Covid-19: U-turn on saliva testing as fears grow around nasal swab hesitancy
Friday, 24 September 2021
The Ministry of Health is rethinking its approach to saliva testing, after key medical and lab testing bodies make major changes to their position, with one citing a study showing New Zealanders are reluctant to take Covid-19 nasal swab tests.
The New Zealand Microbiology Network has reversed its own call from less than six months ago, and now believes saliva testing is accurate enough to be used as a substitute for nasal swabs.
However, its preferred method is still the nasal swab. Advice from the Microbiology Network is used as the basis of key Ministry of Health decisions.
International Accreditation New Zealand (Ianz) has also changed the certification attached to some saliva testing labs, opening the door for saliva tests to be used as a substitute for nasal swabs at medical clinics, if labs can present enough evidence their test has been properly validated.
**READ MORE:
* Covid-19: Saliva testing at the Level 4 Auckland boundary
* Covid-19: The issues with saliva tests, and why NZ's rollout has been so slow
* Covid-19: Ministry of Health 'now confident' saliva testing could identify cases early
**
NZ First leader Winston Peters has slammed the ministry for not getting saliva testing in place more widely, and faster, despite the Simpson Roche report recommending it last year.
“By March 2021 we should have been totally been on top of it … these sorts of things, costs and delays, and lack of validation as to what they’re using as a system, is just unconscionable at this point in time,” Peters says.
“I’m not trying to be obstructive, I’m trying to find out why on Earth would you have taken that course of action.”
A saliva testing contract for border workers has been mired in behind the scenes controversy.
A spokeswoman for the Ministry of Health says it is reviewing its position on saliva testing on the back of the Microbiology Network’s changed position.
The ministry’s position has changed in recent months from scepticism to now being “confident” saliva testing could identify Covid-19 cases early.
The Microbiology Network also admits there is a real possibility people have not been getting tested for Covid-19 because saliva testing has not been available.
“A recent survey by the Royal College of Pathologists of Australasia reported over two thirds of New Zealanders did not seek testing when they had symptoms consistent with Covid-19,” the Microbiology Network said in a statement on September 16.
”Although not explored in this survey it is possible that [nasal swabbing] is one of the barriers to people presenting for testing. Offering alternative sample types as a diagnostic test option in the community could improve population coverage by increasing the overall number of people tested.”
Yale scientist Anne Wyllie who has been dubbed the “spit queen” for her saliva-testing research, says research backing up saliva testing has been around for many months, and the Government was even given advance copies of some of it.
Wyllie’s colleague, Steph Tan, met with the authors of the Simpson Roche report and provided them with a detailed diagram of the saliva testing process. The report eventually recommended, in September last year, that “all efforts should be made to introduce saliva testing as soon as possible”.
Tan says ministry staff privately express their frustration at the saliva testing delays, and she suspects recent changes in their position are less to do with new evidence and more to do with public pressure.
“I know in the media it’s like ‘Government not doing saliva testing, sceptical, rah rah rah’, but there definitely were people [at the ministry] advocating for it with us. They had the same frustrations as us.
“In terms of higher-ups in Government it didn’t take, it wasn’t enough for them to take action on until urgency became the most dire circumstance, and with public pressure as well.”
‘Spit queen’, spits back
Wyllie, a kiwi ex-pat, has been called on by the United States government to provide advice on saliva testing as a representative of SalivaDirect, the only PCR saliva testing protocol to be represented on a White House call involving leading Covid-19 testers.
Yet Wyllie’s critiques of New Zealand’s approach to saliva testing have attracted the ire of the Government’s chosen saliva testing provider, Asia Pacific Healthcare Group (APHG), and its chief executive Anoop Singh, who criticised her for wading into domestic saliva testing debates earlier this month.
“Sorry who is Anne Wyllie? Who is Anne Wyllie? She’s a research scientist sitting in the US on some university campus. How is she qualified?”
Wyllie replied by quoting Singh in a tweet and replying with a hand-waving emoji, saying her “university campus” is Yale University and her qualifications are that she and her Yale colleagues have “developed an open-access FDA EUA (Food and Drug Administration Emergency Use Authorisation) saliva-based PCR test”.
Singh was incensed by an interview on RNZ’s Morning Report where Wyllie criticised APHG’s test for not being diagnostically validated. His comments provoked a social media backlash with one internet user creating a Wikipedia entry for Wyllie, just so Singh would know who she was.
APHG was awarded a $60 milion saliva testing contract for border workers over a competitor, Rako Science, which has a diagnostically validated test which uses a similar protocol to the one Wyllie developed. Diagnostic validation is seen as a key tool for assessing just how accurate a test is.
In more recent statements APHG has claimed its test is also diagnostically validated, but has refused to provide the data behind it, as Rako Science has done.
