A person wearing personal protective equipment holding up a SARS COVID-19 rapid antigen test swab

Who is to blame for RAT false negatives — manufacturers or the people using them? Here’s how you should be taking a RAT

While PCR tests are still available and remain the “gold standard” for testing, many have turned to rapid antigen tests (RATs) out of convenience or as part of a requirement to return to work or school.

They can provide results within minutes, don’t require a healthcare worker or lab to process, and help to catch COVID-19 cases that otherwise would have gone undetected.

But with these benefits comes a range of limitations – the biggest one being that they can provide false negative or false positive results.

Recently, some doctors have warned people against relying on a negative RAT result.

Meanwhile, the makers of RATs have hit back, blaming false negatives on a lack of education about how and when to properly use the tests.

So is there any evidence that indicates the effectiveness of RATs has been impacted? And does it have to do with people using them incorrectly?

Australia faces ‘an education gap’ that was ‘never filled’ after RATs went on the market

Pathology Technology Australia, the peak body for test manufacturers and suppliers, defended the performance of rapid tests against new variants of Omicron, accusing critics of “farmongering”.

“Nothing has changed, we’re yet to see any evidence that clearly indicates performance has been impacted by the subvariants,” chief executive and clinical biochemist Dean Whiting said in a statement.

“There is an education gap in Australia that was never filled after RATs became available.”

“I think a lot of the false negative results are due to incorrectly collecting the sample,” Mr Whiting said.

Here are the essentials to taking a RAT.

Store the test at 2C-30C

The Therapeutic Goods Administration (TGA) warns that tests “may not work properly” if they have been exposed to excessive light or heat, or if the packaging is damaged.

The instructions for a RAT specifically say to store it in a cool, dry place at 2 degrees Celsius up to 30C.

Do not freeze the kit and do not store it in direct sunlight.

Check the expiration date

According to the TGA, RATs can be stored for 12 months from the date of manufacture.

Do not use the test after its expiration date.

Blow your nose

David Speers, a clinical microbiologist and head of the microbiology department at PathWest, told ABC Radio Perth this will clear any excess mucous so that it won’t interfere with the results.

“What you want to do is sample the lining of the nose — you’re not sampling the secretions as such,” he said.

Only open the kit right before use

If you open the kit components, don’t suddenly delay taking the test and leave it out until you decide to.

When you open the kit, take the test straight away.

Don’t contaminate the test

Whether it’s with your fingers or your kitchen tiles after dropping it (there’s no five-second rule here), the tip of the swab should not touch anything.

So make sure it doesn’t come into contact with any other surfaces.

Swabbing at the wrong angle and depth

You’ve made it to the hardest part.

It’s easy for many to get the angle or depth wrong when it comes to swabbing.

Mr Whiting said he has seen many people wave the swab around the inside of their nostrils when taking a RAT.

“This is not the way the manufacturer intended for you to use the test,” he said.

“The manufacturer intended you to put the swab at least 1.5cm up your nose and swish it around five times, then do the other side.”

A guide published by the Public Health Laboratory Network (PHLN) and the Department of Health says to insert the swab tip 2cm to 3cm into each nostril.

The key is to insert the swab all the way up your nostril until you feel it rub against the back of your nose.

Watery eyes and the urge to sneeze indicate you’re taking the test correctly. (Supplied: John Hopkins Medicine)

Rather than going directly upwards with the swab, make sure the swab passes horizontally.

Then rotate the swab gently against the walls of the nasal passage five times, for 15 seconds in each nostril.

“You will know when you’re doing this correctly because it’s slightly uncomfortable,” Mr Whiting said.

“If your eyes aren’t watering or you’re not resisting the urge to sneeze, then you’re not taking the sample correctly.”

Swirl the swab in the tube for 10 seconds

Hold the solution tube firmly with one hand.

Once you’ve inserted the swab into the tube, swirl it around in the fluid for 10 seconds.

Then pinch the swab tip through the tube to remove any remaining fluid.

For some testing kits, you will need to snap the end of the swab. The swab will indicate where to do this.

Don’t add too many drops to the device

Remove the test device from its protective package and place it on a well-lit, flat surface.

Keep the tube vertical with the cap pointed down.

Squeeze five drops of liquid from the tube into the well on the device.

Adding too many drops or too few will affect the timeline and the test will be inaccurate.

Follow the no earlier than 15, no later than 20 rule

Keep the test device on a flat surface.

Read the result at 15 minutes.

Do not read it earlier than this, or after 20 minutes.

After 20 minutes, the result might become inaccurate.

Misreading the result

  • Two lines mean you have tested positive for COVID
  • A line at C only means you have tested negative and you do not have COVID
  • A line at T but not C means your test is faulty
  • No lines means your test is faulty
Four COVID-19 Rapid Antigen Tests showing all possible test results
Your RAT result will look like one of these.(Supplied: Antibodies.com)

Dispose of the kit correctly

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