Residents can test themselves for COVID-19 antigen! Expert: The suggested price is not more than 20 yuan

Zhongxin Jingwei, March 11 (Wang Yuling) On the 11th, according to the official website of the National Health Commission, the Comprehensive Group of the Joint Prevention and Control Mechanism of the State Council in Response to the Novel Coronavirus Pneumonia issued the "Notice on Printing and Distributing the Application Plan for The Detection of New Coronavirus Antigens (Trial)", showing that after research, it was decided to add antigen detection as a supplement on the basis of nucleic acid testing.

After the plan was announced, the public was generally concerned about whether antigen testing could be tested at home. How accurate is it? How much does the test cost? With these questions in mind, Zhongxin Jingwei interviewed a number of experts in the industry.

"It's time"

According to the "Application Plan for The Detection of Antigens of the New Coronavirus (Trial)" (hereinafter referred to as the Program), the population applicable to antigen testing is mainly in the following three categories: first, those who go to primary medical and health institutions for treatment, accompanied by respiratory tract, fever and other symptoms and have symptoms within 5 days; second, isolate and observe personnel, including home isolation observation, close and sub-close connection, entry isolation observation, sealing and control areas and control areas; third, community residents with antigen self-testing needs.

According to the plan, if community residents have self-testing needs, they can purchase antigen detection reagents for self-testing through retail pharmacies, online sales platforms and other channels.

At the same time, the program points out that antigen detection can be detected in primary medical institutions or self-testing, and the sampling personnel of medical testing need to undergo biosafety training and be familiar with the types of specimens and collection methods, while the home self-test requires subjects to read the instructions, standardize sampling, dosing, etc.

Jin Dongyan, a professor and virologist at the University of Hong Kong School of Medicine, told Zhongxin Jingwei,

The so-called antigen test, that is, the search for the antigen of the virus through a nasopharyngeal swab sample, is similar to the "pregnancy test stick", and the results are produced within about 15 to 20 minutes.

"In the process of fighting the epidemic in Hong Kong, antigen detection and nucleic acid testing have been implemented together, and antigen detection has played a great role, and now more cases are found every day than nucleic acid testing." Jin Dongyan said.

According to China News Network Hong Kong, as of March 6, the Medical Supplies Protection Working Group of the Commerce and Economic Development Bureau of the Hong Kong SAR Government has received more than 23 million rapid antigen test kits. According to the Commerce and Economic Bureau, in addition to some of the above-mentioned rapid antigen test kits reserved for compulsory testing by the whole people, more than 12 million test kits have been distributed to the public, designated high-risk and specific groups through relevant departments and the Hong Kong community anti-epidemic connection (link).

Zhongxin Jingwei noted that many foreign countries have also widely adopted antigen testing, Dongxing Securities previously released a research report that due to the implementation of the rapid testing plan, according to the current population of 330 million in the United States, the monthly demand for new crown antigen testing in the United States will exceed 2 billion people, and the market size is expected to exceed Europe. In addition, the World Health Organization (WHO) has recommended rapid diagnostic tests for antigens as an adjunct to the early diagnosis of COVID-19.

However, Chinese mainland, according to the "Diagnosis and Treatment Plan for Novel Coronavirus Pneumonia (Trial Eighth Revised Edition)", the National Health Commission stipulates that a positive nucleic acid test for the new coronavirus is the primary criterion for confirming the diagnosis of new coronavirus, and the new coronavirus-specific antibody test for those who have not been vaccinated against the new coronavirus is used as the reference basis for diagnosis.

Why is antigen testing introduced at this time? "Now is the time, compared with nucleic acid detection and antibody detection, antigen rapid detection has many advantages such as simple operation, fast and efficient, wide application, low cost, safety and reliability, which can greatly reduce the burden on medical staff and medical and health institutions." Huang Ailong, member of the National Committee of the Chinese People's Political Consultative Conference and president of Chongqing Medical University, said in an interview with Zhongxin Jingwei.

