Arushi Bidhuri
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Written By: Arushi Bidhuri | Updated : June 14, 2021 1:06 PM IST
Saliva Tests For Covid-19 More Effective Than Nose-Throat Swab Tests
With extended delays and shortages, testing for SARS-CoV-2 the virus that causes Covid-19 has been a key stumbling point in the fight against the pandemic. Several tests have been developed to detect the coronavirus, using a variety of assays. While some are treated as superior to others, and a few delivers accurate results. The most common methods of testing are the 'stick in the nose' and throat swab tests, but researchers have found that saliva testing might be more effective.
While previous studies had found that nose-throat swab tests are more accurate in detecting positive coronavirus infection, a new report suggests that saliva-based testing can be more accurate at identifying negative cases for Covid-19, with a far less invasive and discomforting process. Researchers from Augusta University in the US have found that saliva testing could be more effective for Covid testing.
As per the team, the inclusion of a simple processing step to saliva samples before testing should enhance coronavirus detection rates, alleviate nasopharyngeal testing problems, and make mass monitoring easier. They discovered that using a bead mill homogeniser to treat saliva samples before real-time PCR (RT-PCR) testing leads to better sensitivity than using nasopharyngeal swab (NPS) samples.
The lead investigator of the study published in the Journal of Molecular Diagnostics, Ravindra Kolhe, said, "Saliva as a sample type for Covid-19 testing was a game-changer in our fight against the pandemic. It helped us with increased compliance from the population for testing along with decreased exposure risk to the healthcare workers during the collection process."
For the study, the team analysed 240 matched NPS and saliva sample pairs for SARS-CoV-2 RNA by RT-PCR in the first phase (protocol U) in the first phase. 189 matched pairs, including 85 that had previously been evaluated using protocol U, were processed in an Omni bead mill homogeniser before RT-PCR testing in the second phase of the study.
A further experiment was carried out with samples from procedure U and SalivaAll to see if bead homogenisation affected clinical sensitivity in NPS samples. Finally, the effectiveness of a five-sample pooling technique was assessed. The Omni bead homogeniser was used to handle twenty positive pools, including one positive and four negative samples before pooling for SARS-CoV-2 RT-PCR testing and comparing to controls.
In the first phase, 28.3 per cent of NPS, saliva, or both samples were positive for SARS-CoV-2. When compared to NPS, the detection rate in saliva was lower (50.0 per cent vs. 89.7 per cent). In Phase II, 50.2 per cent of saliva, NPS, or both samples were positive for SARS-CoV-2. When compared to NPS samples, the detection rate in saliva was greater (97.8 per cent vs. 78.9 per cent). The detection rate for the 85 saliva samples tested with both procedures was 100% for samples tested with SalivaAll and 36.7 per cent for those tested with procedure U.
(with inputs from IANS)
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