Singapore studying feasibility of saliva tests

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Some experts say it reduces risk of infection for healthcare staff, while others say viral load in 'pure saliva' is relatively low

The use of saliva to test for Covid-19 is being considered by the health authorities here, as Singapore ramps up its testing capacity.

Responding to queries from The Straits Times, the Ministry of Health (MOH) said it will "continue to review global and local clinical research and evidence on the feasibility of incorporating saliva testing into (its) testing regime". This is part of regular assessments on the suitability of new testing technologies, its spokesman said.

Saliva testing is already being administered in Hong Kong, Japan and the US as it is non-invasive and less uncomfortable than nasal swab tests.

Those who push for the method say it also reduces the risk of exposure and infection for healthcare staff.

Some experts, though, are questioning the reliability of using saliva samples to detect Covid-19.

They note that even as some research may suggest saliva sampling could be comparable to swabbing when conducting polymerase chain reaction tests, the saliva sample should include throat secretions, which generally have a higher viral load, to yield more accurate results.

Associate Professor Hsu Li Yang, programme leader of infectious diseases and co-director of global health at the National University of Singapore's Saw Swee Hock School of Public Health, said the viral load in "pure saliva" is relatively low, whereas "secretions from the back of the throat, which includes the oropharynx and nasopharynx, generally have a higher viral load".

The process of obtaining saliva and throat secretions may also generate respiratory droplets, which could be a concern if the saliva is collected in a crowded place without proper infection control and cleaning measures, Prof Hsu said.

Still, saliva testing is not without its merits.


Depending on the testing strategy and the population targeted for testing, administering saliva tests could reduce bottlenecks at mass testing centres as it would require fewer supervisors, who need not be medically trained for swabbing, said Prof Hsu.

Currently, incoming travellers at Hong Kong airport are required to undergo saliva tests, as these are fast to administer.

Associate Professor Alex Cook, vice-dean of research at the Saw Swee Hock School of Public Health, said saliva testing - if approved here - could be "more palatable to groups who might baulk at being swabbed", for example, young children.

As research continues in this area, Singapore-based molecular diagnostics company Lucence and the Agency for Science, Technology and Research have come up with a saliva collection kit called Safer-Sample.

About 2ml of saliva is collected through a funnel connected to a collection tube. A bottle of stabilisation fluid containing a reagent is then mixed into the sample, which stabilises the viral RNA - the genetic material of the virus - at room temperature for up to one week.

The Straits Times understands the test kit is undergoing clinical validation studies to assess its feasibility.