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COVID-19 Testing

COVID-19 Quantitative Antibody Testing Service and PCR Testing in partnership with Circular 1 Heath

COVID-19 antibody and PCR testing

Having quantitative testing is important as it tells you how strong your immune response to SARS-CoV-2 is. It also gives you a baseline measure so you can check whether your levels have changed over time.

Prof. Sebastian Johnston, Chief Medical Officer and co-founder

COVID-19 antibody and PCR testing


In response to the COVID-19 pandemic, VirTus launched a COVID-19 antibody test, which measures antibodies following COVID-19 infection or vaccination.
We have partnered with Circular One Health to also offer PCR testing, both for domestic and travel use.

To buy a COVID-19 antibody or PCR test, please visit our shop

To find out more about our testing services for GPs, businesses or large groups, please contact us at

Why choose the VirTus test?

The most informative test on the market

  • Our test is quantitative and will give both a numerical value for the strength of your antibody response and indicate whether your antibody levels are low, medium, high or very high.
  • Repeat testing using this test allows you to monitor your COVID-19 antibody levels over time, which are known to decrease at different rates in different people.
  • Our tests measures both COVID-19 IgG and IgM antibodies. IgM antibodies are detectable earlier than IgG, and most tests only measure IgG.
  • A test designed and run by experts in immunology.
  • We will soon have antibody tests for COVID-19 variants.

Why do we test for antibodies?

Antibodies are proteins that our immune systems produce in response to pathogens, such as viruses. Antibodies recognise and attach themselves to specific viruses. This blocks virus particles from entering our cells, meaning they cannot use our cells to multiply and spread within our body, causing symptoms and transmission.

If a person has previously been infected with SARS-CoV-2 (the virus that causes COVID-19) or received the COVID-19 vaccine, they are likely to have antibodies in their blood. IgM antibodies are produced first by our immune system and are followed by IgG antibodies, which tend to be longer-lasting (see diagram below). Our test detects these antibodies in blood samples, which provides some indication of a person’s susceptibility to future infection.

Why is this important?

This will help you understand the strength of your immunity to COVID-19 and how well you may have responded to the COVID-19 vaccine. Monitoring antibodies levels over time is useful as these decline at different rates in different individuals.

Are the antibodies that our test detects protective against COVID-19?

When compared against a SARS-CoV-2 neutralisation test, antibodies detected by our test were shown to block the SARS-CoV-2 virus from infecting cells. IgG & IgM antibody levels measured by our test correlate very strongly [r=0.7, P<0.0001] with virus neutralisation activity.

How accurate is this test?

Accuracy for these tests is discussed in terms of sensitivity, which is the likelihood of false negatives (receiving a negative result, when this should be positive) and specificity, which is the likelihood of receiving a false-positive result (receiving a positive result, when this should be negative). For the VirTus test:


  • This test has been shown to detect 100% of severe hospitalised cases and 86.9% of 107 milder community cases, including asymptomatic people with a positive SARS-CoV-2 swab test. Most other tests have been validated in hospital cases and not in community or asymptomatic cases of COVID-19.



  • For high or very high positives, the specificity of our test is 100%. This means for moderate to very high antibody positives, we are almost 100% certain they are not false positives.
  • For moderate level positives, the specificity of our test is 99.5%. This means for moderate antibody positives, one in 200 tests could be a false positive.
  • For low-level positives, the specificity of our test is 98.6%. This means for low antibody positives, 1.4 in 100 tests could be a false positive.

Note that in Prof Johnston’s view, a “false positive” is likely to be showing cross-reactive protection from prior seasonal coronavirus exposure.

What does my antibody test result mean?

Receiving an overall result of “Positive” from our test confirms that you have either had a prior COVID-19 infection or received a COVID-19 vaccine and you have mounted an immune response against the virus that is detectable by our test. A positive result for either IgM or IgG gives an overall positive result.

An overall result of “Negative” means that any IgM or IgG antibodies to the SARS-CoV-2 S1 spike protein were not detected by our test. This could be because:

  • You have not previously been infected or vaccinated against COVID-19
  • You have been infected or vaccinated, but the antibodies you produced are below the detection limit of our test
  • You have been infected but your immune system has produced antibodies that do not bind to the S1 spike protein in our test

How long will my results take?

Results will be delivered via email (usually by 6pm) within 2 working days of receipt of samples in VirTus’ laboratory (Camden, London).

Is this an accredited test?

VirTus tests are CE accredited and registered with the MHRA. VirTus’ laboratory operates under ISO 15189 is undergoing accreditation by the UK Accreditation Service (UKAS).

Further VirTus tests available soon:

  • COVID-19 Delta (Indian) variant test

The COVID-19 vaccines were developed against the original (Wuhan) strain and this test will show how effective your blood antibodies would be against the COVID-19 Delta variant.

  • COVID-19 N protein test

Our current test detects antibodies to the spike (S1) protein of SARS-CoV-2 and this will detect antibodies from both natural infection and vaccination. The N protein (or nucleoprotein) test can show whether you have antibodies from natural infection ONLY, as you will not have antibodies to the N protein following vaccination.




Having quantitative testing is important as it tells you how strong your immune response to SARS-CoV-2 is. It also gives you a baseline measure so you can check whether your levels have changed over time.

Prof. Sebastian Johnston, Chief Medical Officer and co-founder

Would you like to purchase our COVID-19 Antibody Test?

You can now order your home sample kit with FREE Next Day Delivery.


Get in touch

Would you like to know more about our COVID-19 antibody testing service? Please do get in touch.