The Difference Between PCR Tests and Antibody (IgG/IgM) Tests

Last Reviewed: 3rd May 2020

PCR Tests

This tests for presence of the virus on swabs. It does not test blood.

A PCR test looks for the presence of the RNA of the virus itself. This means that it will pick up the presence of the actual virus in the nose and throat. It is 100% accurate and will be able to confirm whether anyone with symptoms has the virus. It will also pick up whether the virus is present for people who have been exposed but are not showing any symptoms as yet. So long as there are viruses present on the swab the laboratory receives it will be reported "virus detected"

NB: This test only picks up whether there is virus on the swab that is delivered to the laboratory. If you have recovered and the virus has been cleared from the body, or the swab is not taken carefully and thoroughly as per the instructions, there may not be any virus on the swab in which case the test will be reported as "virus not detected".

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IgG Antibody Tests

This tests your blood for the presence of antibodies that your body has produced in response to being exposed to the virus. It is only very recently that reliable tests for the presence of antibodies have been made available here. The gold standard so far is the PHE approved, FDA EUA approved reagents we use, millions of which are being shipped to the NHS here, to Europe and the world to be used in the frontline of detecting the spread of SARS-Cov-2 coronavirus through our communities.

There is however still a great deal to learn about this virus. Despite the accuracy of the test there is still much to learn about what is safe behaviour after finding out your result. It is most definitely not recommended that anyone assumes they have immunity and can go about life as what used to be normal before this pandemic just because there are antibodies in their blood.

The test has so far been shown by the FDA to be 100% sensitive in detecting antibodies 14 days after the first symptoms of confirmed SARS-CoV-2 infection* but it is not yet known whether antibodies definitely do give immunity and if they do, for how long. So do not throw away the hand gel and start hugging people who cough just yet!

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In Summary:

If you want to know: 

  • if your symptoms are being caused by covid-19
  • whether you or your family have been exposed to covid-19 and have the actual virus lurking in their noses and throats; and whether they need to self-isolate for the full 14 days and contact all their contacts -

Then it is the PCR test which you should have.  

If you want to know:

  • if the fever and illness you had over 14 days ago was likely to be covid-19

Then it is the IgG antibody blood test you need.