Saliva PCR test almost as accurate as nasal/throat swab

An Irish study has shown that a PCR test using saliva to test for Covid-19 is almost as accurate as the current method of swabbing the nose and throat.

According to researchers from the RCSI University of Medicine and Health Sciences, saliva screening is much less invasive than the current method and could enable greater capacity and increased uptake among those who require regular screening.

The study looked at the performance of the established PCR test, which involves nasal and throat swabbing, and the more recently developed SalivaDirect approach, which tests for the virus in saliva specimens.

SalivaDirect was developed by the Yale School of Public Health and has been authorised for emergency use by the US Food and Drug Administration (FDA).

As part of the study, nasal/throat swabs and saliva samples were collected from over 300 symptomatic and asymptomatic participants between November 2020 and March 2021.

The participants included asymptomatic RCSI students and patients admitted to Beaumont Hospital with Covid-related respiratory symptoms.

The study found that 94% of the positive nose/throat samples also tested positive with the saliva samples. Furthermore, 96% of the negative nose/throat samples also tested negative with the saliva samples.

The results are consistent with the original results relating to the SalivaDirect method and indicate that the use of saliva to detect Covid-19 represents an accurate and less invasive alternative to nasal/throat swabbing.

According to the study’s joint lead author, Prof Steve Kerrigan, who is deputy head of the RCSI’s School of Pharmacy and Biomolecular Sciences, this study has “further validated that saliva testing can offer an accurate alternative to the more invasive commonly used nose and throat swabbing method”.

“The saliva sample to test for Covid-19 can be easily collected by the person themselves, so has the potential to increase compliance with screening, particularly those who require frequent repeated testing. As the saliva test does not require a healthcare professional to conduct it, this method also reduces the risk of infection for test centre staff associated with conducting nasal/throat swabbing,” Prof Kerrigan said.

This study was conducted in collaboration with UCD and Beaumont Hospital. Details are published in HRB Open Research and can be viewed here.