Wednesday, April 22, 2020

Accuracy of throat gargle used for nucleic acid detection of SARS-CoV-2 higher than that of nasal swabs

Reporter : Cai Mingjie
Source : China News Network.
Ref : http://news.sciencenet.cn/htmlnews/2020/4/438764.shtm
Translation, editing : Gan Yung Chyan
                                  / KUCINTA SETIA

Image courtesy : Teller Report

According to the Guangzhou Institute of Respiratory Health on 22 April 2020, there is progress in the research of nucleic acid detection of the virus SARS-CoV-2 (covi, in short). The progress is first published by  the Chinese journal "Clinical Infectious Disease" in a report by the First Affiliated Hospital of Guangzhou Medical University, the National Clinical Research Center for Respiratory Diseases, and Deputy Director of Guangzhou Respiratory Health Research Institute Li Shiyue. This is a result of the research conducted by Zhong Nanshan team's chief physician Ye Feng. This study is the first to develop a throat rinse sample for the detection of the virus nucleic acid. At the same time, the teams compared with the detection rate of nasal swabs and found that the positive rate of throat rinse is higher than that of nasal swab samples.

Nucleic acid testing is currently the main detection method for covid infections, but studies have shown that different sampling specimens have different sensitivities to the detection of covi nucleic acids. The optimal sampling specimen conditions should be met: 1. Non-invasive, convenient and easy to perform; 2. High positive rate of viral nucleic acid test; 3. No need to come into contact with patients during sampling; 4. Avoid aerosol biological safety issues as much as possible.

Nasopharyngeal swabs are currently the most commonly used samples for the detection of nucleic acid in covi, and studies have shown that the positive rate of detection of nucleic acid in the virus is higher than that of pharyngeal swabs. However, patients with nasal swab sampling generally have obvious discomfort. Secondly, nasal swab sampling cannot avoid the problem of increased risk of infection by the sampler due to contact with the patient. There is a need to develop new, safe, convenient, and operable samples to detect covi nucleic acids.

In response to this problem, Li Shiyue and Ye Feng's team proposed a sampling method for pharyngeal gargle, which can obtain more epithelial cells by shaking the posterior pharyngeal wall with sterile saline to increase the positive rate of detection. To this end, they collected throat swabs and nasal swabs of patients with novel coronavirus pneumonia (covid, in short) at the same time for the detection of covi nucleic acid, and compared the positive rates of the two.

A total of 11 patients diagnosed with covid were included in the study. Among them, 6 patients with positive sputum covi test were still in hospital isolation, and the remaining 5 patients had reached the discharge standard and entered the 14-day observation period. There were 9 males and 2 females, aged 26 to 83 years. A total of 24 pharyngeal lavage and nasal swab specimens were collected, and the average number of days from the onset of detection was (53 ± 2) days. Six cases of nasal swabs were detected negative for the new crown nucleic acid virus, and the corresponding nasal swab new crown nucleic acid virus test was positive. 17 cases of nasal swabs were tested negative for new crown nucleic acid virus, and their corresponding nasal swabs were tested negative for covi nucleic acid.

At present, the pandemic situation is severe. As a non-invasive, easy-to-use and effective sampling method, pharyngeal lavage fluid can be used for nucleic acid detection of covi. The patients are isolated  to avoid contact with infected patients and reduce the risk of infection by medical staff. At the same time, it can reduce the waiting time for sampling, due to the huge number of infected patients, limited medical staff and busy clinical work.

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