Editorial: RATs have limits but we may have no choice

A person holds a negative result of the Covid-19 antigen rapid test in Edmonton, Alberta, Canada. Photo / Artur Widak via Getty Images, File

EDITORIAL

If, as expected, cases of Omicron rise to the thousands in New Zealand then self-isolating and home tests will come more into play.

The opposition has repeatedly called for immediate deployment of rapid testing kits to offer more individual control over monitoring for the presence of the virus.

National's health spokesman Chris Bishop said this month: "Widespread availability of rapid Covid tests must be part of the toolkit alongside nasal and saliva-based PCR tests. Under Omicron, testing will be more important than ever.

"The Government must make sure we have a good stock of rapid tests in New Zealand and it needs to liberalise the rules around their use."

One big issue is supply. National Party leader Christopher Luxon told RNZ the 4.6 million rapid antigen test kits (RATs) in the country was "alarmingly low" and the Government should have acted sooner to stockpile them and authorise private importing.

However, Covid Response Minister Chris Hipkins said there were widespread international issues with supplies. "Countries that are relying on them are now running out," he said.

He pointed out the Government began efforts to buy as many as possible before Christmas. "We know that as this situation unfolds we're going to want to use rapid antigen testing a lot more."

It does appear the Government has been leery on endorsing RATs and there is a case for reluctance - it seems rapid doesn't always mean optimum results.

One, albeit small and preliminary, US study found RATs for Covid-19 may not reliably detect the Omicron variant during the first few days of infection, even when a person is shedding the virus in high enough quantities to be contagious, preliminary evidence hints. The viral load is highest, producing greatest transmissibility, in the three days after infection.

The concern is the tests might yield false negatives, especially early in the infection. There is some speculation that swabbing the throat in addition to the nose may be more accurate.

Despite the concerns, Australia has increasingly thrown more of its pandemic response into RATs. This week it announced international air travellers can enter the country if they provide results from a RAT taken within 24 hours of departure. This replaces the former policy of a negative PCR result within three days of departure.

Health Minister Greg Hunt says the move recognises "the global reality of a more infectious but less severe strain and the challenge that it has created internationally in terms of access to PCR tests".

However, that's not yet a reality for New Zealand and we should continue to pursue the most reliable means of testing for as long as possible.The Government has recognised this by boosting capacity to process up to 78,000 PCR tests a day, while stepping up a stockpile of RAT kits.

Much more of a priority right now is to become more proficient with wearing properly fitted masks. Slowing the spread will give our PCR processors time and space to get results by the method described by the US Centres for Disease Control and Prevention as the "gold standard".