Covid lateral flow tests: How accurate are they – can you get a false positive?

Lateral flow tests are a vital tool in helping us track the spread of Covid, but some have voiced concerns at their level of accuracy, and it has been found the tests may not always show the correct result

We need lateral flow tests to help people keep on top of the coronavirus
We need lateral flow tests to help people keep on top of the coronavirus

Lateral flow tests are hugely important in our effort to tackle the coronavirus pandemic.

The free testing kits can help tell us if we have the Covid-19 virus, even without having symptoms.

The advantage of lateral flow kits is that they allow you to get an answer in just 15-30 minutes.

This has been a great way for people to check they aren’t carrying the virus when they see family and friends.

However, they are not as accurate as a polymerase chain reaction test, known as a PCR, and this has led some people to worry that lateral flow tests can be inaccurate. So how well do they work?

How accurate are lateral flow tests?

The Flowflex lateral flow test


Sophs Forte / SWNS)

The odds of a lateral flow test giving an incorrect positive test result are relatively low, but a ‘false negative’ is possible.

According to research by medical database the Cochrane Library, lateral flow tests only detect 72% of cases where people have symptoms and 58% where people don’t. It can mean that those with a false negative have their case undetected and continue to spread the virus.

Though considered to be one of the main forms of defences against the pandemic we have, some experts have raised concerns over how effective lateral flow tests are with detecting the new Omicron variant.

People showing the ‘milder’ coronavirus symptoms connected to the rapidly spreading strain have been told to get a PCR test.

Dr Angelique Coetzee, chair of the South African Medical Association, said she was aware of a problem occurring where some lateral flow tests would show negative results for Omicron, but a PCR would detect a positive result.

“We do have patients that waited a week and still have a headache and then they do PCR and it’s positive,” she said.

Is my lateral flow test a false positive?

False positives are extremely unlikely to occur


Getty Images/iStockphoto)

While false negatives have been shown to be common, false positives are pretty unlikely.

The UK Health Security Agency (UKHSA), an executive agency sponsored by the Department of Health and Social Care, said that there is a less than one in 1000 chance of a positive test being wrong.

“The LFDs that we are using have a high specificity, that means the number of false positives are extremely low – less than 1 in 1000 tests conducted from our studies,” they said.

“However, as the prevalence of Covid-19 reduces to low levels in the population, the chance of a false positive result increases – though still remains unlikely.”

So, if you get the dreaded two red lines on your lateral flow test, you’re almost certainly positive for Covid-19.

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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