Over the past few months, there has been an expansion of the use of rapid antigen testing (RAT) for COVID-19 in Australia (TGA 2021a).
With these tests becoming more prevalent, it’s important for healthcare workers to have an adequate understanding of this testing method so that they can perform it themselves and supervise others.
What is Rapid Antigen Testing (RAT)?
Rapid antigen testing (RAT) is a type of test used to identify potential COVID-19 cases among people who are not displaying symptoms of the virus (NSW Gov 2021).
RAT involves swabbing the nose and then placing the swab in a chemical solution (NSW Gov 2021). It works by detecting and reacting to proteins (antigens) on the surface of the COVID-19 virus (ABC News 2021).
In Australia, RAT is currently used at:
Aged care facilities in high-risk Local Government Areas (LGAs) of concern in New South Wales.
(NSW Gov 2021; DoH 2021)
Note that home testing is not allowed in Australia (TGA 2021a).
What is the Difference Between RAT and PCR Testing?
There are two types of COVID-19 tests used in Australia: RAT and polymerase chain reaction (PCR) testing.
RAT is a screening test, while PCR is a diagnostic test (NSW Health 2021).
PCR testing, which works by detecting the presence of SARS-CoV-2 viral ribonucleic acid (RNA), is the gold-standard method of COVID-19 testing in Australia (TGA 2021b).
However, unlike PCR testing, which usually takes up to 24 to 48 hours to return results, RAT is able to provide a result within 10 to 15 minutes (NSW Health 2021).
RAT is able to detect potential COVID-19 cases in the acute stage of infection, particularly in the week before the onset of symptoms, and the first week of symptoms (TGA 2021).
Due to being quick and easy to perform, RAT is a useful method of screening employees and students several times within one week (NSW Health 2021).
However, while RAT can detect most cases of COVID-19, it is less accurate than PCR testing and positive results require confirmation via PCR (NSW Gov 2021).
Generally, RAT is considered to be most beneficial when there is a high prevalence of COVID-19 in the community. However, when COVID-19 is less prevalent, the risk of a false-positive result outweighs the potential health benefit to the public (NSW Health 2021).
Who Can Perform a Rapid Antigen Test?
Unlike PCR testing, which must be performed by an appropriately trained health practitioner, RAT can be performed by members of the general public (Covid.gov.cz 2021).
However, non-health practitioners must be supervised by a health practitioner, medical practitioner or paramedic while performing the test, and must be appropriately trained in using and interpreting the test (TGA 2021a).
What Does a Rapid Antigen Testing Kit Contain?
A RAT kit should contain:
A swab inside a sealed wrapper
An extraction vial holder
An extraction vial
An extraction buffer sachet
A test strip
A waste bag.
How to Perform a Rapid Antigen Test
Note: RAT is not appropriate for people who are symptomatic, or those who have been identified as close or casual contacts of COVID-19 cases. These people must undergo a PCR test (NSW Health 2021).
Always follow your local policies and procedures when performing a RAT.
Clear, clean and dry an appropriate flat surface for the test kit to be placed on.
Perform hand hygiene.
Take the test strip out of its foil pack and place it on the cleaned surface. Note that the test must be performed within 30 minutes after opening it.
Twist or snap open the extraction buffer sachet. Take care not to spill any of the fluid inside.
Open the extraction vial and pour all of the fluid from the extraction buffer sachet into the extraction vial.
Close the extraction vial cap and place the extraction vial in the extraction vial holder.
Confirm the patient’s details and gain their consent to perform the test.
Instruct the patient to blow their nose before taking the sample, as excess mucous or blood can interfere with the results.
Perform hand hygiene.
Remove the swab from its packet. Do not touch the soft fabric tip of the swab.
Ask the patient to tilt their head back.
Insert the soft tip of the swab into the patient’s nasopharynx, or until you feel resistance.
Gently rub and roll the swab three to five times, staying parallel to the patient’s palate.
Slowly remove the swab and offer a tissue to the patient.
While still holding the swab, pick up the extraction vial and open the lid.
Peel back the foil of the extraction vial and place the fabric tip of the swab inside the vial, into the fluid.
Record the time of the sample collection.
Rotate the swab five times in the extraction vial.
Lift the swab and squeeze the extraction vial to drain the remaining fluid from the tip into the vial.
Break the swab at the breakpoint and discard the top half into a clinical waste bin (note that some products may be different).
Tightly press the nozzle cap onto the extraction vial to prevent leakage.
Gently squeeze the extraction vial, placing three to five drops of fluid into the specimen well marked ‘S’ on the test strip. Ensure you are dropping fluid, not an air bubble.
Discard the extraction vial into a clinical waste bin.
Record the time when the sample was added to the test strip.
Wait 15 to 20 minutes, or until the test strip shows a clear result.
One line next to the ‘C’ on the test strip means the result is negative.
If there are two lines, the result is positive.
If there are no lines visible, or one line next to the ‘T’ on the test strip, the test is invalid and the patient needs to be tested again.
If the patient gets a positive result, they must get a PCR test to confirm their result and follow all isolation requirements.
Ensure all test contents are appropriately disposed of.
If you are going to test another patient, clean the surface and perform hand hygiene before performing the next test.