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Researchers from Wuhan use oropharyngeal secretions to improve SARS-CoV-2 detection

WUHAN, China: As researchers continue their quest to better understand the SARS-CoV-2 virus, a new study has aimed at improving the detection of SARS-CoV-2 ribonucleic acid. By using oropharyngeal secretions instead of nasopharyngeal swabs (NPSs) for nucleic acid amplification tests (NAATs) for SARS-CoV-2, the researchers managed to reduce the number of false-negative results from testing of patients who had apparently recovered from the disease.

According to the researchers, sampling of oropharyngeal secretions is a simple procedure that can be performed in various settings. It not only minimises the contact between healthcare workers and patients, but also reduces the risk of virus transmission.

The study was led by Dr Jingzhi Ma, associate professor and head of the Department of Stomatology at Tongji Hospital at Tongji Medical College of Huazhong University of Science and Technology in Wuhan. The study included 75 COVID-19 patients who had seemingly recovered and were ready for discharge. The patients had tested negative using two consecutive NAATs of NPS viral samples. However, after having repeated the testing using oropharyngeal secretions, the researchers reported that a few patients were found to be positive.

Since the researchers had detected potential false negatives in the first cohort, they collected 50 additional samples from COVID-19 patients who were recovering from the disease.

The researchers compared the diagnostic values of the two viral ribonucleic acid sampling methods and found that the oropharyngeal secretions obtained from two of the 75 subjects in the first study yielded positive results for SARS-CoV-2 nucleic acid. In the second study, the oropharyngeal secretion samples were found to be significantly more sensitive for the detection of the virus than the NPS samples, and they missed only 14% of positive cases compared with 59% for the NPS samples.

“The NPS test has a risk of sending home more patients who still have the infection, while the oropharyngeal secretions test will make such errors in fewer patients,” Ma noted. He added that, although oropharyngeal secretion sampling improves the accuracy of SARS-CoV-2 nucleic acid testing, this conclusion is based on a small sample size.

The study, titled “Oropharyngeal secretion as alternative for SARS-CoV-2 detection”, was published online on 2 July 2020 in the Journal of Dental Research.

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