EXPLAINER

When to use a rapid antigen test to diagnose COVID-19

Changes to the definitions and requirements for close and casual contacts, and requirements for interstate travel, has made rapid antigen tests a hot product in the ACT.

So when should you use a rapid antigen test, and what happens if you get a positive result?

What is a rapid antigen test?

Rapid antigen tests are over-the-counter COVID tests which can be used at home.

Using them involves taking samples from the nose or saliva, mixing the sample with a fluid and putting drops of the fluid on a small device.

One red line appearing on the device indicates the test is clear of COVID and two red lines indicates infection. The results appear within 10 to 30 minutes.

"These tests are not as accurate as a PCR test but you do obtain your result in a much quicker time frame," the ACT Health website says.

The higher the viral load, the more accurate the rapid test will be. This means it is less accurate in the early and late days of infection. When symptoms have developed, the rapid test gets it right almost every time.

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What is a PCR test?

A polymerase chain reaction (PCR) test is the one you get at a testing site.

In the ACT, they can only be performed by trained healthcare workers at an ACT government, or private pathology, clinic.

A sample of fluid is taken from the back of the throat and inside each nostril. The results are analysed in a lab, and then texted to the patient.

"PCR tests are the most accurate way to confirm if a person has COVID-19 and results usually take 24 to 48 hours," ACT Health said.

When should I get a rapid antigen test?

PCR tests are the only results which are accepted as a formal diagnosis of COVID-19. So if you have any COVID-19 symptoms, or are a close contact, you must get a PCR test.

Casual contacts are advised to either monitor for symptoms, and can take a rapid antigen if they want to and do not have any COVID-19 symptoms.

ACT Health have also started using rapid tests for day-one and day-six tests for identified close contacts of a confirmed COVID-19 case.

A negative result from a rapid test is sufficient to travel interstate to Queensland from the ACT (within 92 hours of taking the test) and Tasmania (within 24 hours).

All arrivals in the Northern Territory are now required to undertake a rapid antigen test within two hours of arriving in the Northern Territory.

All arrivals are still required to undertake a rapid antigen test on day three and day six after arriving in the NT.

There is no negative test result required to travel to NSW, Victoria or South Australia from the ACT. To travel to WA, Canberrans must get prior permission and quarantine for fourteen days on arrival.

Rapid antigen testing kits have become a very hot commodity in Australia. Picture: Dion Georgopoulos

Rapid antigen testing kits have become a very hot commodity in Australia. Picture: Dion Georgopoulos

Where can I get a rapid test?

Antigen tests are sold across Canberra in many pharmacies and supermarkets.

There is a lack of supply of rapid antigen tests across the ACT and NSW at the moment.

Many retailers are often sold out in the morning, if they are even in stock in shops.

A lot of shops and chemists have instated purchase limits to prevent people stockpiling the tests.

One rapid antigen test will cost about $15, with nasal tests generally costing less than the saliva-based tests.

Many pharmacies are only selling the tests in packs of five, which are priced around $60.

What happens if I get a positive antigen test result?

Anyone who receives a positive antigen test result must get a PCR test as soon as possible. You will be considered high priority for a PCR test.

Only PCR tests are accepted as a formal diagnostic test or as proof of COVID-19 status - both negative or positive.

If you have symptoms or are a close contact, and returned a positive rapid test result, you must get a PCR test immediately.

You should then isolate at home until you receive your PCR result.

This story When to use a rapid antigen test and where you can buy one first appeared on The Canberra Times.