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Who should use them and how to interpret your results.

First published:
23 February 2021
Last updated:

Overview

Lateral flow test (LFTs) are used to identify people with COVID-19.

Each positive case identified can help prevent many more infections.

LFTs are easy to use and give results in 30 minutes.

How lateral flow testing works

Lateral flow is an established technology, adapted to detect proteins that are present when a person has COVID-19. The best-known example of a lateral flow test is the home pregnancy test kit.

The test kit is a hand-held device with an absorbent pad at one end and a reading window at the other. Inside the device is a strip of test paper that changes colour if COVID-19 proteins are present.

How to take the COVID-19 lateral flow test

Watch a short video demonstration of how to take the test.

Video: how to self-test (British Sign Language version)

Live video assistance for people with sight loss is available now. Call 119 to access this service.

There are different types of lateral flow tests. Some use samples from just your nose. Others use samples from your throat and nose. All are proven to be highly effective at detecting people who are infectious with COVID-19

Use the swab to take a sample from the back of your throat and from your nose, or just from your nose, depending on the type of test you are using. Refer to the instructions in the pack.

Once you have taken the sample, dip the swab into an extraction solution and then onto the lateral flow test’s paper pad.

You will see the result from between 15 and 30 minutes after you have applied the sample, depending on which type of test you have used. There is no need to send the sample to a lab.

How to interpret the results

Image
Image showing the results a lateral flow test might show

 

Negative result: 1 line next to C

Positive result: 2 lines, 1 line next to C and 1 line next to T

Even faint lines mean that your test is positive for COVID-19.

You or your test provider must report this test result (positive or negative) to the NHS.

Void:  No lines or 1 line next to T. This means the test is invalid. Re-take the test with a fresh test kit.

A negative result does not guarantee that you do not have coronavirus. The test might not detect the virus if you were recently infected or are in the incubation at the time of the test.

You must continue to follow coronavirus rules, including:

  • regular hand washing
  • wearing face coverings where required

What to do if you have a positive lateral flow test result

If you get a positive lateral flow test result, self-isolate immediately and follow the self-isolation guidance.

Report your lateral flow test results

Once you have done your lateral flow test, you need to report the results. You need to report all results within 24 hours, whether positive, negative or void. 

Report your results on GOV.UK or by calling 119. Calls are welcomed in Welsh.

This helps our understanding of current COVID-19 rates. It means new outbreaks are identified. It also helps us to understand how tests are used.

Who can be tested?

Lateral flow testing is currently being offered to people who have symptoms. They are also being used for regular testing of NHS and social care staff and special schools. 

How accurate are lateral flow tests?

Lateral flow tests are validated technology. Extensive clinical evaluation from Public Health England and the University of Oxford show Lateral Flow Tests (LFTs) are specific and sensitive enough to be deployed for mass testing, including for asymptomatic people.

How sensitive are the tests?

The lateral flow tests cannot detect very low levels of coronavirus in a sample. This means if you have only recently been infected, are in the incubation period, or if you have mostly recovered, the test may not give a positive result

Test sensitivity for lateral flow tests is also dependent on the person who does the test. Training and regular use helps to mitigate this as people become more proficient in using lateral flow tests.