COVID rapid test: How to get the most accurate result

With Canadians throughout the nation nonetheless confronted with restricted entry to polymerase chain response (PCR) testing, speedy antigen exams stay a fast and straightforward method to inform whether or not or not somebody has COVID-19.

However a current examine carried out in the USA revealed that these speedy exams could also be much less delicate to newer variants of the virus, and subsequently much less efficient at detecting their presence. This will go away some questioning simply how correct speedy antigen exams really are, particularly as Canadians navigate a sixth wave pushed by the Omicron variant.

“The exams do work, they’re nonetheless detecting COVID,” Dr. Christopher Labos, a Montreal-based heart specialist and epidemiologist, informed CTVNews.ca in a cellphone interview on Might 18. “We simply have to know their limitations.

“What we’re seeing with the Omicron variant and different variants is that false negatives are a problem.”

The opportunity of receiving a destructive outcome whereas being contaminated with COVID-19 is the most important limitation of utilizing these exams, Labos mentioned. The reason for a false destructive result’s unlikely to stem from points with figuring out the most recent COVID-19 variant of concern attributable to new mutations, mentioned Dr. Lisa Barrett, an infectious illness specialist and professor at Dalhousie College in RisePEI. As a substitute, it might need extra to do with how the check is being carried out, and the place an individual is of their course of an infection.

“It isn’t a check detection downside,” Barrett informed CTVNews.ca on Might 18 in a cellphone interview. “It might be that the virus itself hangs out in numerous components of your respiratory tract at totally different occasions within the an infection.”

In the beginning of an an infection, the Omicron variant tends to be most current within the throat, Barrett mentioned. Because the an infection progresses, it begins to pay attention within the nasal space and in a while, may even transfer down additional into the respiratory tract, which could then produce a destructive outcome, she mentioned. That is why specialists, together with Barrett, recommend swabbing extra than simply the nostril when utilizing a speedy antigen check, regardless of producer directions.

“We advise utilizing a swab that reaches the again of the throat, swab either side – it’s best to get just a little little bit of a gag – after which do either side of the nostril,” she mentioned. “That is your greatest pattern to get the most effective sensitivity, even for early and low an infection.”

Notably for these displaying symptoms of COVID-19, a single destructive check might not fully rule out an infection, particularly since Omicron continues to flow into at excessive ranges in numerous components of the nation, Barrett mentioned. However it could point out that the probabilities of passing the virus on to others at that time are low. In the end, the purpose of speedy exams just isn’t essentially to rule out an infection, however decide the chance of spreading COVID-19 to different individuals, mentioned Barrett.

“Optimistic exams are actually essential and nonetheless appear to be linked with increased infectiousness to different individuals, which is the way in which we’re attempting to make use of the instrument,” she mentioned. “The instrument was by no means meant to rule out an infection for somebody to allow them to go and do one thing that could be dangerous if they have signs – it is to rule in an infection.”

WHEN SHOULD YOU TAKE A RAPID TEST?

If somebody is displaying signs of COVID-19 however receives a destructive outcome utilizing a speedy check, they need to check themselves once more at the least a few times extra, Labos mentioned, ready about 24 to 48 hours between every check.

“The purpose is to check repeatedly,” Labos mentioned. “There are fairly numerous individuals who examined destructive on their first check, solely to check constructive on their second or third check.”

Earlier this yr, Ontario’s COVID-19 Science Advisory Desk published data indicating that the sensitivity of speedy antigen exams in the direction of the Omicron variant various relying on how far alongside somebody was of their an infection. Outcomes confirmed that check sensitivity was slightly below 20 per cent when taken two days after an preliminary constructive PCR check. By day three, sensitivity shot as much as over 80 per cent.

Consequently, Labos advises individuals to attend a couple of days after the onset of signs earlier than taking a speedy antigen check.

“In case your signs began in the present day, you wish to wait [for results from] a repeat check on day three, that is the one which’s going to provide the greatest bang in your buck by way of diagnostic accuracy.”

For many who will not be symptomatic, however wish to take a speedy check earlier than getting along with family and friends, for instance, Barrett recommends performing the check instantly earlier than assembly with others.

“If you are going to check in that state of affairs, with out signs, do it proper earlier than you stroll right into a gathering … and [swab] your throat and nostril,” she mentioned. “Don’t do it 12 hours earlier than as a result of [the virus] can change by way of its stage.”

WHAT EXACTLY DO RAPID TESTS MEASURE?

