Everything you need to know about rapid antigen COVID-19 tests

With the spread of the highly-transmissible omicron variant, Australia has reached over 2.7 million active cases around the country.
This situation and the current self-isolation policies have been counterproductive to the Australian government’s strategy to reopen its economy after it was decided that the economic cost of keeping Australians locked down was too expensive to bear. But, as people test positive and thus have to self-isolate the difficulty of obtaining a test rises, coordinating timelines to return to work or school after a close contact, for example, has been difficult, leading to what some are calling a “shadow lockdown.”

There is confusion surrounding the two different types of tests available and so with this, the team at MedAdvisor will delve into everything you need to know about rapid antigen tests (RAT).

What is a rapid antigen test (RAT)?

To understand what RATs are, it’s essential to first understand the definition of the word “antigen.” In simple terms, an external substance that leads the body to create an immune response against that substance is an antigen. This can include bacteria, toxins and, of course, viruses. 

The advantage of RATs and the reason they are so popular is their convenience. Individuals can test whether they have contracted COVID-19 within the comfort of their own home and without a physician present. RATs also typically display test results after 15-30 minutes. RATs can also sometimes detect COVID-19 within someone’s body before symptoms arise.

The way these tests check to see whether you have contracted COVID-19 is to see whether any of the coronavirus proteins are present in your body by checking the points at which we humans leave viral particles (like the nose and mouth). Blood tests are not the best tests to check whether you have contracted COVID-19 because antibodies can take a while before showing up in a blood sample. But, individuals infected with the virus are most infectious early on.

How accurate are rapid antigen tests?

According to the Victorian government website, RATs are very accurate “when used by people with symptoms or COVID-19 contacts.” More specifically, RATs can detect whether you have contracted COVID-19 during what’s known as the “acute” phase of infection.

But, if you aren’t showing any symptoms of COVID-19 and are not a close contact, but a RATs result comes back positive, you can confirm your result with a PCR test. Although RATs can produce more false positives, The Victorian health department has said that these tests “are likely to find most COVID-19 cases in people with symptoms.”

Home testing, as the first option, is recommended for those with symptoms or who is a close contact.

The chance of a false positive (when the test shows that you have contracted COVID-19, but you haven’t actually) are decreasing. On the other hand, though, there is still a chance of your RAT producing a false negative (showing that you don’t have COVID-19 when you do), and so if you are in high-risk situations, such as working with vulnerable members of our community or are a frontline health worker, you can decrease the chances of a false negative by testing regularly or testing with various brands of RATs. 

The Therapeutic Goods Administration, or TGA, have approved over 20 different types of at-home rapid tests. These tests can be divided into three primary categories depending on their levels of sensitivity; acceptable sensitivity, high sensitivity and very high sensitivity. This is measured by each test's positive percentage achieved from a case confirmed by a PCR test, and the thresholds are 80%, 90%, and 95%, respectively. 

Very high sensitivity tests included the LYHER nasal swab and the OnSite nasal swab.

How do you use rapid antigen tests?

When it comes to using RATs, the TGA urges patients to read the individual test instructions on their specific RATs packet carefully to maximise the chances of accuracy. 

Nasal swab test: 

The materials provided in a nasal swab test include a single-use swab, a test cassette, an extraction tube and a waste bag. It is recommended that you also have a timer or a device with timer functionality, as well as tissues. 

Using the ​​SARS-CoV-2 Antigen Self Test Nasal involves four steps, according to Roche Diagnostics, although it is also recommended that you read your test instructions as well. 

1. First and foremost, before undertaking the test, wash your hands. From there, remove the swab from the packet by the handle, ensuring that the swab is only held by the handle. From there, tilt your head back and insert the swab into one nostril until you feel a slight resistance, at which point, don’t apply additional pressure. Instead, turn the swab four times for a total of 15 seconds inside the nostril and then repeat this with the same swab in the other nostril. 
2. From there, place the swab inside the extraction tube. Squeeze at the bottom, turning the swab back and forth over 10 times to force all the liquid out of the swab. Press the dispenser cap onto the tube. 
3. Place the test strip on a flat surface and hold the extraction tube over the round area. From there, drop exactly four drops onto the field, squeezing the tube if need be. 
4. Set the timer for between 15-30 minutes.

A visual guideline of how to perform a RATs test as well as interpret the results has been provided by the TGA and can be found here. 

Salvia Pen Test: 

The saliva pen test is relatively less invasive compared to the nasal swab, but like the nasal COVID-19 test, there are also several steps involved. 

