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Saliva Effective as Nasal Swabs in COVID-19 Testing -Study

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In positive patients, they found more copies of the virus in the saliva samples than they had established in the alternative nasopharyngeal deriving a 95 per cent confidence level in the test. When they subjected the patients on admission in hospital after five days on treatment, 81 per cent tested by saliva were positive whereas the nasal swabs were at 71 per cent.
An illustration of how far the swab goes to pick a nasopharyngeal specimen
Saliva samples have similar sensitivity in the detection of SARS – COV- 2, the virus that causes coronavirus disease-COVID-19 just like the currently widely used nasal swabs, a new study suggests. 

The study, conducted by professors at Yale School of Public Health involved 70 COVID-19 positive patients and 495 asymptomatic health workers. The researchers made participants who had been tested through PCR using swabs to collect their saliva which was subjected to a test at the same time.

In positive patients, they found more copies of the virus in the saliva samples than they had established in the alternative nasopharyngeal deriving a 95 per cent confidence level in the test.  When they subjected the patients on admission in hospital after five days on treatment, 81 per cent tested by saliva were positive whereas the nasal swabs were at 71 per cent.

In the arm of the study that involved testing health workers who had no symptoms of the disease, 13 out of 495 tested positive through saliva screening.  Nine of the 13 samples were again tested using nasal swabs and seven of them still tested negative. However, the 13 samples were again taken to another laboratory where they all came out positive.

In the note to the editors, one of the researchers, Prof. Anne Wyllie a pneumococcologist said considering the growing need for tests across the world, their findings provide support for the potential of saliva specimens noting that the method has several advantages as a collection of the saliva by patients themselves negates the need for direct interaction between the patient and the health worker.

Also, she notes that with saliva, the demand for supplies such as swabs and Personal Protective Equipment (PPE) which are in short supply in many countries will be alleviated.

Commenting on the study, Dr Bruce Kirenga, a researcher based at Makerere University Lung Institute said the findings are not just a good development in diagnostics but also strengthen the resolve to cover the mouth where the saliva comes from, making a case as to why using a face mask is key in the fight against COVID-19.

However, the researchers note that this study was small calling for bigger studies such that more evaluation can be done on how the dreaded swabs compare with saliva in terms of sensitivity.     

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