You think you may have Covid, but after taking a rapid antigen test, you find that you are still negative despite exhibiting symptoms. What is going on?
The good news is that you are not alone; many people have been reporting dubious test results. The bad news, well … you may actually have Covid.
Prof Alexandra Martiniuk is an epidemiologist at the University of Sydney. She has been receiving countless questions about RATs as cases soar and people scramble to keep their families safe.
RATs have a much lower accuracy than PCR tests, but are still vital detection tools thanks to their accessibility.
“Most are probably around a 75% sensitivity,” said Dr Michael Lydeamore, an infectious disease modeller at Monash University. “Meaning if you have Covid … you have a 75% chance of testing positive. Compare that to PCRs, which are about 99%. So there’s a big gap there.”
He says that the lower sensitivity of the tests isn’t too much to worry about as we enter a new stage of the pandemic, where missing some cases a day will not affect overall health outcomes too drastically.
By avoiding some common mistakes and following some important tips, you can get the best out of your RATs.
Which RAT should I use?
There are many different tests on the market, but not all RATs are created equal.
Martiniuk recommends only using approved tests sold in Australia, as they will have been assessed by the Therapeutic Goods Administration (TGA).
Different brands of RATs have different levels of accuracy. The TGA has a list of all of the approved tests sold in Australia, rated in terms of their sensitivity. A good way to ensure your tests are accurate is by checking the list.
Currently, the TGA supports three types of tests: nasal swabs, saliva and oral fluid. Dr Martiniuk says that there is no “clear-cut pattern” of which test is most effective. She suggests focusing on brand name when looking for the best test.
Most of the tests with a “very high sensitivity” rating tend to be nasal swabs, but some saliva tests also have high rankings.
Did I do my test wrong?
RATs come in different forms, with some being administered through the nostrils and others through the mouth. Martiniuk says one of the most common mistakes people make is not reading the instructions carefully.
Make sure to read the fine print. Most tests provide detailed instructions, including the number of swabs, the method of swabbing (some ask you to spin the swab) and where to take the sample (mouth, nostril, throat).
For nasal samples, low and slow is the motto. If unsure, some pharmacies provide supervised RATs.
Also make sure your RATs are kept in a cool dry place.
My RAT is negative, but I am sure I have Covid
If you have symptoms, or have been a close contact, the best thing to do is test again. Doing multiple tests will increase your chances of getting a correct result.
The incubation period for Omicron is about two to four days, so doing a test on the day of contact may result in a negative test despite infection occurring.
Martiniuk urges everyone to remember to report their positive RATs online or by phone. This helps keep track of the case numbers, but more importantly connects you to health services.
Lydeamore’s advice was straightforward. “If you have a negative RAT and have symptoms, and you truly think that it’s a false negative, then my recommendation would be to go and get a PCR.”
I have isolated for seven days, what should I do now?
No test is required to leave isolation in all states except for SA. However, a mask should be worn around other people and high-risk places such as aged care facilities and hospitals should be avoided for at least the next three days.
Regardless where you are, if you still have symptoms after seven days, it is best to remain in isolation until at least 24 hours after your symptoms have resolved.
Martiniuk recommends telling people who you spent time with from the two days before you started having symptoms or the two days before you tested positive (whichever came first) that you have Covid.
After your Covid infection and your seven-day isolation you don’t need to test or self-isolate for the following 12 weeks. If you are due for a vaccine, the recommendation is to wait about four to six weeks to give your body a chance to recover.
• This article was amended on 12 April 2022. Western Australia is not one of the states that requires a test in order to leave isolation, as an earlier version said.
