Oropharyngeal secretion (OS) testing may reduce the number of false negative results from patients who seemingly have recovered from COVID-19 based on nasal swab testing, according to researchers in the Department of Stomatology at Tongji Hospital of Tongji Medical College of Huazhong University of Science and Technology in Wuhan, China.
The study included 75 COVID-19 patients who were ready for discharge after testing negative using two consecutive nucleic acid amplification tests (NAATs) of viral samples retrieved with nasopharyngeal swabs (NPSs).
After potential false negatives were detected in that cohort, the NAAT results of paired OS and NPS samples collected from 50 additional COVID-19 subjects during their recovery stage were used in a second prospective study to compare the diagnostic values of the two viral RNA sampling methods.
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, OS samples were significantly more sensitive for detecting the virus that NPS samples and missed only 14% of positive cases compared with 59% for the NPS samples.
OS sampling is a simple procedure that can be performed in any quarantine setting and minimizes contact between healthcare workers and patients, the researchers said, thereby reducing the risk of virus transmission.
“The NPS test has a risk of sending home more patients who still have the infection, while the OS test will make such errors in fewer patients,” said study leader Jingzhi Ma. “Although OS sampling improves the accuracy of SARS-CoV-2 nucleic acid testing, it must be emphasized that this conclusion is based on a very small sample size,” said Ma.
The study, “Oropharyngeal Secretion as Alternative for SARS-CoV-2 Detection,” was published by the Journal of Dental Research.