There’s a lot of misinformation out there regarding rapid antigen lateral flow tests…promoting, instead, the more expensive PCR tests that need a lab and can take a day or two for results. PCRs are regarded as the gold standard but are they really the best test for the job?
PCR tests are certainly more sensitive, picking up tiny traces of viral material. But a positive PCR test doesn’t necessarily mean that someone is infectious – they can stay positive for around 90 days, long after the infection (that you may not even know you had) has gone! That means unnecessary quarantine, inability to go to work and disruption for you and any close contacts. And, lots of PCR tests are being done at home, without supervision, so we really have no idea who is actually taking the test and when! By the time the result arrives, it is out of date anyway.
In direct comparison, rapid antigen lateral flow tests (which are cheaper, easier and provide results in minutes) are reported as being less accurate. But that's not a fair comparison, because rapid antigen lateral flow tests are developed to look for high viral load….when people are most likely to be infectious. Not to pick up the residual traces when the infection has passed!
PCR tests still have a role – they can help detect new variants and may pick up Covid in the very early stages when viral load is low, which can be useful in certain specific situations.
Of course, the result is only as good as the test used and the sample taken. So, it’s important to use a test with proven accuracy and ensure that any sample is supervised by a healthcare professional, as this has been shown to give the best results of around 95% accuracy in the case of rapid antigen testing. That’s why these tests aren’t currently licensed for home use. That may change – but so, then, will accuracy…..unless you use a service like Breathe Assured where your home-delivered rapid antigen test is supervised online by a healthcare professional to ensure good technique, validate the result at 15 minutes and provide an instant certificate for travel, work or whatever you need.
They don’t provide a cast iron guarantee that you’re negative (no test does) and they are certainly not an excuse to stop using standard safety measures, but they help to detect people who have Covid without knowing it (around 40%) and so can spread it without knowing. That's why we use them all the time in the NHS and why the government is promoting their use elsewhere too.
But as we start to get back to work, travel and leisure, and understand that living with Covid is likely to be long-term, regular rapid antigen testing will help to reduce spread and add reassurance.
Read more of the science here.