14 Dec 2021

Rapid antigen testing: What you need to know

12:14 pm on 14 December 2021

As regional boundaries lift from 15 December, some unvaccinated domestic travellers will have to get rapid antigen tests as part of the Covid-19 Protection Framework requirements.

One of these will be either providing proof of a Covid-19 vaccine pass, or proof of a negative test.

On 9 December, the government announced details on rapid antigen testing for domestic travellers.

The rules come into force when the domestic regional boundaries lift (on 14 December 11.59pm to be more precise).

But what is the rapid antigen test?

Who will be required to get it and who will need the PCR one? What is the difference?

How accurate is it? Will it be rolled out further?

RNZ is here to clear it all up with input from the experts.

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Photo: 123RF

Who can get the rapid antigen test for free?

The rapid antigen test will only be available for those meeting certain criteria:

  • Unvaccinated
  • Over 12 years old
  • Asymptomatic
  • Requiring the test for the purpose of departing Auckland region (including Port Waikato), or requiring the test due to an airline or ferry's rules for passengers

The Ministry of Health said it will be free of charge for people who meet the above criteria, from when the regional borders lift until 31 January 2022.

It is only for asymptomatic people because the health advice for symptomatic people, regardless of vaccination status, is to stay home and get a PCR test.

Unvaccinated workers who were already part of a testing regime for crossing the Auckland boundary could continue with their current regime, the ministry said. Other unvaccinated workers can use the negative test within 72 hours.

While domestic travellers are still able to use PCR testing, health officials hope this option will free up capacity at laboratories so they can focus on processing PCR tests for symptomatic people and close contacts of confirmed cases.

People who break the rules face fines of up to $1000, and police will have discretion on enforcing these rules.

What is the rapid antigen test? How is it different to the PCR test?

It is described as a point of care testing that is a "less invasive nasal swab" than the PCR test, according to Pharmacy Guild chief executive Andrew Gaudin.

Deputy chair of the NZ Microbiology Network, which is facilitated by the Institute of Environmental Science and Research, Juliet Elvy told Nine to Noon the upside of the antigen test was that it was quick and simple.

"The con is ... that the sensitivity of the test is much less than a traditional gold standard PCR test.

"In fact, they performed best in people at the start of the infection, where they are expected to have a very high viral load, and that's usually within the first five days of infection."

It can be useful to screen for infection in asymptomatic individuals, but the lower sensitivity does mean those with low viral loads or in the pre-symptomatic phase may be missed, Elvy said.

"But one way to mitigate that reduction in sensitivity is to actually perform the rapid antigen test more frequently so that you increase the likelihood of detecting that point at which that person does become infectious with a viral load that's detectable by the rapid antigen."

Where can I get the rapid antigen test?

The test will be available at some community pharmacies across the country, which be listed on the Healthpoint website.

A 'supervised rapid antigen testing for travel' section will be updated on the site, which will allow you to filter for you region and find a pharmacy that offers rapid antigen testing.

Once you're there, pharmacies will confirm your eligibility as set out above and collect some key information, like verbal consent to the test and your mobile phone number to send your result.

"The tests will be prepared, undertaken and supervised by a community pharmacy staff member who's been trained, and the individual will be supervised during their own nasal swab," Pharmacy Guild boss Andrew Gaudin told Nine to Noon.

Once you're done, the pharmacist will put your sample to the test, insert the result into the system, and advise you of the result.

"The individual will be able to leave after the test is completed and they'll get a text from the system to confirm whether they've got a negative result and if they don't have a negative result, they'll be getting a call from their pharmacist about what happens next."

You've got the all clear, or not, what next?

A negative rapid antigen test result will appear as a text on your phone. Gaudin said that should be the proof for officials to confirm your test result for when you need to travel domestically.

"They'll see that you've got a proof of the right text, from the right number with the right details. And all you have to [do is] simply show that text to those people who ask for it.

"Obviously those who've got vaccine passes won't need this."

However, if you receive notice from the pharmacy of a positive result, then you must isolate and immediately take a PCR test at a dedicated station or centre and wait for the result.

How long before departure should the rapid antigen test be taken?

The negative test result will need to be presented within 72 hours before departure, otherwise you must take another one.

The ministry has strongly recommended the antigen test be taken as close as possible to the time of travel, preferably within 24 hours before departure, with the turnaround time for a result just 15 minutes.

When the regional boundaries lift, Air New Zealand and Interislander will also require asymptomatic passengers over the age of 12 to show proof of a vaccine certificate or a negative test, regardless of where you are in the country.

Interislander said there would be no charge for anyone re-booking because of a Covid-19 test.

There will also be spot checks for travellers out of Auckland Airport.

How accurate is the rapid antigen test?

It is also possible there could be an invalid test, in which case you will need to have another rapid antigen test and if that turns out to be inconclusive, you will then need to get a full PCR test, Pharmacy Guild boss Andrew Gaudin said.

NZ Microbiology Network's Juliet Elvy said the antigen tests that are being utilised have a very good specificity, but potentially one or two out of every 100 tests might yield a positive result unexpectedly.

"Whilst we have very low rates of Covid in the community, that would mean that those one or two people that have yielded a positive test have a much more likely chance of it being a false positive.

"That's not the same as saying, you know, two out of every five tests performed will be false positive.

"The majority of these tests should hopefully yield a negative result. But of the ones that [get the] positive, then there is a high chance that those ones are false positives, so not true positive."

Can anyone else get the rapid antigen test?

The Ministry of Health has said people will not be able to purchase a rapid antigen test from pharmacies to complete the test at home, but that is under consideration and it may become available for the general public in the New Year.

They have already been introduced at Middlemore, Auckland City and North Shore hospitals.

Twenty-nine large businesses, including airports, energy producers, food manufacturers and retirement homes, have been trialing rapid antigen testing since October.

The lower sensitivity of the antigen testing was one of the reasons why we should be cautious about rolling it out further, Elvy said, especially without higher numbers of Covid-19 cases.

"The concern is false positive results that yield results that are inconvenient for people who will then have to self-isolate while waiting a PCR confirmation and that PCR confirmation absolutely must take place. Because we don't want to be falsely diagnosing Covid in people that actually don't have the disease," she said.

"One of the major problems with widespread home usage is that the data capture for those tests being performed is not robust," which would be crucial to understand how the tests were being used, Elvy said.

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