COVID-19: Expert warns business coalition calling for rapid antigen tests to proceed with caution due to unreliability

A coalition of 25 major New Zealand businesses is seeking urgent approval from the Government to import rapid antigen tests into the country to protect critical worksites - but one expert is urging the coalition to proceed with caution.

On Wednesday, it was announced that 25 of New Zealand's largest businesses had formed a coalition to jointly import 370,000 rapid antigen tests for COVID-19 into the country. The coalition is calling on the Government to issue emergency approval for the delivery, which would allow the tests to be distributed to worksites across a range of sectors - including manufacturing, energy, food production, telecommunications, freight, aviation and aged-care.

Rapid antigen tests are fast-acting diagnostic tests commonly used overseas for the detection of SARS-CoV-2, the virus that causes COVID-19. The tests directly detect the presence or absence of an antigen, providing a positive or negative result in around 15 minutes. Comparatively, PCR tests - which detect genetic material from a specific organism, such as a virus - often take between 24 and 72 hours to process. New Zealand has relied predominantly on PCR testing throughout the pandemic, in accordance with its elimination strategy.

"What we are seeking is urgent approval from the Government to allow for the importation of rapid surveillance tests as a critical part of health and safety management in the workplace," Don Braid, Mainfreight's managing director, said on Wednesday.

"This is business wanting to take care of their people from a health and safety perspective and to keep their sites operational. Vaccinations and testing are key to this and it is bewildering that the rapid testing we are using in 26 locations around the world is unavailable to us at our home base in New Zealand.

"We believe the Government shares our concern that the addition of antigen testing cannot suffer the long delays that occurred in introducing saliva testing. With the current Delta outbreak we are confident they will act decisively and work with us to make it happen."

But University of Otago clinical microbiologist James Ussher is warning the coalition to proceed with caution, saying there are valid scientific reasons as to why rapid-antigen tests have yet to be introduced to New Zealand.

He says a rapid antigen test is markedly less sensitive than its PCR counterpart, making it less reliable in detecting COVID-19.

"Rapid antigen tests are less sensitive than the PCR tests that have been used in New Zealand to date. We have been pursuing an elimination strategy and that has required the most sensitive tests so we don't miss cases… As such, rapid antigen testing hasn't formed a part of our response," he told The AM Show on Thursday morning.

"There are hundreds of these tests out there and they have very variable performance. The best ones can be about 80 percent sensitive compared to PCR, but many of them perform a lot worse."

Associate Professor James Ussher.
Associate Professor James Ussher. Photo credit: RNZ

He says so far, rapid antigen tests haven't been "fit for purpose" in New Zealand due to the Government's commitment to its 'zero tolerance' strategy, which requires a highly sensitive test to ensure no cases are going undetected. 

But as the Government gradually shifts away from hardline elimination methods to a more suppression-based approach - with both Prime Minister Jacinda Ardern and COVID-19 Response Minister Chris Hipkins saying a return to zero cases is unlikely - rapid antigen tests could play an important role in the future, Ussher says, for surveillance and reassurance.

"They haven't been fit for purpose for use in New Zealand. With a move to transition to living with COVID, there's going to be an important role for [rapid antigen tests] to play, but I think we need to be careful to make sure we get good quality tests into New Zealand and they're deployed in the right fashion," he told The AM Show.

"I can understand the desire of businesses to ensure continuity of business through regular screening of employees, however we need to make sure we've got appropriate processes in place before using these. An important thing to remember... a positive test needs to be appropriately followed up, because it would be more likely at this present time that it would be a false positive."

COVID-19: Expert warns business coalition calling for rapid antigen tests to proceed with caution due to unreliability
Photo credit: Getty Images

He says the primary risk is missing positive cases, which becomes particularly risky in hospital environments. Another issue is that rapid antigen tests are more likely to present a false positive - so any positive result would need to be followed up with a PCR swab to confirm whether the individual is infected or not. 

In its announcement on Wednesday, the coalition emphasised the tests would not take the place of existing PCR tests for border workers or those who are experiencing symptoms.

"There is the risk of missing true infections and that's particularly relevant in patients admitted to hospitals who have symptoms, in which case you really do need the most sensitive test - a PCR test. But there's also the issue of when you're doing screening in a population with a very low chance of having it, that any positive is more likely to be a false positive," Ussher said.

"You need to have processes in place to ensure appropriate follow-up - it's critical anyone who has a positive rapid antigen test has a PCR test to confirm they really are infected… ideally those results are notified to Public Health. So there's a few logistical issues that really need to be sorted."

The coalition of 25 companies, which are looking to procure 370,000 tests via medical supplies wholesaler and distributor EBOS Healthcare, has written to the Government seeking emergency clearance to import the tests within the next seven days. 

Foodstuffs North Island CEO Chris Quin said the company was focused on keeping its team and customers safe and rapid antigen testing would provide a quick and easy way for key staff to test themselves frequently at home or at work.

"COVID-19 isn't disappearing any time soon. We want access to fast testing to provide an additional layer of screening for our essential workforce, who have been hugely co-operative in doing the right thing for each other and New Zealand from a health and safety perspective," he said.

During Wednesday's 1pm press conference, COVID-19 Response Minister Chris Hipkins said while he expects rapid-antigen tests will become available soon, he thinks the coalition's aim is "unrealistic" within the next week.

He said he understands their motivation but indicated it would be unlikely for the Government to grant emergency clearance for the importation within the next seven days.

"Rapid testing will become a bigger part of our response fairly soon," he said.

The 25 companies requesting urgent approval to introduce the tests at critical worksites include Mainfreight, Foodstuffs North Island, Genesis, Hynds Pipe Systems, Mercury, Summerset Group, Wellington Airport, Christchurch Airport, Sky NZ, Queenstown Airport, Spark, Vodafone, The Warehouse Group, ANZ Bank, Contact Energy, Fulton Hogan, Woolworths NZ, Fletcher Building, Chorus, Carter Holt Harvey, Meridian Energy, DHL Express NZ, Air NZ and Auckland Airport.