Saliva swabs "can be as good as, or even better than a nasal swab" when testing for Covid-19, the lead researcher behind a pioneering study into saliva testing says.
It comes amid an increasing call for more saliva tests to accompany nasal tests in New Zealand.
Auckland moved to Alert Level 2 at 11.59pm yesterday, while the rest of the country returned to Level 1, with the decision informed in part by widespread testing in the community.
The recent testing numbers are second only to last August, with over 17,000 test results delivered on Tuesday alone following the discovery of three Covid-19 cases in the community on Sunday. A further three cases were discovered yesterday.
Yale University epidemiology researcher Anne Wyllie told Breakfast today that concerns around accuracy are dependent on "how you're testing that saliva".
"I think that's the problem which has lead to all of this confusion about just how accurate it is," she said.
"You need to figure out which method works best for it and there's been a lot of people who've used, maybe, less good methods on it. And this is why we've got some of this really unclear data about how good it really is."
Wyllie, the lead into pioneering reserch behind saliva testing, said there are promising studies indicating that saliva swabs "can be as good as, or even better than, a nasal swab".
In a submission to the New England Journal of Medicine, Wyllie and her team found that of 70 inpatients with Covid-19, "in some cases, saliva was better for the detection of SARS-CoV-2 and actually, nasal swabs do have, also, a high risk of negatives as well".
She also questioned people who claimed not to feel any discomfort while undergoing a nasal swab, saying, "How well was that nasal swab taken and could that swab also be leading to a false negative because it wasn't taken properly?"
Wyllie said that, while there was hesitancy around saliva testing's accuracy in asymptomatic people last April and May, "we've come a long way since then".
Michael Baker said the country’s alert levels and its testing of border workers needs “fine-tuning”.
"In the end, viral load is viral load. It isn't about whether a person is symptomatic or asymptomatic. It's how much virus do they have in there and how sensitive is your test to be able to detect low levels of that virus before someone becomes symptomatic and transmits the virus to others?"
She said she believes New Zealand is slow to embrace saliva swabbing on a larger scale because "it's got a lot at stake".
"It has done an incredible job to get cases down to near non-existent and it's a huge responsibility about having something in place that's going to continue to protect the border as well as what's been done so far. But then something like this could actually help to protect it further."
Wyllie said while she was proud of New Zealand for "buying itself time to figure these things out, a lot of time has since passed and I would have expected a lot more of this to have been figured out a lot sooner when the rest of the world is already rolling tests and strategies like this out".
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