COVID TESTS – WHAT’S THE DIFFERENCE BETWEEN THEM ALL?

Since March 2020, the world has had to learn a whole new language thanks to the SARS CoV 2 virus, and Covid-19, the infection it causes. Antigens, lateral flows, aerosol transmission, social distancing, vaccine passports, vaccine hesitancy, long Covid, PCRs…the list is endless.

But, even now, there is still a degree of confusion around Covid testing, especially as travel testing or event testing regulations change so often.  So, if you need a reminder, here’s a quick rundown of the tests and what they are used for…

But, even now, there is still a degree of confusion around Covid testing, especially as travel testing or event testing regulations change so often.  So, if you need a reminder, here’s a quick rundown of the tests and what they are used for…

What is a rapid antigen test?

Antigens are antibody generators…they are particles that stimulate an immune or antibody response to help us fight off infection. The Covid rapid antigen test detects proteins on the surface of the virus, from a sample, usually a swab from nose or throat. It’s rapid as it doesn’t need a lab – instead your swab sample is analysed in a small test cartridge like a pregnancy test, using the lateral flow technique. That’s why these tests are also called lateral flow tests. What is a rapid antigen test used for? It’s simply to detect whether you have Covid infection at the time of testing.

What is a lateral flow test?

When it comes to Covid tests, a lateral flow test and a rapid antigen test are used interchangeably. Lateral flow just describes the way the sample and fluid flow along the testing channel until they reach the point where any antigen (virus particles) are detected…or not!

How accurate are rapid antigen / lateral flow tests?

As long as the test itself has been CE approved, these tests are very accurate…but only if done properly. Studies have shown that they may be accurate in only 50% or so, if done without proper medical supervision. But, if done well, in people with active and potentially spreadable virus, they are accurate in over 95%.

If your properly conducted test is positive, you can be almost certain you have Covid. False positive rapid antigen covid tests are rare. If your test is negative, there is still a small chance you could have Covid…maybe you didn’t swab well enough or maybe your Covid is just starting to develop and not yet detectable. Repeat the test if you have doubt.

Will I test positive after Covid vaccine?

No, the vaccine will not cause you to have a positive lateral flow test. If you have a positive rapid antigen lateral flow test after vaccination, you have Covid, and should get a PCR test to allow the result to be recorded and to test for variants.

What is a Covid-19 PCR test?

A Covid-19 PCR test is a lab-based test for current infection, that also requires a swab sample – often requesting both nose and throat (nasopharyngeal). As it needs lab analysis it takes a lot longer – a few hours to a few days. It picks up genetic material from the virus and may be more sensitive than an antigen test. Sometimes that’s a good thing – it can detect virus in the early stages.

But it can also stay positive for 90 days after you have had Covid, long after your infection has passed, when you are no longer infectious to others. That’s a problem if you are barred from travel or forced to quarantine unnecessarily as a result.

Like the lateral flow test, a PCR test will not show as positive after vaccination – only with Covid.

What is a LAMP test?

Less commonly used than a lateral flow or PCR test, LAMP tests are another way of testing for current infection. They can be quicker than PCR tests but can’t be done at home so are less convenient than lateral flow tests.

What is a Covid antibody test?

Unlike the rapid / lateral flow antigen test, the PCR test or LAMP test, which aim to identify current infection, the Covid antibody test can show evidence of past infection or response to vaccination.

When you have an infection, your body’s immune system produces antibodies.

If your immune system is working well, you should see levels of various antibodies rising at different intervals after infection, as these defences kick in.

What does a positive Covid antibody test mean?

If you have a positive Covid antibody test, especially if it is a specific neutralising antibody test, it suggests you are less likely to catch Covid or to have a severe attack if you do. Vaccines have reportedly prevented over 46,000 hospitalisations and saved over 30,000 lives by stimulating antibodies to the virus.

A positive test provides reassurance that a severe infection is unlikely – though shouldn’t mean you throw caution to the wind, of course. If you have a negative antibody test, it doesn’t necessarily mean that you have no immunity to Covid as the test doesn’t identify all the defences. But it may mean you take even more care.

How long do Covid antibodies last?

Whether after infection or vaccination, antibody levels seem to drop off after a few weeks or months. This rate varies from person to person. How much that matters is still unclear, as the body has a second line of defence, meaning it may be able to respond more quickly to an infection they have seen before, hopefully nipping it in the bud. We’re not sure how well that system works yet – so we are looking at how antibody levels change with time and whether vaccine boosters are needed.

If you want to know more about Covid antibody tests, have a look at this article.

Where can I book a Covid antigen or Covid antibody test?

If you need a Covid antigen test for travel or other needs or you’d like to find out about your own antibody status after infection or vaccination, you can use one of our self-tests, at home. If you’d like online support or certification from our specialist nurse, please add a supervision appointment to your basket too.