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Coronavirus Antibody Blood Test

A laboratory blood test can tell you whether you’ve already had COVID-19. Find out how a coronavirus antibody blood test works and how to get one.

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Important – posting your sample to the lab

Important – posting your sample to the lab

Royal Mail is not accepting any Covid-19 samples at post office counters or non-priority postboxes. All samples must be posted in a priority postbox.

 

This is because the postal workers collecting from priority postboxes have the proper PPE (personal protective equipment) in order to safely handle the samples. Your return envelope will have a sticker identifying it as a Covid-19 sample.

 

You can find your nearest priority postbox here.

How can i buy a coronavirus antibody test?

Coronavirus antibody tests with venous sample collection available from Medichecks

You can buy a coronavirus antibody blood test from Medichecks provided your sample is taken by a health professional from a vein in your arm (a venous sample). We have tests with two sample collection options available. You can make an appointment to visit one of our network of private clinics to have your blood sample taken, or your can buy a test which includes a nurse home visit. Simply choose which sample collection option you want, buy the test and visit my.medichecks.com to select your nearest clinic or make an appointment for a nurse to visit you at home.

Can I buy a self-collect finger-prick test?

On May 26th, the Medicines and Healthcare products Regulatory Agency (MHRA) wrote to private laboratories in the UK asking them to pause the processing of self-collect finger-prick samples for coronavirus antibody testing. The MHRA made this request so that they could undertake a review of the end-to-end testing process. We believe this is to ensure that home sample collection with postal delivery to the laboratory is a safe and accurate way of testing coronavirus antibodies.

We are confident that this service will resume shortly once the laboratories have completed their validation studies.

Has the MHRA paused private testing on venous blood samples?

No, there are no restrictions placed on private laboratories testing samples which have been taken from a vein in the arm.

Do the same restrictions apply to at-home rapid detection antibody tests?

The MHRA review applies to tests where you collect a finger prick blood sample at home in a small vial and post to a laboratory for analysis. Normally you would expect to receive a laboratory test result within 2 or 3 days of a laboratory receiving your sample. This is not the same as the rapid detection tests which give you a result within minutes. So far, none of the rapid detection tests have been able to achieve the levels of accuracy reported by the manufacturers of laboratory tests and no rapid detection cassette kits have been approved for use by Public Health England.

Coronavirus Antibody FAQs

How do coronavirus antibody tests work?

Coronavirus antibody tests look for the presence 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 from 14 days after the onset of symptoms. Although some laboratories advise waiting for 21 days after the onset of symptoms, recently published evaluations by Public Health England on the antibody tests manufactured by Roche (1) and Abbott (2) saw only a very small increase in detectable antibodies between 14 and 21 days, with sensitivity increasing by less than 1% in both cases. Antibody tests help to establish whether someone has had COVID-19 and is now producing antibodies to the virus.

Does a positive antibody test mean that I now have 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.

If I have a positive coronavirus antibody test result, do I still need to follow the government guidelines for social distancing?

Yes, until we understand more about the virus and whether the presence of antibodies means that you can’t catch it again, it is important that you follow all the recommended guidelines.

How are coronavirus antibody tests carried out?

To-date, the most reliable antibody tests are performed in pathology laboratories using tests supplied by large global medical devices manufactures, Abbott and Roche. These are laboratory immunoassays which have been approved by Public Health England who have recently published their own evaluation of these tests (1) (2).

How accurate are coronavirus antibody tests?

Most private laboratories are using the Abbott test which has been both CE marked and approved by Public Health England. The test 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. It is important to note that the manufacturer’s validation study was conducted on venous blood samples taken from a vein in the arm. Laboratories are now working on their own validation studies which will allow them to produce their own true positive and true negative rates for the test. 

Coronavirus Antibody Test Result FAQs

What does a positive result mean?

A positive result means that the laboratory found IgG antibodies to coronavirus (SARS-CoV-2) in your blood. This means that it is highly likely that you have been infected with coronavirus in the past.

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 Abbott, about 1 test in every 200 on samples from people not infected with coronavirus returned a false positive result.

What does a negative result mean?

A negative result means that the laboratory did not find IgG antibodies to coronavirus (SARS CoV-2) in your blood. This means that it is very unlikely that you have been infected with the virus in the past. However, you may get a negative result if you took the test too soon after developing symptoms (i.e. before antibodies have reached detectable levels). This is why it is important to wait at least 14 days from the onset of symptoms before taking your test.

Could there be false negative results?

The Abbott 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. There may be scenarios where an antibody test is negative but the individual has been infected with coronavirus. See below for further details.

Can I get a negative antibody result even if I have had covid-19 infection?

There is a small possibility that you have had coronavirus yet have not developed antibodies. This can happen if you had a very mild case of COVID-19 or did not develop any symptoms. There is also some emerging evidence that a minority of people who had a negative antibody result may have had a different type of immune response controlled by T cells, a type of white blood cell that recognises infected cells. Our test measures IgG (immunoglobulin G antibodies) which is the most common type of antibody found in the blood after an infection. As our immune systems are highly complex and this virus is novel, it takes time for the global medical science community to develop the best understanding of COVID-19 immunity. More recently research from the Karolinska Institutet in Sweden found that people with mild or no symptoms had developed “T-cell” immunity despite testing negative for antibodies. This study is yet to be published and peer reviewed by the science community, but it has no doubt provoked further debate about how our immune systems respond to the virus. Before we can jump to any solid conclusions, further evaluation of this is needed with more research. Until we know more about whether antibodies or T-cells confer any protection against coronavirus, it is not safe to assume that you have acquired immunity to COVID-19.

Is my negative test result reliable if my suspected infection was over 2 months ago?

If you develop an antibody response to the virus, it is most likely to show up as a positive result 2-3 weeks after the onset of symptoms. Further research is currently being conducted to confirm what happens to these antibody levels beyond 5 weeks. At present we are not in a position to reach any clear conclusions as whilst some studies have shown the antibody response can disappear after 2-3 months, others have concluded this can last for longer than 2 months. In short, a negative antibody result cannot completely rule out a previous infection.

Since the first case of COVID-19 was first reported to the World Health Organisation in December 2019 knowledge about this virus has been ever evolving. Research is ongoing and there is still much more to learn about the long-term effects of this virus on our health and immunity. It is also important to note that amidst our focus on this pandemic we must not forget that the symptoms of coronavirus can be caused by other viruses, allergies and medical conditions. If you are still experiencing symptoms which cause you concern, we recommend you discuss them with your GP.

What does a borderline result mean?

Some laboratories also report borderline results. Borderline results mean that IgG antibodies were not high enough to give a positive result. This may be because you tested too soon after developing symptoms. If you get a borderline result, we suggest repeating the test 7-14 days after your first test to check if your antibody levels have increased.

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