COVID testing using pooled samples showed high accuracy, low cost

Date:
October 13, 2021
Source:
American Society for Microbiology
Summary:
Testing pooled saliva samples twice weekly for SARS-CoV-2 on
a residential college campus yielded a greater than 95 percent
agreement with the gold standard for accuracy -- nasopharyngeal
diagnostic samples tested singly.



FULL STORY ========================================================================== Testing pooled saliva samples twice weekly for SARS-CoV-2 on a residential college campus yielded a greater than 95% agreement with the gold standard
for accuracy -- nasopharyngeal diagnostic samples tested singly. At an
average of 665 tests per week, the cost, just $0.43 per sample, likely
remains the least expensive method to date. The research is published
this week in Microbiology Spectrum, a journal of the American Society
for Microbiology.


==========================================================================
"Our study demonstrates a significant step forward for achieving rapid
test results on a large scale, while preserving supplies and reducing
costs," said study author Daniel R. Sharda, Ph.D.

Using pools of ten samples, the test provides results in less than 8
hours, and is among the most sensitive available, detecting virus at
very low viral load, according to the report. This approach enabled
successful screening of 43,884 samples, detecting 83% of the semester's COVID-19 cases.

"Future pandemics should use pooled strategies from the very beginning,
when tests are otherwise limited," said Dr. Sharda, who is associate
professor and chair in the Department of Biological Sciences, Olivet
Nazarene University, Bourbonnais, IL.

In the study, students submitted saliva samples once or twice weekly
during spring semester, 2021. Saliva samples were collected every weekday before 9am and delivered to the testing lab. "We first combined saliva
in pools of 5 and 10 samples on the first RT-qPCR [reverse transcription quantitative PCR] run and then tested positive pools at the individual
level in a second RT-qPCR run," said Dr. Sharda.

"Positive individuals were notified to begin isolation immediately after
being flagged as positive, and close contacts were told to quarantine
shortly thereafter," said Dr. Sharda.

The investigators noted that saliva sampling is noninvasive, does not
require a transport medium and is stable at room temperature for at least
24 hours. Self- collection by students was handled via the honor system,
and fewer than 1% of samples were invalid, with 92% submitted on the
assigned date.

In the study, 36.2% of those tested were asymptomatic, and 48.3 % of participants reported experiencing "very mild" symptoms at the time
of testing.

This suggests that without the mandatory testing, 84.5% of students might
not have gotten tested on their own at the time of screening, according to
the report. Furthermore, only 56% developed flu-like or severe symptoms
during their illness. These results raise the possibility that COVID-19 contagion would have swept the college without the testing program.

The motivation for this research was "a very difficult and unpredictable
fall semester in 2020, when we relied solely on testing self-reporting symptomatic individuals," said Dr. Sharda. The large caseloads
"were challenging to manage, and the college experience was
very restrictive. None of us wanted to live through that again."
"We also recognized that our campus is an integral part of our
local community, so our cases would surely spread off-campus and
possibly reach more vulnerable individuals. We felt an obligation
to our local community to do better," said Dr. Sharda. "Our pooled
saliva approach puts routine COVID-19 testing within reach for
smaller organizations and countries where resources are limited." ========================================================================== Story Source: Materials provided by
American_Society_for_Microbiology. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Nicole A. Vander Schaaf, Anthony J. Fund, Brianna V. Munnich,
Alexi L.

Zastrow, Erin E. Fund, Tanner L. Senti, Abigail F. Lynn, Jonathon J.

Kane, Jennifer L. Love, Gregory J. Long, Nicholas J. Troendle,
Daniel R.

Sharda. Routine, Cost-Effective SARS-CoV-2 Surveillance Testing
Using Pooled Saliva Limits Viral Spread on a Residential College
Campus.

Microbiology Spectrum, 2021; DOI: 10.1128/Spectrum.01089-21 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211013131558.htm

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