COVID-19 Antibody Test FAQ's

What are antibodies?

Antibodies are proteins that our immune systems produce in response to infectious agents such as viruses. These antibodies identify specific viruses and bind to them, thus blocking them from entering our cells, multiplying and causing symptoms.

If a person has previously been infected with SARS-CoV-2, they are likely to have these antibodies in their blood. Our test detects antibodies in blood samples and provides an indication of a person’s susceptibility to future infection.

Why is this important?

Many COVID-19 cases (people with symptoms caused by infection with SARS-CoV-2) had only very mild symptoms and some people with SARS-CoV-2 infection had no symptoms whatsoever. Going forward, close monitoring of previous infections will be critical to:

  • Understanding the strength of immunity to SARS-CoV-2 that you as an individual may have
  • Helping employees to return to work more safely, with a better understanding of their own risk of SARS-CoV-2 infection and the risk they may pose to others
  • Gaining a better understanding of a workforce’s susceptibility to infection
  • Understanding the degree of immunity to SARS-CoV-2 within a community.

How accurate is this 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, this is the test sensitivity.

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%.

For low level positives, the specificity of our test is 98.6%.

What does my antibody test result mean?

An overall result of “Negative” means that any IgM or IgG antibodies to the SARS-CoV-2 (the virus that causes COVID-19) S1 spike protein that may have been present in your blood sample were not detected by our test.

This could be because:

  • You have been infected, but your immune system has produced antibodies that do not bind to the SARS-CoV-2 S1 spike protein in our test.
  • You have been infected, but the infection was mild and the antibodies you produced are below the detection limit of our test (if you have had typical COVID-19 symptoms, the first two of our three explanations are the most likely explanations)
  • You have not previously been infected.

Receiving an overall result of “Positive” from our test confirms that you have had COVID-19 in the past and that your immune system has mounted a memory immune response against the virus that is detectable by our test – a positive result for either IgM or IgG gives an overall positive result.

For those that are positive, we will also show you whether you have a low, medium, high or very high amount of antibodies to SARS-CoV-2, with a numerical value for your antibody level – indicating the strength of your immune response to SARS-CoV-2. The stronger your immune response to the virus the better, but it is VirTus’ belief that even a low positive antibody level in our test is actually evidence that you have a pretty strong immune response to the virus. This is because the MHRA required all companies developing antibody tests to set their cut-off for a positive test high (to keep specificity high).

Are the antibodies that our test detects protective against SARS-CoV-2 infection?

This test has also been tested against a SARS-CoV-2 neutralisation test and both IgM & IgG antibody levels measured by our test correlate very strongly (r=0.7, P<0.0001) with virus neutralising (blocking viruses from infecting cells) activity.

This means antibodies detected by our test are highly likely to block the virus from entering cells.