Wyllie says the practice in the US is to publish such data publicly once something secures FDA approval, but that is not the case in New Zealand.
‘Disgraceful’
Peters, was listening to same radio interview with Wyllie that Singh heard, but it provoked a different reaction from him.
He wrote a letter to the Auditor-General, asking for an investigation, and questioning how the $60m saliva testing contract for border workers was awarded to APHG in the first place.
His letter asks for answers around what role APHG having been part-owned by NZ Super Fund might have played in it securing the contract.
“I’m confident in what Anne Wyllie says because there’s been serious verification and validation internationally of what she’s saying … and she has no financial interest in what she’s saying at all.”
Wyllie’s SalivaDirect protocol has been provided free of charge to labs, as part of Yale’s public health mission.
Peters also criticised Singh for his attacks on Wyllie’s credibility.
“It’s a disgraceful attempt to discredit a thoroughly creditable [internationally] acknowledged person. That’s what’s wrong about this.
“Whereas on the other side, when you look at who is doing the discrediting, the first question is: so what are your qualifications?”
Opportunity for saliva testing to expand
The changes to Ianz accreditation could result in saliva testing rolled out more widely. Being approved for diagnostic use means doctors will be able to offer it to patients as a Covid-19 test. Saliva testing was previously approved only for “surveillance” testing.
Wyllie says approving tests for “surveillance” first, and “diagnostic” purposes later, is the reverse of how things work overseas.
Less sensitive tests are approved for diagnostic purposes first, because they are more likely to be able to detect Covid-19 in people who have symptoms, or larger viral loads.
With surveillance testing you are trying to find Covid-19 among a population without symptoms, meaning they probably have lower quantities of the virus in their system.
This makes a more sensitive test more crucial for surveillance testing.
Igenz, the lab that Rako Science uses, has received this new form of accreditation allowing its tests to be used for diagnostic purposes, as has Hill Laboratories. Most saliva-testing APHG labs have received this accreditation too.
Rako Science executive directer Leon Grice says it will start providing saliva testing to clinics, as an option, for patients who might present with symptoms.
While Rako Science’s saliva test isn’t being used on frontline border workers, or in public hospitals, private hospitals in the Auckland region are using it.
“[We’re] testing patients the day before, so they can turn up with a negative result, and testing staff twice a day.
“That’s kept us busy, and then we’ve got a massive increase in testing.”
Hill Laboratories chief executive Jonno Hill says its lab, which is accredited for diagnostic saliva testing, uses Wyllie’s SalivaDirect protocol, which has been validated internationally.
To validate domestically it used “spiked” samples of Covid-19. This is something which APHG has done as well. However, APHG has said it also used real-world saliva samples from the Jet Park quarantine hotel.
There are problems with securing samples from Jet Park. One is that it has often been difficult to secure paired samples to test how a saliva test compares to nasal swabbing.
The second is that when people get to Jet Park they are likely to already have large viral loads, making it easier to detect Covid-19 in their system, and therefore difficult to get a true read on how sensitive a test is.
Hill acknowledges there are issues with using spiked samples to validate, but says his laboratory has the added security of using Wyllie’s internationally recognised saliva testing protocol, which has been validated overseas using real-life samples of Covid-19.
“Every lab in the world which wants to setup that SalivaDirect method doesn’t need to redo that full diagnostic validation every time, you just need to make sure you set it up in the way that it should be setup and then do a second-tier validation.”
Singh previously told Stuff the APHG process is different from SalivaDirect and basically treats saliva testing as you would other PCR samples. He says SalivaDirect is an “odd” modification of how PCR tests for other respiratory illnesses are run.
“They’ve actually bypassed a critical step that is the extraction of the RNA material.”
Wyllie says the same methods used for other types of samples do not work well on saliva, and that the insertion of a heat treatment step present in SalivaDirect, in place of RNA extraction, makes saliva testing faster, cheaper, and less resource intensive.
Tan has provided the Government with research indicating saliva testing could be as accurate as nasal swabs, and better at early detection, along with cost comparisons showing that, while nasal swab testing might cost up to $200 per test, saliva testing with the SalivaDirect method costs less than $7 per test. Figures provided under the Official Information Act indicate each nasal swab test costs the taxpayer $138.
Wyllie says the true proof is that their protocol has been validated overseas, and has been used to control outbreaks.
She believes New Zealand and Australian scientists have not been fully across developments in the field because the low levels of Covid-19 in both countries have meant they haven’t had to be.
New South Wales health, for example, has collected saliva using swabs, something Wyllie definitely does not recommend as a collection method.
“This is a constantly evolving area, and every now and then, when I get these papers, when I find these new pieces of evidence, I do flick them through to ESR, [and say] ‘hey, look at this’.”