As a member of the National Committee of the Chinese People's Political Consultative Conference, during the two sessions of the National People's Congress in 2022, Huang Ailong brought a proposal on building a normalized epidemic prevention and control model that combines "large-scale rapid detection of antigens based on home self-testing + targeted small-scale precision nucleic acid detection".

Huang Ailong mentioned that since 2021, some areas across the country have carried out large-scale antigen rapid detection emergency drills of "home self-testing", and the effect is no less than nucleic acid testing.

"Taking Chongqing as an example, Chongqing Medical University has carried out drills with Chongqing Bishan District and High-tech Zone, distributed a total of 16,000 antigen rapid detection reagents, collected effective data for 15,022 people, and the 8-hour completion rate was as high as 75.11%; 15,017 people were identified as negative by the self-developed artificial intelligence system, and the consistency with professional and technical personnel review was 99.97%."

What is the accuracy rate?

Previously, some people have questioned the accuracy of antigen detection, believing that compared with nucleic acid testing, antigen detection sensitivity is low, and there are more "false positives" and "false negatives".

In this regard, Jin Dongyan said that on the one hand, in principle, antigen detection can find out that the infection is highly contagious and has the potential to cause super transmission, "For the Ct value (Note: the new coronavirus Ct value can determine whether the patient's test result is positive or negative) For people with 30-45, the antigen test result has a high probability of 'false negative', but these patients are not infectious." For people with Ct values of 25-30, the infectivity is also relatively low. Many antigen detection reagents have a sensitivity of more than 95% or even 100% for the detection of infected people with a Ct value of less than 25. These are the very people we hope to identify in infection control who are highly contagious and have the potential to cause super-spread. Jin Dongyan said.

On the other hand, Jin Dongyan also proposed that the entry threshold for antigen detection reagents is relatively low, and the standard of EU certification is not high. The quality of antigen testing products on the market is uneven.

"We must strengthen quality control and supervision, and users must also purchase and use nationally certified and approved reagents."

Antigen detection is more in the initial screening, if the right choice, the sensitivity and specificity of the antigen detection reagent are very good. Jin Dongyan said.

"Regarding the problem of 'false negative', according to the literature, in the process of in vitro infection, the virus replication reaches a peak after 24 hours, according to which it is speculated that the lower limit of antigen detection can be entered 24-48 hours after the infection of the individual, and the reason for the 'false negative' is more likely to be that the CT value is greater than 30 in the later stage of infection, and the antigen test part is negative, and the nucleic acid test is still positive at this time, but the infectivity has been greatly reduced." Huang Ailong added.

"For initial screening and early testing"

According to the plan, 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.

In the application scenario of antigen detection, Huang Ailong analyzed that it is mainly used in the initial screening and early detection. "Because self-testing is convenient and inexpensive, the application and scenario should be the initial screening and early testing, which can be confirmed and re-examined in combination with nucleic acid detection."

The plan also mentions that primary medical and health institutions with nucleic acid testing capabilities should be given the first choice for nucleic acid testing; those who do not have nucleic acid testing capabilities can conduct antigen testing, and do a good job of medical staff training and patient communication 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.

In addition, Huang Ailong stressed that for control, it is important for the government to lead, individual self-testing, and through information means to ensure accurate results, information matching, and effective connection with existing platforms.

Regarding the price of antigen detection, Huang Ailong analyzed that the factory price of the reasonable range is about 5 yuan for 1 person, 8-10 yuan for 2 people, and the terminal price is not more than 20 yuan / person, which is far lower than the current price of products sold in Hong Kong.

But he also said: "At present, the cost of antigen testing is affected by factors such as production scale and raw material sources, and the current cost increase is relatively large, and the supply of key raw materials is in short supply." ”

Zhongxin Jingwei noted that according to the "Plan", grass-roots medical institutions equipped with nucleic acid detection reagents are included in centralized bidding and procurement, and can continuously reduce the price of testing reagents and reduce the burden of testing reagent costs through centralized procurement at the provincial level.