Is a rapid antigen test sufficient or do I have to line up for a PCR?
Christmas is approaching and I pray that on the 12th day my true love does not give me COVID.
None of us want to accidentally infect our loved ones this holiday season, but as NSW broke a new daily record today with 3,763 cases, queues at test sites and wait times for results nationwide are bonkers.
We have access to PCR tests (polymerase chain reaction tests) as well as rapid antigen tests (also called lateral flow tests) to detect SARS-CoV-2, the virus that causes COVID.
So would a rapid antigen test Will it be enough to keep Chrissy COVID-free? In this critical time before Christmas, there are obvious pros and cons for both.
PCR test – Advantages
PCR tests are used in many scientific applications, but our COVID testers use them to look for SARS-CoV-2 genetic material, which is then copied and copied billions of times to the point where it can be detected. They are up to 99% accurate because they are able to detect the virus even from the smallest amount of it on your sample.
PCR test – Disadvantages
The biggest disadvantage of the PCR test is that it is time consuming. Since laboratories use machines that process multiple samples at once, each batch takes approximately six hours from when it is placed on the plates to when the result is evident.
Samples are also not tested on site. Depending on the site you are visiting, the laboratories responsible for the tests will perform a few collections per day. So even if you arrive at, say, noon, you may have missed the morning pickup and your sample won’t be taken until the site closes at 5pm.
Right now, everyone has the same idea of getting tested before the holidays and Christmas lunches. For some it’s an interstate travel requirement, for others they get pinged left, right and center as the Omicron outbreaks in NSW, ACT, QLD, and SA grow.
Some testing sites in Melbourne hit maximum capacity before they even open for the day, while others in Sydney don’t return results for five days.
There have been countless anecdotes of people queuing up to eight o’clock, and even members of our own editorial team waited up to four hours for testing this week.
Rapid Antigenic Tests – Advantages
Rapid tests are incredibly fast and easy to use.
These tests look for viral proteins rather than genetic material.
You give your nostrils a little, soft swab, you dip your tampon in a solution, that solution drip onto the test, which works like a pregnancy test.
The solution allows viral proteins to bind to antibodies which fluoresce to indicate the presence of the proteins.
You also don’t have to deal with massive test lines or waiting times for results. They take about 15 minutes to give a result, and can be done at home.
Rapid Antigenic Tests – Disadvantages
Rapid tests are much less accurate than PCR tests because no amplification process is involved to make copies of the small amount of virus you might have.
Rapid tests are only about 77% as accurate as PCR tests, according to an Australian study, and will work best if someone has a high viral load, that is, if you have been infected for several days.
If you are already having symptoms, the rapid test will be much more accurate at identifying the infection because you have a lot of lurgia in your fluids.
This means that false positives are very unlikely on rapid tests if used correctly, but false negatives are quite common for asymptomatic people who have just contracted the virus.
Rapid tests are also in high demand right now and are being sold in supermarkets and drugstores across the country because until, like PCRs, they are not free. So good luck putting on your mittens.
So when should I use which one?
You should take a PCR test if there is a known reason why you might have COVID. This includes, any symptoms, being in close contact or visiting an exposure site.
Rapid tests are considered a screening tool for prevention. It is best to consider them as a safety measure when there is no reason to suspect an infection.
They can be used before visiting a sensitive environment like a hospital or visiting your grandparents in a retirement home, before a big social event, or before going to work if you interact with others.
Which one should I choose before Christmas?
A PCR test is the only way to really sleep soundly on this before Christmas, especially if there will be vulnerable people at the dinner table, or if you’ve been a social butterfly that’s been hitting the club a lot lately.
But if not, rapid antigenic tests for everyone present could also provide you with relief. Plus if you have your gathering outside, you further reduce the risk of infection.
Good luck to all of you and be careful.
Image: Getty Images / Cameron Spencer