How best to use a COVID-19 rapid antigen test

As COVID-19 cases surge in Ottawa, many people are relying on rapid antigen tests to ensure they are virus free, and while false negative test results are possible, proper administration will provide much better odds for an accurate result.

Rapid antigen test kits are free and readily available at most pharmacies and grocery stores across Ontario. 

Many people who pick up the tests have similar reasons for taking it - such as children in school, visiting aging family members, and ensuring they are COVID-free before travel. The test only takes about 15 minutes, and it is seemingly simple to get results.

However, the reality is, it’s not all that perfect, most rapid tests detect the virus about 70 per cent of the time. 

"We’re giving out lots of the kits for people to test at home," says pharmacist Jordan Clark, owner of Westboro Shoppers Drug Mart. "You want to make sure you’re taking the time to set up the test correctly and most importantly that you are swabbing correctly whether you’re administering the test on yourself, a loved one or especially a child."

Clark has likely administered thousands of tests throughout the pandemic. He says pre-Omicron, rapid tests were being used predominantly in the nostrils. But some of the newer strains live in the throat and tonsils.

In order to yield the best test, lay the test kit out, read the instruction and do not rush. Clark says start in the mouth and swab the inside of both cheeks for five seconds each, followed by another five-second swab at the back of the throat and tonsils - and spin the swab around.

Move on to both nostrils, five seconds each, and around the perimeter is not enough. So how deep?

"You want to go as deep as you can until you feel some resistance and then a little bit of a push more so it should be slightly uncomfortable," says Clark.

Place the swab in the test tube with the solution and squish the side. Leave it there for the recommended amount of time, the liquid breaks down the particles to extract the COVID antigens. 

Add the recommended number of drops to the test strip and wait the full 15 minutes. Depending on your virus load, the result could be faint. 

If the test is positive, it’s highly unlikely to be incorrect.

"The other thing that’s important is frequency of testing," Clark says. "So not just a single test but that we are testing three, four, five times a week, that’s a better chance that you are going to capture a positive case if you are positive."

Why are some people COVID-negative when exhibiting symptoms?

Infection control epidemiologist Colin Furness says it has to do with an individual's vaccination status.

"If you’re vaccinated, you start to get symptoms right away after you have been exposed very soon because your body mounts a response right away because your body recognizes the virus right away,” says Furness. "So you’re not very infectious yet and you are showing symptoms because your vaccinated your body fights it off more quickly and you are done with your symptoms but the virus is still shedding and you end up being contagious after your symptoms not during."

Furness adds that unvaccinated individuals will likely show a positive rapid test result at the onset of symptoms and it is important to note that if a test comes back positive, unlike a PCR or molecular test, you are likely to be contagious.

“The advice we’ve had from public health that says after five days after symptoms you can go back to work, that is actually designed to infect people. That doesn’t protect people, that’s a terrible idea,” he says. "If you are vaccinated, you really want ten days from when the infection showed up to when you start exhaling in front of other people because of that infectious period after symptoms are done."

If you feel unwell, are sick or are testing positive, most medical experts will say the best result is to simply stay home.