1. Begin by ensuring you don’t eat, drink, smoke or chew gum at least 30 minutes before the test. Before beginning, also ensure that your hands are clean. 
2. Remove the test from the packaging, take the saliva collector out from the base and remove the protector.
3. Deeply cough four times while covering your mouth. 
4. From there, place the collector on the top, underneath or the side of your tongue for two minutes. 
5. After doing this, take the collector from your mouth and push it into the base. The top edge of the base should be in the middle of the supporting ring.
6. Set the timer for 15 minutes, and don’t read the results after 30 minutes. 

A visual step by step outline has been provided by the TGA here. Or you can watch the below video to see what’s involved and how to do a RAT at home.

Rapid antigen tests vs Polymerase Chain Reaction (PCR) tests

According to Dr. William Schaffner, a professor of Preventive Medicine, Department of Health Policy, and professor of Medicine, Division of Infectious Diseases at Vanderbilt University Medical Center, 

The general public has difficulty in understanding that the interpretation of COVID tests is not a simple positive or negative. It is more complex and depends both on the type of test and the timing of when the test is done relative to the time of exposure.”

One of the primary differences between the two tests is the way the test can be obtained. RATs can be bought over the counter at supermarkets and pharmacies and are primarily purchased so that an individual can test whether they have contracted the virus at home. This is compared to a PCR test, which is administered by a medical professional and typically requires you to line up at approved clinics for a test. These clinics can either be walk-in or drive-in clinics.

Another major difference between the two tests is that PCR tests are more sensitive and thus accurate than RATs. What this means is that it can detect relatively smaller amounts of the virus in your body than RATs can and so can determine whether you’ve caught COVID-19 earlier than an antigen test. Because of this, both a positive PCR and antigen test can be trusted as positive. However, a negative antigen test may need to be confirmed with a PCR test. 

The amount of time required for results to show is also different. For example, antigen tests take under 30 minutes, whereas PCR tests generally take around two days, and you are usually notified via a text message. In the situation that your antigen test comes back positive, you are required to report it. This is compared to a PCR test, whereby positive results are automatically reported.

In terms of which one to use, this depends entirely on your situation. For example, because the PCR test is more sensitive, it can detect bits of the virus, not just the whole virus. This means you may potentially test positive with a PCR test for weeks, even after symptoms have subsided and you’re no longer contagious. This makes it difficult to understand when to end isolation or quarantine and also makes daily life challenging. However, if you’re travelling and require the most accurate results, for example, PCR tests may be required or more appropriate.

On the other hand, because rapid tests are less sensitive, it will likely show a negative test result if you’re only shedding a small amount of the virus, such as in the early days of your infection or after you’ve recovered. Therefore, antigen tests can be helpful to provide assurances to friends, family, work, etc. 

Rapid antigen test supply issues 

One of the big reasons we’ve got those queues in Victoria and NSW is you’ve got people who are required to get PCR tests before they travel into other states. Now, that needs to be looked at,” said Prime Minister Scott Morrison back in December of 2021.

“Rapid antigen testing in those situations would certainly be a more effective option.”

However, although this may be the case, the battle for Australians to get their hands on these antigen tests continues, therefore often leaving the COVID-19 test shelves of distributors, like pharmacies and supermarkets bare. When there is supply, prices have often been pushed to record-highs. 

With this being the case, state governments are working directly with manufacturers to increase RATs supply. In addition, the Australian Competition and Consumer Commission (ACCC) has also made it illegal under newly imposed laws to charge a profit margin above 20% on antigen tests. 

Coupled with these efforts, as of late January, concession cardholders will be eligible for free RATs at participating pharmacies. This is the most recent addition to the already 6.6 million people, from pensioners to veterans to low-income groups, that are eligible for 10 free tests within three months with a maximum of five in one month. 

You must present your Commonwealth concession card at your local pharmacy and provide consent to record these details. The pharmacy will then check these details as well as the number of tests that have already been supplied to you. You will receive a minimum of two tests and can request up to five (the monthly limit) at any one time. 

With the pandemic still in full swing and new variants of concern and interest appearing on the World Health Organization (WHO) radar, we must remain vigilant as individuals and communities when it comes to managing the pandemic. This involves understanding the differences between RATs and PCR tests and when it’s more appropriate to undertake one test over the other. 

Book your COVID-19 (first, second or booster) vaccination with your local pharmacy via the MedAdvisor app. Our network of pharmacies is vaccinating more than 50,000 people a day. We are proud to be supporting this important health initiative with our technology.

If you would like to learn more about the COVID-19 pandemic or are just looking for general coronavirus resources and support, check out this page and our company blog.