Covid-19: Ministry of Health 'now confident' saliva testing could identify cases early

Tuesday, 31 August 2021

New evidence received in April confirms saliva testing is accurate enough to replace nasal swabs, and could be better for preventing Covid-19 outbreaks, the ​Ministry of Health says.

The ministry has also admitted shortcomings with the validation of its chosen test are the reason it does not want to use it during a community outbreak.

Stuff earlier reported on a stoush between ​Rako Science and the ministry over a $60 milion saliva testing contract, after ministry boffins passed over Rako’s diagnostically validated test in favour of one from the ​Asia Pacific Healthcare Group, a test which was not validated diagnostically but instead validated using artificially “spiked” saliva samples.

“We are now confident that there are situations where saliva testing for Covid-19 may be carried out instead of nasal testing, as a surveillance tool, such as where frequent testing of border workers has the potential to identify cases earlier and before chains of transmission are generated,” a ministry spokeswoman said.

**READ MORE:

* Slow saliva testing roll-out hurting New Zealand's ability to get on top of outbreak: Scientist

* The saliva testing stoush between Rako Science and the Ministry of Health

* Covid-19: New non-invasive saliva tests for athletes before Olympics

* Covid-19: How our testing capacity stood up to the Delta variant

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Since New Zealand went into level 4 lockdown, calls for saliva testing have reached fever-pitch on the back of revelations people connected to the outbreak were waiting days for test results, and queueing for up to 10 hours for a Covid-19 test.

The spokeswoman said in a statement, nasal swabbing had been diagnostically validated, which was why it was needed for use in the general population during an outbreak.

However, the ministry also acknowledged one form of saliva test had already been diagnostically validated, just not the saliva test it contracted for.

“Diagnostic testing, rather than surveillance testing, is needed to confirm a positive Covid-19 test, and to enable genome sequencing of the positive case to be undertaken, which is a vital part of our response.”

The spokeswoman said the ministry had re-assessed its position on saliva testing several months ago in the light of new data.

“Previous evidence had shown that saliva testing was not as sensitive as nasal swabbing, meaning there was the potential for missed infections. A single missed infection could potentially lead to widespread community outbreaks.

“Our position on saliva testing changed in April as a result of new evidence and information and the advice of the ministry’s saliva testing clinical governance group,” she said.

The official roll-out of saliva testing to border workers started on August 11, but the Simpson Roche report called for it last year, shortly after the United States ​Food and Drug Administration (FDA) granted some saliva testing protocols an emergency use authorisation.

Politicians, scientists, and businesspeople have called for polymerase chain reaction(PCR) saliva testing to become more readily accessible to the general population.

Most recently, ​Te Whānau o Waipareira Trust announced plans to test people using Rako Science’s diagnostically validated saliva PCR test, and called for Ministry of Health testing funds to be made available to pay for saliva testing.

​Te Whānau o Waipareira Trust chief executive John Tamihere has rubbished previous ministry claims where it had implied Rako’s saliva test should only be used for “surveillance” testing of border workers, and not the public.

“If it’s good enough to be used for surveillance, what does surveillance mean? Surveillance means we’re under surveillance to look to see if we have a positive.

“Why is it approved for surveillance if you’re not going to use the results? Do they think we’re all thick?” Tamihere said.

Saliva testing holds a number of advantages over nasal swabbing. People are more willing to get tested because it is less unpleasant than a nasal swab test, it requires fewer trained medical staff, is likely to be better at early detection of Covid-19 and, because the test is less invasive, it can also be run more frequently.

Calls for saliva PCR testing have only grown since groundbreaking research into the subject was published in April last year. They further intensified after certain types of saliva testing were given US FDA emergency use authorisation and used to curb outbreaks overseas.

Saliva PCR testing is different from antigen rapid saliva testing. Antigen can deliver results in one or two hours, but carries with it a high error rate. No form of antigen saliva test has received FDA emergency use authorisation.

However, certain forms of saliva PCR testing have, and are still faster than nasal swab testing. Rako Science’s test normally delivers results within 8 hours.

Mobile PCR machines from ​Ubiquitome allow the processing of saliva samples even more quickly, within two hours.

​Ubiquitome chief executive ​Paul Pickering said this sort of testing could take pressure off a centralised lab system during an outbreak, and allow for more frequent testing during more normal times.

“[With saliva testing] there’s much greater willingness of the general population to undertake repeat testing which, frankly, we’re all going to have to get used to in the coming days, weeks and months with Delta.”

Wider acceptance of PCR saliva testing could bring these kinds of resources to the Covid-19 testing fight.

Anne Wyllie, a leading researcher on saliva testing at Yale Universtiy in the US, said saliva testing could be especially helpful within the current outbreak because such tests could better detect Covid-19 among people without symptoms, before they became infectious.

Saliva testing could also draw on lab resources not being used for testing, including from Rako Science which has been outspoken about the need for the country to roll out saliva testing.

Rako Science executive director ​Leon Grice said Rako’s own lab resources were not used for nasal swab testing, so any capacity it provided with saliva tests would be extra to what the Ministry of Health was drawing on within this outbreak, or future ones.

Grice said Rako could ramp up their own capacity to 10,000 saliva tests per day.

​Igenz lab director ​Amanda Dixon-McIver, who has been involved in lab testing of Covid-19 nasal swabs in the past, and whose lab now does Rako’s testing, said extracting saliva samples was itself faster than picking apart a nasal swab. Other parts of the lab processing involved with Rako’s saliva test were automated, further reducing the resources needed.

​Pickering said ​Ubiquitome’s Liberty16 machines, manufactured in New Zealand, and being used for Covid-19 testing around the world, received FDA emergency use authorisation for Covid-19 testing in June and were designed to take pressure off a centralised lab processing system.

“As we’ve seen the problem with Delta is once these infections get start, it’s really hard to stop them. You’ve got to get in early.”