The Difference Between The Performance Of The 6 Nucleic Acid Reagents Is Calling For Priority Collection Of Lower Respiratory Tract Specimens.

The office of the national health and Health Committee and the office of the State Administration of traditional Chinese medicine (TCM) issued a new diagnostic and therapeutic plan for pneumonia of new coronavirus (trial version fifth), which added "clinical diagnosis" in the case diagnosis classification of Hubei Province, so that patients can receive standardized treatment as soon as possible in accordance with the confirmed cases, and further improve the success rate of treatment.

According to the plan, the recent suspected cases in Hubei were investigated and the results of diagnosis were revised, and new patients were diagnosed according to the new diagnostic classification. In order to be consistent with the case diagnosis classification issued by other provinces in the whole country, the number of clinical diagnosis cases was incorporated into the number of confirmed cases in Hubei since February 13th.

In spite of this, there is still a difference in the performance of the kit as one of the "gold standards". In the industry, the throat swabs used in the kit are not accurate, and the transportation process is difficult to control.

In February 12th, Guo Yuanyuan, the attending physician of the Chongqing Municipal People's Hospital, examined the performance of 6 new domestic coronavirus nucleic acid test reagents in the Chongqing medical journal, and compared the performance of 6 different nucleic acid reagents.

"Reagents do have performance differences. The swallowing of pharynx and nasal swabs is not the main problem. The new crown pneumonia is mainly located in the deep part of the lung. The lower respiratory tract should be collected first. " The deputy director technician of the Zhou Wen Ying, laboratory department of the Third Affiliated Hospital of Zhongshan University, told the twenty-first Century business reporter.

Nucleic acid reagents vary greatly in performance.

In February 12th, Guo Yuanyuan, the attending physician of the Chongqing Municipal People's Hospital, examined the performance of 6 new domestic coronavirus nucleic acid test reagents in the Chongqing medical journal, and compared the performance of 6 different nucleic acid reagents. The 6 test boxes were divided into six groups: group A (Hunan Sheng Xiang Biotechnology Co., Ltd.) and group B ( Cajudi Biotechnology Co., Ltd., group C (Jiangsu Shuo Shi biological Polytron Technologies Inc), group D (Chongqing Zhongyuan Biotechnology Co., Ltd.), group E (Zhongshan University Da'an gene Limited by Share Ltd), F group (Beijing Zhuocheng Hui Sheng bio Polytron Technologies Inc).

The results showed that in the accuracy of the six kits, C reagent and F reagent (Hui Sheng Biology) performed well, and the ORF1ab and N genes of the new coronavirus (2019-nCoV) could be detected. As for the other four kits, D reagent lacks the ability to detect the N gene of the new crown virus, while the A, B and E reagents do not detect the ORF1ab of the new crown virus.

In the overall detection rate, the detection rate of A reagent was 66.6% (4/6), the detection rate of B reagent was 66.6% (4/6), the detection rate of C reagent was 100% (6/6), the detection rate of D reagent was 50% (3/6), the detection rate of E reagent was 83.3% (5/6), and the detection rate of F reagent was 100% (E).

In this paper, it is mentioned that the patients who have been diagnosed as the initial stage of infection will theoretically have higher viral load. The CT value of the corresponding test results should be smaller and smaller. However, in the experiment, only the CT values of the 3 test results of F reagent (N and ORF1ab), E reagent (ORF1ab) and A reagent (ORF1ab) have a trend change.

What causes difference in performance?

Why are these kits different in terms of detection performance? This paper points out two reasons. First, it may be related to reagent primer design. Second, it may be related to the detection sensitivity of each point. The samples used in this experiment are weakly positive, and the sample concentration is relatively low.

However, the paper also pointed out that the sample size of the experiment is limited, and the experimental results do not necessarily reflect the overall detection performance of the reagent.

In this experiment, only one patient (male, 51 years old) received throat swabs at different time intervals. In addition, apart from the detection ability of the kit itself, in actual detection, human error and improper operation may occur in the detection process, so operators should strictly follow the standard operation procedure and strict quality control under the protection of biological safety, so as to avoid false negative and false positive results due to the original operation.

It is worth noting that the samples collected from the experiment were throat swabs. A research article published in the February 12th issue of Chinese Journal of zoonosis pointed out that the content of virus in sputum specimens was higher than that in throat swabs. Sputum samples were better than pharyngeal swabs, and their throat swabs and sputum samples were examined by kits. Two cases of throat swabs were negative, while sputum samples were positive.

The viral content of sputum specimens is higher than that of throat swabs. It may be because the new coronavirus mainly infect the lower respiratory tract cells, and the virus can spread to the upper respiratory tract through cough and other clinical manifestations. Therefore, at the initial stage of infection, viruses tend to focus on the lungs.

This study suggests that the negative detection of swab nucleic acid should be used as a standard to exclude infection and cure. In the process of implementation, caution should be taken, and other specimens such as sputum should be collected when necessary.

In February 4th, Li Xingwang, a member of the national medical expert group and chief expert of the center for infectious diseases diagnosis and treatment of Beijing Ditan Hospital, said at the national health and Health Committee Conference: "from respiratory tract specimens, the sensitivity of alveolar lavage fluid is higher than that of sputum, and the result of sputum is higher than that of the pharynx."

That is to say, from the samples collected from nucleic acid testing, the results of the alveolar lavage fluid are usually the most accurate, while the accuracy of sputum is the second, and the accuracy of the nasopharyngeal examination is the lowest. The diagnosis rate of critically ill patients is high because it can collect bronchoalveolar lavage fluid, but most patients can not collect (bronchoalveolar lavage fluid).

In addition, the diagnosis of new coronavirus has its particularity. Patients with new coronavirus who are infected with the new coronavirus may have clinical symptoms at the early stage, such as fever. If there is no cough, the virus may not be released rapidly in the patients, and the amount of virus in the upper respiratory tract, including nasopharynx is very small, mainly in the lungs. At this point, if the nasopharyngeal test is taken for testing, the results may be negative or may lead to missed detection.

But for this reason, medical staff also told the twenty-first Century economic news reporter: "so the patient's infectivity is also small, because the upper respiratory tract has not been detected, suggesting that it is not infectious. There are also some retrospective studies showing that in some cases, there is a difference in accuracy between patients with severe and mild diseases.

The first challenge is to overcome the lack of capacity, non-standard and suspected cases. This has been alleviated by the fast approval of the FDA. But the second challenge is coming, that is, the consistency of the quality of the kit, and the possibility of missing detection and error detection in testing speed. An in vitro testing industry in Southern China said to reporters on twenty-first Century economic report.

With the inclusion of clinical diagnostic criteria such as CT in Hubei, the diagnosis of new crown pneumonia has been alleviated.

Zhou Wenying told reporters on twenty-first Century economic report: "at present, other provinces and cities are able to do CT and nucleic acid in a timely manner, and all of the confirmed cases are treated and the relative pressure of diagnosis is smaller."

?