[answer the question of "epidemic disease" Recently, several domestic novel coronavirus nucleic acid testing laboratories were exposed to illegal mixed testing operations. The staff of the institutions involved extracted 1/n sample size from n throat swab collection tubes, and then mixed them together for subsequent testing. This operation will artificially dilute the sample concentration, resulting in reduced detection sensitivity. Wuyan, chief technician of Laboratory Department of Tianjin TEDA hospital Not long ago, panxuhong, deputy director of the Beijing Municipal Public Security Bureau and spokesman, reported at the news conference on epidemic prevention and control in Beijing that Beijing Zhongtong lambo medical laboratory Co., Ltd. had seriously violated the operating specifications for nucleic acid detection of novel coronavirus. Knowing that excessive mixed detection might lead to inaccurate detection results, it still carried out multi tube mixed detection, which was suspected of interfering with the prevention and control of infectious diseases. So, what's the matter with excessive mixed inspection? And why does it lead to inaccurate test results? The reporter of science and technology daily interviewed relevant experts. Single mining is gradually replaced by mixed mining In the early stage of the outbreak of COVID-19, some areas in China adopted the method of single collection or single detection for nucleic acid detection. "Single collection or single test, that is, when collecting samples, put one person's swab separately in a virus collection tube, which usually contains 3ml of virus preservation solution. During the test, the staff will test each collection tube as an independent sample." Wuyan, chief technician of the laboratory department of Tianjin TEDA hospital, was introduced in an interview with the science and technology daily. In order to improve the detection efficiency, the commonly used method is mixed sampling, that is, multiple samples are placed in a collection tube for subsequent detection. Mixed mining is divided into 5-in-1 mixed mining, 10-in-1 mixed mining and 20-in-1 mixed mining. In order to meet the needs of large-scale screening, this collection method has gradually replaced single collection, and has been adopted by more regions in China. On August 17, 2020, the medical treatment group of the joint prevention and control mechanism of the State Council (hereinafter referred to as the treatment group) issued the notice on printing and distributing the technical specifications for the detection of novel coronavirus nucleic acid 10 in 1 hybrid collection; On January 15, 2022, the treatment team issued the notice on printing and distributing the technical specifications for the detection of novel coronavirus nucleic acid 20 in 1 hybrid collection. The above two documents describe in detail the requirements for the use of the mixed sampling tube and the mixed sampling swab. For the 10 in 1 collection tube, it is required to contain 6ml of guanidine salt or other effective virus inactivator preservation solution; For 20 in 1 collection tubes, it is required to contain 11 to 12 ml of preservation solution of guanidine salt or other effective virus inactivators. Mixed test will dilute the sample concentration "At present, the real-time fluorescent RT-PCR method is mainly used to detect the nucleic acid of novel coronavirus." Chenchunqi, a professor of the school of life sciences of Hubei University, introduced that after the sample detection institution obtains the collection tube, it will extract samples from a collection tube and transfer them to the reaction plate. This process is called "cup splitting", and a "Cup" is a detection flux. After that, the staff will put the test reagent into the "Cup" according to the instructions. The method of mixed detection of multiple samples is called mixed detection, which is an illegal operation. The "excessive mixed inspection" method in this problem is to detect the samples collected from multiple tubes in the way of mixed inspection. It allows several collection tubes to "share" one detection flux for subsequent nucleic acid extraction and amplification, and each collection tube shall "share" one detection flux according to the regulations. Wuyan further explained: "Recently, a number of novel coronavirus nucleic acid testing laboratories in China were exposed to illegal mixed testing operations. The staff of the institutions involved extracted 1/n sample size from n throat swab collection tubes, and then mixed them together for subsequent testing. Although this operation can reduce labor intensity and save reagent cost, it will artificially dilute the sample concentration, resulting in reduced detection sensitivity and increased the possibility of false negative test results, seriously affecting The work of epidemic prevention should be carried out. " "Depending on the type of test reagent, the sample size required for later testing is also different." Chenchunqi, for example, if the specification of the test reagent requires that the sample volume be 200 μ L, then the 200 μ l sample of a single collection tube should be added to the reaction plate for subsequent nucleic acid extraction. However, if 10 collection tubes are mixed and there is a positive sample in one collection tube, only 20 μ l of the positive sample is added to the reaction plate, and the content of novel coronavirus is equivalent to 10 times diluted. Especially when the amount of novel coronavirus is very small, it is likely to cause missed detection. Chenchunqi said that unlike the mixed detection, the mixed detection has been scientifically verified. Whether it is the specification and material of the collection tube or the composition and content of the virus preservation solution, it has been accurately designed, which can meet the requirements of large-scale screening and greatly improve the screening efficiency. (outlook new era)