Lateral flow vs PCR tests: what is the difference?

We’re all used to hearing about lateral flow COVID-19 tests and PCR COVID-19 tests by now, but it can still be confusing to know the difference. These tests are used in different circumstances, so it’s important to know which is which.

With travel testing for Covid still important and with online searches for terms like ‘travel test UK’ and ‘UK Covid testing’ still very popular, understanding which test you may or may not need remains important.

Distinguishing these two types of tests becomes even more important when you’re considering travelling abroad, as confusing the two and getting the wrong type of test could mean a barrier to entry.

What is a lateral flow test?

Lateral flow tests are sometimes known as rapid COVID-19 tests due to the quick results that they provide. The lateral flow device works by detecting if a COVID-19 antigen – something produced by a person who is infected with COVID-19 – is present in the sample provided.

The test itself involves inserting a swab into the nose, throat, or both, which is then processed on-site. This swab is inserted into a tube of liquid that extracts the COVID-19 virus if it is present. A few drops are then added to the strip in the lateral flow device, which will show the result in 30 minutes. Two lines mean a positive result, one line next to the C mark means a negative result, and one line next to the T mark means an invalid result.

When should I use a lateral flow test?

Usually, lateral flow tests are used when someone does not have symptoms of COVID-19.

Currently, it is only advised to get a COVID-19 lateral flow test in England if:

• You are a close contact of someone who has tested positive for COVID-19
• You visit someone who is at a higher risk of becoming seriously ill with COVID-19
• You work, volunteer, or visit somewhere that is high risk
• You are eligible for new COVID-19 treatments
• You want to find out if you can leave isolation after five full days

Where can I get lateral flow tests from?

Lateral flow tests in England are no longer available free of charge from the numerous locations from which it was previously possible to acquire them, such as pharmacies and schools. Lateral flow tests in England are now only available for free for specific people (such as some healthcare workers) and for others, they need to be purchased for a fee from a pharmacy or online.

What is a PCR test?

A PCR (polymerase chain reaction) test is a more sensitive test, being able to pick up even small traces of the COVID-19 virus. Depending on where you are travelling, you may need to order and administer a PCR test kit for travel, before you board the plane to your destination. For example, if you are currently looking to travel to the likes of Israel or the USA, you will need to have carried out a test before boarding your flight.

Similar to the rapid lateral flow test, during the PCR test a swab will be inserted into the nose, mouth, or both. However, this sample will then be sent off to a laboratory for testing, rather than using a lateral flow device.

When should I use a PCR test?

PCR tests are usually used by people who have symptoms of COVID-19, or those who need to take one in order to be able to travel abroad.

If you’re taking a PCR test because you have symptoms of COVID-19, you should take the test as soon as possible after your symptoms start. PCR tests need to be completed within the first eight days of having symptoms of COVID-19.