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A saliva-based COVID-19
antigen rapid test (ART)
technology co-developed by
the SingHealth Duke-NUS
Academic Medical Centre
and the National University
of Singapore (NUS) will offer a more
pleasant alternative to nasal swabs.
Officially known as PASPORT (Parallel
Amplified Saliva rapid POint-of-caRe Test),
this easy-to-use and painless test is highly
accurate. Compared to the gold standard
Polymerase Chain Reaction (PCR) test,
PASPORT’s sensitivity in detecting the
SARS-CoV-2 virus is 97 per cent, and its
specificity (to detect a true negative result) is
90.6 per cent. These results are comparable
to ART nasal swabs available in Singapore.
While PASPORT is not the first test
that can be used for saliva testing, it vastly
outperforms the handful of existing options,
which have not been accurate enough to be
rolled out at large scale.
One of the major limitations of existing
saliva tests is that they are accurate only after
prolonged fasting, such as in the morning after
waking up. “Should participants eat, drink or
brush their teeth, the concentration of viral
particles in the saliva drops too drastically for
an accurate result. A comparison against two
other existing test kits showed that sensitivity
dropped to approximately 60 per cent and
20 per cent respectively after food,” said
Dr Danny Tng (pictured), Medical Officer, Department
of Infectious Diseases, Singapore General
Hospital (SGH). He is also an adjunct
Research Fellow at Duke-NUS’s Emerging
Infectious Diseases (EID) Programme and
one of the key inventors of PASPORT.
The other inventors include Associate
Professor Melvin Chua from National Cancer
Centre Singapore (NCCS) and Duke-NUS
Medical School, Professor Jenny Low
from SGH and Duke-NUS Medical School,
Professor Ooi Eng Eong from Duke-NUS
Medical School, Professor Soo Khee Chee
from NCCS and Duke-NUS Medical School,
and Professor Zhang Yong from NUS.
PASPORT can be used at any time of the
day, even after meals. Like other ARTs, it uses
nanoparticles to bind the virus. In addition, it
adds a second type of nanoparticle that binds the
first set of nanoparticles to amplify the signal,
allowing it to be
than other lateral
flow tests. Using its
unique viral capture system
with ACE2 proteins, it is also able
to pick up COVID-19 variants, including Delta.
This new kit looks similar to a regular
ART kit. The main difference is that instead
of a nasal swab, users will collect a small
amount of saliva in a funnel, drop some
saliva in the first channel of the test kit, and
wait for up to 15 minutes for results. If results
are negative, they will drop more saliva into
the second channel of the test kit and wait
for another 15 minutes for amplified results.
Therefore, this self-administered test can be
completed in as soon as 15 to 30 minutes.
Dr Tng noted that globally, there is a high
demand for ART over PCR testing. This is
because the latter requires specially trained
personnel for sample collection, processing and
interpretation of results, is costlier ($150 per test
on average), and takes up to a day to get results.
“With new COVID-19 anti-viral oral
medications like Molnupiravir, it is very
important to administer these drugs within
the first few days of illness to achieve the
best outcomes. As PCR takes a longer
time, you could miss a critical window for
treatment,” he explained.
Furthermore, saliva antigen tests reduce
the margin of error that occurs when the nasal
swab is not done properly — for instance,
when it is not be inserted deep enough into
the nasal cavity. “Some studies have shown
a 10 per cent difference in accuracy when a
professional does the nasal swab compared to
when users do it on their own,” Dr Tng said.
The saliva test may also be easier to
administer on children who may find nasal
swabs uncomfortable. This convenient
testing method is also important since there
is currently no vaccination available for very
“A test like PASPORT that can be selfadministered
or used on-site at the primary
care setting may mitigate the need for cases
to be managed at the hospitals,” said Prof Ooi.
Manufactured by Singapore-based
company Digital Life Line Pte Ltd,
PASPORT is expected to be available for
consumer use by the end of 2022.
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