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Rapid antigen tests get the go-ahead – Expert Reaction

A green light for rapid antigen testing and wider saliva testing are among large-scale changes to the country’s Covid-19 testing approach.

Rapid antigen testing – which can detect the virus in 15 mins – will be piloted in Auckland and Christchurch, beginning soon in Auckland hospitals. This follows a review of the nation’s testing strategy that highlighted the need for more agile, tailored testing.

The SMC asked experts to respond.

Associate Professor Siouxsie Wiles, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, comments: 

“Restricting the importation of rapid tests was a necessary step at the beginning of the pandemic because so many of the tests were extremely unreliable and their use was not compatible with us pursuing an elimination strategy. In the time since, there has been a lot of innovation in this space and their reliability has improved.

“Using rapid antigen tests to complement our PCR testing will be important as we transition from elimination to high suppression as our COVID-19 strategy. What everyone must remember though is that these tests are not a panacea.

“While they give a result very quickly and so can be deployed in a range of scenarios, a recent review shows that depending on the test, they can still miss 2 to 3 out of every ten COVID-19 cases in people with symptoms, and 3 to 6 out of every ten cases when the person has no symptoms.

“I am relieved to hear the government will work with industry representatives to look at where the use of rapid tests will add value to keep people safe from COVID-19. This should be extended to other sectors where these tests can play an important role, such as in ECE and school settings.”

No conflict of interest.

Professor Michael Plank, Te Pūnaha Matatini and University of Canterbury, comments:

“The introduction of rapid antigen tests is very welcome news. Hopefully these tests will soon become more widely available and regularly used. They aren’t as sensitive as the “gold standard” PCR tests which means they will miss some cases, especially those with low viral load or people who are tested early or late in their infectious period. However, they have some key advantages over PCR in specific applications.

“For people who need to be tested regularly, some combination of rapid antigen tests and saliva PCR tests can be done more frequently than the traditional nasal swab. This will catch more cases earlier than a weekly PCR test.  A weekly PCR test is not much use if someone is tested on a Monday and gets infected on a Tuesday because it’s too long until their next test.

“Rapid antigen tests can also be used to provide an on-the-spot result for people before they enter workplaces, large gatherings, flights, or high-risk settings such as hospitals. They shouldn’t be relied on to catch every case, but they can significantly reduce risk especially if combined with other measures such as vaccine certificates and masks.

“Rapid antigen tests are not a replacement for PCR but will be a very useful addition to our testing system. As community transmission of Covid-19 becomes more widespread, we need to get more used to regular testing as an ongoing measure to manage the spread of the virus.”

Conflict of interest statement: I am partly funded by MBIE for research on mathematical modelling of COVID-19.

Lesley Gray, Senior Lecturer, Department of Primary Health Care & General Practice, University of Otago, comments:

“I have been calling for rapid antigen testing (near person testing) for some time now. It makes sense in the overall surveillance to detect COVID-19 to complement the more formal ‘gold standard’ nasal PCR testing.

“We have seen in just the last week or so how surveillance testing has picked up a number of otherwise undetected cases at routine hospital and truck driver testing.

“Many countries have adopted a range of tests for use in different settings and circumstances. Accuracy of results varies in all tests. Nasal and Saliva PCR tests are the most accurate. Home-based antigen tests vary, with some giving as low as 50% accuracy of result. Many self-tests have a role to play, but can give false positive as well as false negative results.  Lab testing with trained professionals can bring an accuracy of between 76% to 89%, and can drop to as low as 50% in ‘real world’ situations.

“Rapid, quick tests for surveillance have their place, and are especially good for detecting people with high viral loads in the early phase of disease, usually in the first week of infection. Anyone with any symptoms, or concerned they may have been in close contact of a case, should contact their health provider to seek a PCR test, and self-isolate until receiving a negative result.”

Conflict of interest statement: “Note: Lesley has received a Health Research Council grant for this research: “Improving effectiveness and equity in the operation of COVID-19 ‘self-isolation'”

Dr Dianne Sika-Paotonu, Immunologist, Associate Dean (Pacific), Head of University of Otago Wellington Pacific Office, and Senior Lecturer, Pathology & Molecular Medicine, University of Otago Wellington, comments:

On testing:

“The introduction of saliva testing and rapid antigen testing for hospitals, schools and workplaces to support COVID-19 testing regimes over the next months, is welcome news.

“The utilisation of these testing methods are much needed at this time given the presence of Delta in our communities already, and with our vaccination levels sitting at ~50% for those fully vaccinated.

“The announcement also to extend the Waikato border beyond the current Alert Level 3 boundary and shift this further south, is a smart move given the new COVID-19 cases in the Waikato and other recent developments.

“We’re continuing to experience first-hand how quickly and easily Delta can spread and infect people, with vaccination critical for keeping everyone protected from COVID-19 – especially our most vulnerable.

On vaccination:

“Increased COVID-19 vaccination efforts that have resulted in improved vaccine accessibility, and vaccination rates for Pacific peoples, include Pacific-targeted and tailored events and activities, that have been Pacific-led and community driven, working together with Pacific health providers.

“These Pacific-designed and led strategies work because they have an equity approach that is focused on getting help and services to those who need help, in a way that builds trust and reduces barriers for them – in this case the COVID-19 vaccines.

“The best way to protect our children who currently don’t yet have access to a vaccine approved for them, is for everyone around them to get vaccinated. Ultimately, vaccination levels within Aotearoa New Zealand must increase to keep everyone safe from COVID-19 – including our most vulnerable. Only 3% of those involved in the current outbreak had been vaccinated.

“Get vaccinated, get tested, follow the alert level rules and reach out to others around you to do the same – don’t stop fighting COVID-19.”

No conflict of interest declared.