Covid-19 Omicron outbreak: How to do a RAT (rapid antigen test). Video / Gary Payinda
Rapid antigen testing (RAT) is the new normal in Covid swabbing and stocks of RATs are flying off shelves across Northland retailers.
But the self-service tests have faced scrutiny over their accuracy, so how can you get the most out of your RAT?
Northland District Health Board emergency medicine specialistGary Payinda uses RATs regularly on the job. He explained why they have replaced PCR testing.
"Essentially, RAT tests are like the quick and dirty tests that replace the more invasive, much more uncomfortable nasal pharyngeal swabs that go all the way along the base of your nose almost to the back of your throat."
Payinda said the efficiency and self-service of RAT tests helped ease the strain on the healthcare system as cases climbed during the Omicron outbreak.
"The benefit of the old PCR tests was that they were extremely accurate. But the downside is the discomfort and also the delay it took. In some cases hours, like if you're being tested as a hospital patient, but in most cases days to get your result back.
"With as many cases around now, that is impractical and very expensive. Whereas the RAT tests are less accurate but much faster and much cheaper."
"In any test that has about 12 steps, you can virtually guarantee that there are going to be lots of people who do some of the steps wrong."
At present, there are 11 different types of RATs approved for use in New Zealand - each one has a slightly different set of instructions and methods.
"The best advice I can give is read the instructions and spend five minutes before you do this RAT making sure that you understand all the steps."
Self-service rapid antigen tests have replaced the gold standard PCR tests, but there are a lot of things that can go wrong when taking a RAT. Photo / Chris Weissenborn
Payinda said some people have been confused because they have tested negative while living with someone who tests positive.
This can come down to symptoms and that one RAT is not enough to rely on, he said.
"Rapid antigen tests are most useful in people who have a really high viral load, and a lot of the time but not always that's going to be people who are highly symptomatic.
"That's the worrisome thing for me, asymptomatic people letting down their guard with a RAT that's negative."
There's a reason those RATs come in packs of five, Payinda explained. RATs are good for "frequent and repeated testing" and "the more tests you do, the more you can count on it".
The accuracy of RATs also varies between brands. The Northland DHB currently provides Zhejiang Orient Gene Pkt5 rapid antigen tests.
On the instruction manual, the Orient Gene RAT says it is 97.25 per cent accurate at identifying Covid-19 positive samples.
But studies on RATs show that sensitivities of the tests can greatly range depending on how infectious you are.
This is why it is important to test on day three and day seven of self-isolation if you live with a person Covid positive because testing sooner may produce false-negative results.
"These are good, but not perfect tests," said Payinda.
Northland DHB Covid Programme senior responsible officer Jeanette Wedding described what Northlanders can expect when they want a Covid test.
"Northlanders should go to a testing station with an order via the requestrats.covid19.health.nz website when they are symptomatic or a household contact."
Northlanders can order RATs for their entire household but how many tests you will receive depends on your family size, Wedding said.
"They are eligible to three RATs per person. However, pack sizes are currently five RATs per pack and entire packs are handed out – they will be rounded to the nearest pack based on three per person.
"One person in a household will get one pack - five RATs - five people in a household will get three packs – 15 RATs."
People wanting a RAT who are not unwell or a household contact must buy one from a retail store.
"RATS are free under the public health response for those who need a test; household contacts and people with symptoms," Wedding said.
RATs have been provided by the Ministry of Health to critical workers working directly with Covid cases and contacts.
These workers include the emergency services and healthcare workforce; and high-density vulnerable population providers such as hospice.
Northland businesses outside of the critical services groups have to purchase their own RATs if they want to test workers.