Fast antigen exams are usually designed to focus on the N-gene product, or the nucleocapsid protein, of SARS-CoV-2, Barrett defined. That is totally different from detecting the virus’ genetic materials or antibody ranges, which generally rise when somebody has both been contaminated with the virus, or acquired a COVID-19 vaccine, Labos mentioned.

“You’ll solely have that protein in case you are actively contaminated with COVID-19, the vaccine received’t impression that,” he mentioned. “Even if you happen to obtained vaccinated, you’ll nonetheless check destructive if you don’t actively have COVID.”

That is totally different from how PCR exams are carried out, as they detect components of the S-gene of SARS-CoV-2, in any other case generally known as the spike protein. PCR exams are thought-about extra correct in detecting COVID-19 than speedy antigen exams, Labos mentioned, however that doesn’t imply it’s essential to take one with a purpose to verify outcomes from a speedy antigen check, particularly if somebody is symptomatic.

“If it appears like a duck and quacks like a duck, it is in all probability a duck,” he mentioned.

Given the restricted eligibility to PCR testing in numerous components of the nation, speedy exams proceed to play a helpful position in detecting COVID-19, significantly as a result of they’re self-administered, can conveniently be carried out at residence and produce outcomes inside about 20 minutes, Barrett mentioned.

With the advice that folks ought to be taking a number of COVID-19 exams to find out if their signs are brought on by COVID-19, Labos mentioned it’s useful to order one speedy check package for every individual dwelling at residence. Every package usually comes with 5 exams.

“If you consider the sensible realities of getting to do a number of exams if you happen to get sick … it’s best to just remember to have sufficient speedy check kits to ensure that each individual in your home can do two, three or 4 speedy exams if the necessity arises.”

WHAT SHOULD YOU DO IF YOU TEST POSITIVE?

Lastly, if somebody have been to check constructive utilizing a speedy antigen check, step one ought to be to self-isolate, Barrett mentioned. Provinces have various necessities for self-isolation after publicity to COVID-19. In Ontario, for instance, residents are anticipated to quarantine for at the least 5 or 10 days, relying on their vaccination standing, and should proceed isolating if signs haven’t improved or in the event that they proceed to have a fever. In Nova Scotia, nonetheless, the requirement is to self-isolate for seven days from the onset of signs, no matter vaccination standing.

To be able to scale back the probabilities of infecting others, Barrett recommends that those that are sick keep residence for at the least seven days and wait till their signs have resolved earlier than ending their self-isolation interval. It’s additionally a good suggestion to take a speedy check in the direction of the tip of the isolation interval to find out whether or not or not an individual continues to be infectious.

“That’s most helpful to exhibit that you simply’re nonetheless constructive and should wish to keep residence a day or two longer, significantly if you happen to work with weak individuals … or you have got individuals in your fast circle which are weak.”

WHERE CAN YOU GET RAPID TESTS?

Alberta: Rapid test kits can be found at certain pharmacies throughout the province, and a few Alberta Well being Companies clinics.

British Columbia: Fast exams are available for free at neighborhood pharmacies.

Manitoba: Residents can discover speedy exams at provincial testing locations in addition to pharmacies, grocery stores, and certain libraries.

New Brunswick: Fast exams are accessible to residents with COVID-19 symptoms by the province’s online portal.

Newfoundland and Labrador: Fast exams are being administered by testing packages held at schools, health-care centres and different services.

Northwest Territories: Residents can entry speedy exams at no cost at Northern Shops throughout the territory, in addition to the Yellowknife Fieldhouse and City Hall.

Nova Scotia: Fast exams can be found for choose up at local MLA offices throughout enterprise hours. They’re additionally obtainable at Access Nova Scotia places, public libraries, family resource centres, and choose meals banks and pop-up testing websites.

Nunavut: Fast exams will be discovered at Northern and NorthMart Stores.

Ontario: Fast exams can be found at no cost at choose pharmacies, grocery stores and thru some neighborhood companions.

Prince Edward Island: Residents can entry speedy exams at Access P.E.I. offices. Checks are additionally being provided to these enrolled in schools and daycare facilities, in addition to long-term and neighborhood care.

Quebec: Fast exams can be found at most pharmacies, and to these enrolled in schools and child-care facilities.

Saskatchewan: Fast exams can be found to the general public free of charge at sure grocery shops, gasoline stations, libraries, metropolis workplaces, and different public distribution centres.

Yukon: Residents can entry speedy exams at select stores and pharmacies in Whitehorse, and community administration buildings.