched in March. In order to encourage people to actively use the system, if residents upload their antigen results to the system to reserve nucleic acid, the government will distribute a free gift package, which includes epidemic prevention guides, Lianhua Qingwen, antipyretics, electronic thermometers, 20 boxes of antigen detection reagents and 20 KN95 masks. Residents who do not use this system to report will need to bear hundreds of yuan in testing costs at their own expense.
He added that in order to further verify the accuracy of antigen testing, Hong Kong will regularly conduct nucleic acid sampling on 10% to 30% of reported antigen-positive patients.
However, the above-mentioned public health experts emphasized that promoting antigen testing and making individuals the first person responsible for health places high demands on social management. In addition, he suggested that if antigen testing is to be implemented, how to implement and supervise it should not be explained by each locality, but should be adjusted and modified in the new coronavirus pneumonia prevention and control plan, which will help local implementation in accordance with unified regulations.
Author: Yang Zhijie Huo Siyi