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
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.
Coronavirus Antibody FAQs
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.
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.
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.
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).
Medichecks uses the Roche coronavirus antibody test which has been both CE marked and approved by Public Health England (PHE). Roche states in its validation study that 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 99.81% of samples from people who did not have the SARS-CoV-2 infection in the same study. The test checks for the presence of IgM and IgG antibodies, and will tell you whether antibodies have been detected but not which type of antibody.
This test may not accurately detect antibodies in people who have compromised immune systems because their antibody response may be slower or weakened. This may affect the reported results above. These people may have immunodeficiency diseases, infections such as HIV, or be taking medications that suppress the immune system.
A negative result does not exclude a current infection particularly in those who have recently been exposed to SARS-CoV-2, or in those who currently have symptoms of COVID-19, because antibodies to the virus may not have reached detectable levels at this point.
Yes. We are now able to offer a coronavirus antibody test with a finger-prick sample collection kit. You can take your own blood sample in the comfort of your home and post it to our laboratory in the envelope we provide. Please note – this is not an at-home rapid detection test that will give you an immediate result.
The laboratory test is manufactured by Roche, a global diagnostics company, and is CE-marked for use with capillary blood samples – i.e. a sample taken using a finger prick – as well as venous samples. Our sample collection kit is also CE marked.
On 26 May 2020 the Medicines and Healthcare products Regulatory Agency (MHRA) asked laboratories in the UK to pause testing for coronavirus antibodies using self-collect finger-prick samples so that the end-to-end testing process could be reviewed. This review is now complete and we are able to offer this test again with finger-prick collection.
Coronavirus Antibody Test Result FAQs
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.
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 Roche, out of every 1,000 people who do not have the infection between 1 and 2 people would receive a false positive result (0.19%).
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.
The Roche 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 the FAQ below for further details.
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.
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.
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.
Coronavirus Vaccine FAQs
We still don’t know to what extent people who have coronavirus antibodies have acquired protection from re-infection. However, while the incidence of coronavirus is rising, there have only been very few recorded instances of people getting COVID-19 twice. This means that it is highly likely that previous infection confers some immunity. However, we still don’t know how long that immunity will last, or what level of antibodies give reliable immunity to coronavirus. So having the vaccination – even if you have antibodies – is the simplest and safest option at the current time.
In our view it is highly unlikely that you will be required to have an antibody test before being vaccinated. For most diseases, vaccines are administered without testing for antibody levels beforehand (except in the case of some booster vaccinations). A vaccine administered on top of naturally acquired antibodies does not pose a health risk. However, if you are in two minds about having the vaccine and wish to know whether you have antibodies to coronavirus from a recent illness, you may choose to have a test to confirm your antibody status.
A coronavirus antibody test is often called the “have I had coronavirus test” because it is the only way to find out whether you’ve had COVID-19 in the past. If you experienced symptoms which weren’t confirmed with a positive PCR test, then an antibody test is still the best way to find out whether they were caused by COVID-19 or were just a seasonal cold. Many people are curious about whether they had coronavirus – if this is your motive it may still be worth having a coronavirus antibody test.
When the body’s immune system fights off a viral infection the immunity it gains is usually more effective and longer-lasting than the immunity gained from vaccination. But several of the coronavirus vaccines in development are messenger RNA (mRNA) vaccines – and these are an entirely new type of vaccine. We do not yet understand how long immunity from mRNA vaccines lasts for, or how effective it is.
Vaccines used for other viral infections rely on growing the virus in a laboratory, and then extracting the proteins needed to stimulate antibody production by the body. This method is slow, and difficult to scale up to produce the volumes of vaccine needed to control the global pandemic. Biotechnology companies have been exploring alternative ways to get our bodies’ immune systems to react to proteins from the virus.
Our bodies produce proteins by sending a message from the cells’ DNA to the endoplasmic reticulum. The endoplasmic reticulum is an incredible piece of cellular machinery which can produce proteins to order. The cell controls which protein it produces by varying the message it sends in the form of messenger RNA (mRNA). The new coronavirus vaccines contain mRNA which instructs our cells to make the spike protein from coronavirus, borrowing our cellular machinery to produce the protein needed for antibody production. The spike protein is the part of the virus which it uses to gain entry to our cells and is also the part which generates an antibody response by our bodies. When our body’s cells produce the spike protein it is recognised by the immune system, and antibody production begins. The mRNA can be produced quickly and safely in laboratories, without needing to grow live coronavirus, so there are efficiency and safety gains to this method.
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