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COVID-19

PCR or Lateral Flow Which test is the right test?

The difference between a PCR test and a Lateral Flow Test

Please read this information as there still seems to be a lot of confusion between the two types of testing with children showing symptoms or wider symptoms being given a home Lateral Flow Test rather than the correct PCR test at a test centre.

A PCR test is to be used for unwell adults/children (this is for Covid symptoms or any of the wider symptoms).

 

LATERAL FLOW TESTS

Lateral Flow tests MUST not be used for adults/children who are unwell.
These are the rapid tests that are used in the community. They are convenient because they can give a result within 30 minutes and do not need a laboratory.

They detect proteins from the virus, not RNA. They use a swab of the nose and/or throat and are carried out on a small flat plastic device like a pregnancy test.

These tests are very different from PCR. They are NOT SUITABLE for diagnosing individual patients who suspect they may be infected because they have symptoms.

People with symptoms need a PCR test. Lateral flow tests are intended for picking up additional infected cases who would otherwise be missed because they don’t have any symptoms.

 

WHEN SHOULD I HAVE A LATERAL FLOW TEST?
You should only have this test if you don’t have any symptoms.

 

PCR TESTS
PCR tests detect the virus’ RNA. These tests are normally carried out in a laboratory using a swab of the nose and/or throat.

PCR tests can detect very tiny amounts of RNA, meaning they are extremely sensitive. They are the best test for current infection.

Patients with COVID-19 usually start to become positive by PCR testing a day or two before symptoms start and will continue to test positive by PCR afterwards for some time. Repeat PCR once a diagnosis has been made is not necessary.

The period the patient must isolate for is defined by time from the start of symptoms or, if there are no symptoms, from the first positive test. Current UK policy is that patients must self-isolate for ten days after this time.

 

WHEN SHOULD I HAVE A PCR TEST?
If you currently have symptoms that may indicate COVID-19, this is the test you should have to diagnose the infection.
If a lateral flow test is positive. The purpose of the PCR test is to confirm the diagnosis, since it is a more accurate test than the lateral flow test.

Information on wider symptoms testing from Public Health

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