COVID-19: Saliva tests could detect silent carriers

Date:
September 28, 2020
Source:
Hokkaido University
Summary:
Testing self-collected saliva samples could offer an easy and
effective mass testing approach for detecting asymptomatic COVID-19.



FULL STORY ========================================================================== Testing self-collected saliva samples could offer an easy and effective
mass testing approach for detecting asymptomatic COVID-19.


========================================================================== Scientists at Hokkaido University and colleagues in Japan have
demonstrated a quick and effective mass testing approach using saliva
samples to detect individuals who have been infected with COVID-19 but
are still not showing symptoms. Their findings were published in the
journal Clinical Infectious Diseases.

"Rapid detection of asymptomatic infected individuals will be critical
for preventing COVID-19 outbreaks within communities and hospitals,"
says Hokkaido University researcher Takanori Teshima, who led the study.

Many of the world's governments are showing reluctance to re-institute
full national lockdowns as second waves of COVID-19 infections loom on
the horizon.

Testing and tracing systems will need to be ramped up in order to detect
and isolate people who have the virus as early as possible.

Teshima and colleagues tested and compared the nasopharyngeal swabs and
saliva samples of almost 2,000 people in Japan who did not have COVID-19 symptoms. Two different virus amplification tests were performed on
most of the samples: the PCR test, which is now well-known and widely
available around the world, and the less commonly used but faster and
more portable RT-LAMP test.

The number of positive and negative results in all samples was very
similar, with the nasopharyngeal swabs and saliva samples able to
detect those with the infection in 77-93% and 83-97% of subjects,
respectively. Both two tests were also able to identify those without
the infection in greater than 99.9% of subjects. The virus loads
detected in nasopharyngeal swab and saliva were equivalent and highly correlated. Teshima says, "PCR sensitivity is much higher than previously thought 70% that came from initial data of symptomatic patients." While finding both nasopharyngeal and saliva samples have high sensitivity
and specificity to the SARS-CoV-2, Teshima says "Saliva testing has
significant logistic advantages over the commonly used nasopharyngeal
swab testing." "Self- collection of saliva is painless for examinees,
and more importantly, it eliminates the close contact with the examiners, reducing the risk of viral exposure." "We also found that it is unlikely
that the sensitivity of RT-LAMP is significantly less than that of the
PCR test, suggesting that it might be a useful alternative for diagnosing COVID-19 infection, especially where diagnosis is required at the point
of sample collection, like in sports venues or at airports," says Teshima.

Researchers point to a limitation of the study that they did not follow
up with clinical outcomes. Nonetheless, they suggest that the results
give good indication that mass screening using self-collected saliva
and rapid RT-LAMP testing could provide easy, non-invasive, quick and relatively accurate results, with minimal risk of viral transmission to healthcare workers.


========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Isao Yokota, Peter Y Shane, Kazufumi Okada, Yoko Unoki, Yichi Yang,
Tasuku Inao, Kentaro Sakamaki, Sumio Iwasaki, Kasumi Hayasaka,
Junichi Sugita, Mutsumi Nishida, Shinichi Fujisawa, Takanori
Teshima. Mass screening of asymptomatic persons for SARS-CoV-2
using saliva. Clinical Infectious Diseases, 2020; DOI:
10.1093/cid/ciaa1388 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200928103424.htm

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