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

Monday, 23 August 2021

Prime Minister Jacinda Ardern extends level 4 lockdown in New Zealand.

A Yale University public health expert urged the Government to address major problems with its saliva testing roll-out just days before the current outbreak. Now she believes such testing could help the country get on top of Delta.

New Zealand’s nasal swab-dominated testing regime has come under huge strain over the past few days. Epidemiologist Michael Baker said the testing system has been pushed “beyond its limits”. Thousands of people have lined up for tests, causing ten-hour long queues and shortages of nasal swabs.

The nasal swab testing system is expensive, as well. Figures released under the Official Information Act reveal it costs $75 to collect each swab and $63 for each test result, a total cost of $138 per test, or nearly $23m for the more than 166,000 tests conducted last week.

Saliva tests, which have helped bring outbreaks under control overseas, have cost US$19 per test, including lab processing.

* Covid-19: Only 386 saliva tests carried out on quarantine staff since January

* Covid-19: Saliva tests may have a place at the border, but not in the community

* Covid-19: Auckland Airport trialling coronavirus saliva test developed by NZ team

Yale school of public health research scientist Anne Wyllie, who has led groundbreaking research into saliva testing, said a proper saliva testing regime could have helped with these capacity issues, while reducing the chance of healthcare workers being accidentally exposed to Covid-19 when administering the test.

Covid-19 measures like vaccine certificates and testing will become the “new norm” for travel, Otte says.

“Often, a person shouldn't just be tested once - they likely need to be tested again to be sure their developing infection wasn't missed the first time.”

“[People] could take a saliva tube home with them, self-collect a few days later and simply drop it off in a box for testing, negating the need for additional attention from a healthcare worker – and importantly, protecting those healthcare workers from potential additional exposure.”

Days before the Delta outbreak, Wyllie, a New Zealand citizen, wrote to Prime Minister Jacinda Ardern and the Ministry of Health urging them to appoint an international panel to sort out issues with the country’s saliva testing regime.

Experts outside Australia and New Zealand should be used because they had more experience with the complicated science of using saliva testing to prevent outbreaks, she said.

“I kindly urge that you appoint a panel of expert and truly external advisers with the required knowledge of molecular biology, medical laboratory science and international standards to review the decisions that have been taken on saliva testing before it’s too late,' she wrote on August 12.

Anne Wyllie, centre, says if the tests weren’t accurate they wouldn’t be able to help suppress outbreaks.

Different saliva test have differing levels of accuracy, and a lot of it comes down to the way in which saliva samples are collected.

The Government has expressed concerns about saliva testing in the past, but Wyllie said it was sensitive enough to use, provided the right test and sampling method was chosen.

“It's frustrating that this [accuracy] is still a question and shows how much misinformation has been passed onto the NZ public.'

Wyllie cited examples like Ohio State University, where up to 8000 saliva tests a day were run allowing students to attend class without any major outbreaks.

“If these [testing programmes] were not sufficiently accurate, they would not be able to stop outbreaks.

There are different methods of saliva collection with very different results for each type.

“These saliva-based testing programmes have used saliva to detect infections before symptoms occur and before the outbreak can spread further.”

Saliva testing holds a number of advantages over nasal swabbing: it is thought to be better at early detection of Covid-19, it cuts down the number of trained medical staff needed for testing, and because the test isn’t as invasive it can be run more frequently.

The Ministry of Health has struggled to stand up a saliva testing regime within the original timeframe.

A $60m contract for saliva-based surveillance testing was put out in February for a mid-April roll-out, but the roll-out actually started on August 11.

Rako Science unsuccessfully bid for the original contract with a diagnostically validated saliva test, already in use among international travellers.

They were passed over in favour of the more established Asia Pacific Healthcare Group, whose test had not been diagnostically validated.

In total, saliva samples from 162 border workers have been collected since the scheme started in August, and 562 border workers have opted-in for saliva testing.

The Ministry of Health said saliva collection sites are now available at 43 collection points across 19 sites, which are mainly managed isolation facilities and ports.

Wyllie’s concern was the Ministry of Health had chosen a testing provider whose tests had not been diagnostically validated using “real world” samples from people who had been infected, which meant its sensitivity to detecting Covid-19 could not be truly known.

The ministry's chosen test was validated by “spiking” saliva with Covid-19 and then checking if Covid-19 could be detected it in those artificially spiked samples.

“If you think about the virus, it is inside your cells, it is trapped in your mucus, it is so integrated with your saliva sample that it requires more robust processing to get your cells open, to access the virus and separate it out,” Wyllie said.

“Spiking doesn't accurately represent the real world situation.”