What kind of test is this?
This test looks for the presence of immunoglobin G (IgG) antibodies to SARS-CoV-2, the virus that causes the COVID-19 illness. Antibodies are produced by the body's immune system during COVID-19 and start to become detectable around 7 days after symptoms start and increase over time. Antibodies can be reliably detected in the majority of people 14 days after the onset of symptoms. This test helps to establish whether someone has had COVID-19 and is now producing antibodies to the virus.
Does a positive antibody test mean that an individual now has immunity to COVID-19?
We do not yet know whether the presence of antibodies to SARS-CoV-2 in the blood provides any lasting immunity to future infection or any protection at all. We expect to learn more about the extent and duration of any potential immunity over the coming months.
How is the test carried out?
The test is performed on a blood sample by our UKAS-accredited laboratory partners using a CE-marked antibody test. It is a laboratory test using chemiluminescent microparticle immunoassay (CMIA) technology, developed by a global medical devices manufacturer and health care company. The fact that it is CE-marked means that it conforms with European standards for the design and manufacture of such tests.
How accurate is the test?
The manufacturer states that in its validation study the test detected antibodies in 100% of confirmed coronavirus cases when the sample was taken at least 14 days after symptoms first developed. The test produced a negative result in 99.6% of samples from people who did not have the SARS-CoV-2 infection in the same study.
Why has Medichecks decided to sell a Coronavirus antibody test?
We have been working closely with our partner laboratories to find an antibody test which is both accurate and available at scale. While other tests have been available for a few weeks, this test reports higher levels of accuracy than these tests currently available. We wanted to wait for a test that could be relied upon for an accurate result before launching a test to members of the public.
Is it the same as the at-home rapid detection antibody tests?
No, this is a test where you collect a finger prick blood sample at home in a small vial and post it to our UKAS-accredited laboratory for analysis. Once the laboratory receives the blood sample, your result should be available within 3 days. So far, none of the rapid detection tests have been able to achieve the levels of accuracy claimed by the manufacturer for this laboratory test.
Could there be false positive results?
Most tests that look for antibodies will return a small percentage of false-positive results. In the case of SARS-CoV-2 they may occur because antibodies to other viruses in the coronavirus family potentially react with the components in the SARS-CoV-2 antibody tests. In the validation study conducted by the manufacturer, about 1 test in every 200 on samples from people not infected with coronavirus returned a positive result.
Could there be false negative results?
This coronavirus antibody test was 100% sensitive in its validation study. This means that it correctly detected antibodies to SARS-CoV-2 in all samples from people with a confirmed coronavirus infection and who were tested at least 14 days after the onset of symptoms. If you test before this time, you may get a negative result even if you are infected, because your antibodies may not yet have reached detectable levels.
How does it work?
This test is only available as an intravenous blood sample collection. You can either visit one of our partner clinics for the blood draw or alternatively, you can opt for a nurse home visit. We will then send you a Medichecks venous kit and further instruction on email on what to expect next. Unlike the at-home cassettes, individuals are not required to interpret their own results. We provide doctors comments with all results.
Who should use this test?
This test is appropriate for anyone who wants to know whether they have had COVID-19. People who have had a mild or moderate form of the disease, or who have been exposed to COVID-19 but didn’t experience symptoms at all, may want to know whether they previously had the virus. It is important to wait 14 days from the onset of symptoms before taking this test; this allows sufficient time for antibodies to reach detectable levels. If you have had no symptoms, then this test should be taken 21 days after the last exposure to the virus.
How can companies use this test?
This test can be used by companies or organisations that want to find out whether any of their employees have already had COVID-19. It may be useful for companies planning a staged return to work for key staff. It is not known yet whether the presence of antibodies confers immunity to coronavirus in the future.
Will this test tell me if I have a current infection?
No, this test detects antibodies which are produced some time after an individual becomes infected. Antibodies normally reach detectable levels 14 days after developing symptoms, or 21 days after last exposure to the virus.
What is a PCR test?
Most tests conducted for COVID-19 to date are polymerase chain reaction (PCR) tests, which look for genetic (RNA) fragments of the virus itself. These swab tests are used to collect samples from the nose and throat in drive-through testing centres which have been set up for front-line NHS and other key workers. These tests look for an active infection. A positive PCR test means that you currently have the virus and are potentially infectious to others.
Why doesn’t Medichecks sell a PCR swab test?
We have decided not to sell an at-home swab test for COVID-19 because of the challenges of completing self-collect swab samples. The swab needs to be inserted deep into the nose and towards the back of the throat for a reliable sample to be collected. If the sample isn’t taken correctly, the chances of a false negative result (being told that you are not infected, when in fact you are) are unacceptably high.