On January 12, Tianjin launched the second round of full staff nucleic acid detection.
The Tianjin epidemic is the first large-scale Omicron prevention and control encounter in China. The detection of covid-19 virus is an important part of epidemic resistance. From the experience of public epidemic prevention of Omicron in Britain and America, the use of nucleic acid test (diagnosis) + family self-test (screening) can achieve the effect of 1 + 1 > 2, more effectively block the transmission of Omicron, and is a public health and epidemic prevention means to effectively control the epidemic situation.
On January 9, Andon Health Co.Ltd(002432) submitted the proposal on using family self-test box to realize Omicron covid-19 epidemic prevention 1 + 1 to Tianjin epidemic prevention and control headquarters.
covid-19 family self-test has been the main means in European and American countries
Because of the havoc of Omicron, the number of positive patients in Europe and the United States is rising sharply. Covid-19 detection is always an important part of anti epidemic. However, according to the newly published chapter of the British body anti-virus experiment, some patients already have infectious energy before PCR nucleic acid test can detect positive, which is transmitted first and then the disease occurs.
For Omicron, nucleic acid collection test (diagnosis) + family test (screening) can achieve the effect of 1 + 1 > 2, and can more effectively block the transmission of Omicron. It is a public health and epidemic prevention section to effectively control the epidemic situation.
Professor Zhang Yan from the school of pharmacy of Tianjin University said that at present, the real-time fluorescent quantitative PCR nucleic acid detection applied in screening and the constant temperature detection relying on DNA amplification need professional personnel and professional instruments and equipment, including many covid-19 antigen detection methods based on specific antibodies, and fluorescent markers also need to be used to ensure the accuracy of detection. These methods need professional equipment and personnel to operate. In the face of large-scale nucleic acid screening, they are time-consuming, labor-consuming and high economic and social costs. Universal testing will also increase the risk of exposure to infectious environments.
According to Zhang Yan, at present, the family covid-19 self-test reagent uses antigen reagent rather than nucleic acid reagent. Antigen detection is aimed at virus N protein, and virus mutation mainly occurs in S protein. Therefore, no matter how the virus mutates, the test results will not be affected.
"Antigen reagent combines the characteristics of high early diagnosis accuracy of nucleic acid reagent and rapid detection of antibody reagent. It can be detected on the first day of infection with covid-19 virus. It is easy to operate and does not need special equipment or instruments." Zhang Yan said that the results from sampling to analysis are generally within 20 minutes, and the accuracy is close to that of nucleic acid reagent.
As early as November 2020, the UK carried out the first universal covid-19 virus "general test" in Liverpool by means of antigen reagent. At the same time, more reliable nucleic acid test will be used for suspected cases.
After the United States, Britain and other countries take antigen reagent as the main means of covid-19 screening, the screening efficiency has been significantly improved. Therefore, many overseas countries are adopting the method of family covid-19 self-test.
reusable covid-19 home self-test chip
At present, the family covid-19 self-test reagent mainly adopts the traditional colloidal gold test strip method which uses the naked eye to distinguish the color. Although this method is relatively mature and has high accuracy, it also has its limitations. The loading amount is limited and it is unable to amplify the virus antigen, resulting in low detection sensitivity.
Scientists all over the world are looking for more efficient, low-cost and safer means of covid-19 family self-test.
Recently, Professor Zhang Yan, in cooperation with Harvard University and other scientific research institutions in the United States, invented a home covid-19 self-test system that does not require any electronic and optical device equipment and operation skill training. The system can detect the results within 5 minutes at the fastest, and provide visible results with intuitive color comparison. The single microfluidic chip can be used more than 50 times, which greatly reduces the detection cost and is very suitable for ordinary families and individuals. The achievement was published in the international journal small on December 29, and was selected as the inner cover of the current period by small.
According to reports, the research team creatively used microfluidic chips instead of capillary chromatography test strips, and the sample loading was dozens of times higher than that of traditional test strips. At the same time, it avoids the risk that the conventional method using colloidal gold is easy to miss the detection of low virus load samples.
"The detection chip uses two kinds of micro spheres and nano spheres modified by different antibodies. The colors are white and red respectively." Zhang Yan introduced that when there is no virus antigen in the sample, the red nanospheres can be quickly filtered by the fence with specific interception aperture, so that the detection window presents the white of micron spheres. When covid-19 virus exists, the micron spheres and nanospheres form a complex mediated by virus antigen through surface antibodies, and the red nanospheres cover the white micron spheres, Thus, the detection window displays red visible to the naked eye.
Because the chip is designed with countercurrent function, after the detection, the microspheres can return from the original path and empty the detection window under the washing of normal saline or clean water, so that they can be used for dozens or even hundreds of times.
can China realize covid-19 family self-test
At present, there are many listed companies involved in household covid-19 testing business in China, including Andon Health Co.Ltd(002432) , Zhejiang Orient Gene Biotech Co.Ltd(688298) , Beijing Hotgen Biotech Co.Ltd(688068) , Wanfu biology, Hangzhou Alltest Biotech Co.Ltd(688606) , Hangzhou Biotest Biotech Co.Ltd(688767) , Anxi biology, Shenzhen Yhlo Biotech Co.Ltd(688575) , Wuhan Easy Diagnosis Biomedicine Co.Ltd(002932) , Jiangsu Bioperfectus Technologies Co.Ltd(688399) .
For the implementation of covid-19 family self-test, the most concerned problem is its accuracy. From the current feedback results, many covid-19 family self-test products show very excellent performance.
Zhang Yan said that in the double-blind clinical test of more than 100 users, the detection accuracy of common covid-19 virus and delta variant virus strain was as high as 95.4% and 100% respectively.
The research of Zhang Yan's team also verified the practicability of individual users. It was found that the detection system showed excellent robustness and accuracy under different operation methods (manual sampling speed), operation conditions (temperature, lighting) and operation time (5-120 minutes).
However, according to China's customs data, China's covid-19 antigen reagent was mainly sold to Germany, the United Kingdom, the United States, Canada and Greece in November 2021. So far, no covid-19 antigen reagent has been registered in China.
Insiders said that due to the small number and scattered of new cases in China, it is difficult for reagent manufacturers to collect enough clinical trial cases in accordance with the current regulations of the State Food and drug administration. However, according to the EUA registration requirements of FDA, the certified Andon Health Co.Ltd(002432) , Zhejiang Orient Gene Biotech Co.Ltd(688298) and Aikang technology have completed the clinical trial of covid-19 antigen reagent in the United States.
Zhang Yan said that at present, China still faces a difficult problem in promoting covid-19 family self-test, that is, supervision. How to report the test results, how to avoid concealment, how to audit and verify the authenticity and effectiveness of the test results in the background, and how to make big data statistics are all problems that need to be solved before covid-19 family self-test promotion. However, with the normalization of covid-19 virus prevention and control, covid-19 family self-test is very necessary to be popularized.
