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Lateral flow test

Written by Caidr's team of doctors and pharmacists based in UK | Updated: 04.04.2022 | 3 min read
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A lateral flow test looks for certain markers (proteins and hormones) on a sample of fluid, to give a positive or negative result. There are many different types of lateral flow tests - you may be familiar with a home pregnancy test or the quick COVID-19 test, both of which are rapid lateral flow tests.

The COVID-19 lateral flow test used to be available for free and we were encouraged to take regular tests to attend work or school, or take a test before meeting anyone vulnerable, or going to events or crowded places. This was designed to catch those without symptoms and prevent spread.

Is it still free?

Rules have changed from April 2022, and tests are no longer free in England, except for certain vulnerable people, such as the over-75s or those over 12 who have weakened immune systems. Frontline healthcare workers or social workers can also get free tests.

Scotland, Northern Ireland and Wales are following suit by lifting all legal restrictions, including access to free lateral flow tests, but they follow slightly different timelines.

Once tests are no longer free, you may still wish for the reassurance of negative lateral flow tests, especially if you have vulnerable people in your life, so they are available to buy from pharmacies and certain retailers.

Lateral flow tests were also available for free to end self-isolation required by law if you were positive for COVID-19, but rules have changed for this, too, in England.

How does it work?

A lateral flow test for COVID-19 has been developed which detects a protein (known as an antigen) that the body produces while fighting a current COVID-19 infection. The test cannot tell you if you have had COVID-19 in the past. Taking 20 to 30 minutes to get a result, a lateral flow test tends to be much quicker than a COVID-19 PCR test, where the samples must be sent off to a laboratory.

At the start of the COVID pandemic, lateral flow tests were thought to be significantly less accurate than PCR tests, but studies have found that when used correctly, they are around 80% effective at detecting any active COVID-19 infection.

Around a quarter of people who have COVID-19 don’t get any symptoms, so many people felt reassured with regular testing or if visiting elderly or vulnerable relatives or meeting lots of people.

What happens in the test?

In the UK the testing is done by using a clean sterile swab (a thin plastic stick with a soft end, like a cotton bud) to collect secretions from the inside of your nose and at the back of your throat, near your tonsil area. You need to twirl the swab around for 5 seconds in each area. This can be uncomfortable, make your eyes water or make you gag.

The swab then goes into a pot containing some fluid where you will twist and press the swab against the side to release the secretions into the fluid. If you are doing the test for yourself, you will then put a few drops of this fluid onto the lateral flow device. After waiting a specified number of minutes, you are then able to read the results from your device.

Devices differ, but usually, two lines means a positive result, one line means a negative result (or occasionally an invalid test). Instructions may vary slightly with different testing kits, so remember to always read the label and check the expiry date.

Am I fit for work if I have a positive lateral flow test?

The rules in England have changed, so it is not a legal requirement to self-isolate if you know or suspect you have COVID-19, but you are advised to stay home for at least 5 days. The UK government now leaves the responsibility with you to reduce the spread of infection by avoiding others and staying home. Your employer may have clear rules, but this relies on you to declare you have symptoms or have had a positive test.

Your co-workers may not thank you for turning up, and neither will friends and family, but we are all learning to live with the virus now, rather than to completely avoid it, so our attitudes to risk are changing with time.

*Information correct on 4 April, 2022

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