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False negatives — when a person carrying a pathogen tests negative — have been reported several times during the Covid-19 pandemic. These results have come up during nasal swab testing of patients who have seemingly recovered from the disease — but have later been found to be still carrying the virus.
Now, researchers have reported that testing of oropharyngeal secretions — secretions from the part of the throat at the back of the mouth — may reduce the number of false negative results. They have published their findings in the Journal of Dental Research.
Oropharyngeal secretions obtained from 2 of the 75 subjects in the first study yielded positive results for SARS-CoV-2. In the second study, oropharyngeal samples missed only 14% of positive cases, compared with 59% for the nasal samples.
Sampling of oropharyngeal secretions is a simple procedure that can be performed in any quarantine setting. It minimises contact between healthcare workers and patients, thereby reducing the risk of virus transmission, the researchers said.
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“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. Although OS sampling improves the accuracy of SARS-CoV-2 nucleic acid testing, it must be emphasised that this conclusion is based on a very small sample size,” Ma said in a statement.
Source: International Association for Dental Research
