Risk of incorrect results from rapid antigen Covid tests

More people are buying over the counter rapid Covid tests but experts say there is a big difference to the original PCR checks.

Experts are warning people to make sure they strictly follow the directions for use for Covid home rapid antigen tests or risk getting inaccurate results.

As Covid-19 becomes a part of our long-term daily lives, rapid antigen tests (RATs) are increasingly available over the counter.

Since the Federal Government approved the sale of RATs in Australia on November 1, they have become a common feature of supermarkets and chemists as more people swap drive-through clinics for at-home testing.

But with the accuracy of the tests ranging from 50 to 90 per cent, experts are urging users to do their research on different brands and follow the instructions if they want certainty about their results.

People have been warned to follow the directions of a rapid antigen Covid test. Picture: Tim Hunter

While RATs boast results within minutes compared to hours to days with PCR (polymerase chain reaction) testing, they are much less accurate than standard PCR tests, according to infectious disease expert Professor Robert Booy.

“The sensitivity ranges from 50 to 90 per cent," he said. “The lower rates are a combination of the test not being as sensitive as PCR testing and also user error and the fact the user develops skill in doing it repeatedly.”

Therapeutic Goods Administration (TGA) approved tests are the only ones sold in Australia and range in accuracy from 80-95 per cent.

Tests sold at Coles and Chemist Warehouse are 90 per cent accurate, while those that are 95 per cent accurate usually have to be purchased online. Some with 80 per cent accuracy are known to be among tests sold at other outlets including Blooms.

Despite the different rates of accuracy, the price of the tests doesn’t differ greatly between products, costing around $15 for a one or two pack.

Closely following the instructions of each test kit, repeated use and only purchasing TGA-approved tests sold in Australia can increase the accuracy of the results, according to Professor Booy.

“Although one test might not be as good as PCR if you’re using the test repeatedly, you can improve the sensitivity to more like 70-90 per cent,” he said. “The best thing people can do is follow the instructions carefully.”

The best way to get an accurate result is to follow the instruction manual of the individual test. to the letter.

You will either take a swab from your nostril or throat which will then be placed into an extraction tube and onto a test cassette – much like a pregnancy test. According to NSW Health, if your result is positive, you must get a PCR test as confirmation.