Covid testing: Which is the most reliable Covid test? What’s the difference between them?

Covid-19: Cignpost Diagnostics explain different test types

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As lockdown begins to ease in the UK, widespread testing will be key to preventing coronavirus spiralling out of control again, alongside the rollout of the vaccine programme. Testing is widely available for people with symptoms, but with a large number of Covid carriers asymptomatic, the government has said it plans to offer millions of home testing kits to help society get back up and running.

So what are the different tests and which is most reliable?

Lateral flow

Lateral flow, or rapid antigen, tests are becoming more widely available, with many local councils running testing centres for people without symptoms, often in town halls and community centres.

A lateral flow test gives a result in about 15 to 30 minutes.

With these tests, you still have to swab the nose and throat, but the swab is dipped in a fluid which is then dropped onto a plastic device, a little bit like a pregnancy test.

One line will appear on a paper strip showing the test has worked, a second line will show if you have the virus.

These tests, while thought to spot the majority of the most infectious cases, are less sensitive and can miss cases of the virus, as well as providing false positives.

A major review published at the end of March concluded that lateral flow testing was too inaccurate to be used in mass screening, for example to allow people to go back to work.

The Cochrane review of 64 studies found that asymptomatic testing only picked up around 50 percent of cases, and picked up far more false than real positives when infection rates were low in the community.

And SAGE, the government’s scientific advisory group, has warned that with mass testing using lateral flow tests, false positives and false negatives could have “critical implications” for effectiveness,


PCR (Polymerase Chain Reaction) is currently the most common form of testing in the UK and, at 99 percent accuracy, is widely accepted to be the most reliable test.

In most cases, a nose and throat swab is taken and sent to a lab for processing, with results usually ready between 24 and 48 hours later.

There are also rapid turnaround versions of these tests, mostly available in hospitals.

A PCR test can also detect if you’re infected before you become infectious, making it a key tool in managing the spread of Covid.

Denis Kinane, Chief Medical Officer at Cignpost Diagnostics, told “[We] recommend the gold standard PCR test for anyone wanting to go back to work or travel abroad safely.

“It is the only test that gives you almost 100 percent certainty about whether you have the Covid virus or not.”


Mr Kinane explained that LAMP (loop-mediated isothermal amplification) tests are similar in process to PCR testing.

These are the least common type of tests, and, like lateral flow tests, LAMP tests can only detect a high load of COVID-19 virus, so they can miss people in the early stages of infection.

They require a swab from the nose and throat and give results within 90 minutes.

If you need to book a Covid test, go online or call 119.

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