What is an antibody test?
October 26, 2020
What is an antibody test?
You may have heard a lot about antibody testing for Covid-19 but what is it, how do you get one, and what do the results mean?
Covid-19 antibody tests detect if you have antibodies to the virus. Antibodies are produced by your immune system when you have a disease. So, if you have antibodies, you’ve likely had the virus.
However, these antibodies are only present in some people who have previously had the virus – not in everyone.
Another thing to note is that a Covid-19 antibody test is not the same as a PCR test (also called a swab test). A PCR test looks for viral DNA or RNA in your body at the time of testing, and tells you if you currently have the virus, not whether you’ve had it in the past. Antigen tests are another type of test - they look for various proteins that are part of the virus. These tests are currently not readily available as they are less sensitive.
How is a Covid-19 antibody test conducted?
At the moment, one of the only Covid-19 antibody testing methods approved by the Government’s Medicines and Healthcare products Regulatory Agency (MHRA) is for a trained healthcare professional to take a blood sample from a patient – also called a venous blood test. The sample is then sent away for analysis to test for the presence of antibodies.
This is the method we use at Melio.
What results will I get?
At Melio, we use a blood test developed by Siemens which studies have shown to be the most accurate test available. Our test gives you a simple straightforward ‘positive’, ‘negative’ or ‘void’ result.
What does a positive Covid-19 antibody test result mean?
If you get a positive result from your Covid-19 antibody test it means it did detect Covid-19 antibodies in your blood. This means it is likely that you have had the Covid-19 coronavirus, even if you don’t remember having any symptoms or feeling unwell.
What does a negative Covid-19 antibody test result mean?
A negative result means the test did not detect Covid-19 antibodies in your blood. This means your immune system has not mounted an antibody response to Covid-19, but it doesn’t necessarily mean that you have not been infected with Covid-19 just that you don’t have antibodies against the virus. Your immune system has other ways of responding to viruses, like T cells.
However, in some cases it is possible to get a negative result even if you know you have had the virus before. This can happen because some people simply do not develop antibodies, or their level of antibodies is too low for the test to detect.
What does a void Covid-19 antibody test result mean?
If you get a void result it means the test did not work. There are a variety of reasons for this, such as a problem with the testing kit, or possibly the sample itself being too small.
What are IgM and IgG antibodies?
Other Covid-19 antibody tests show results for levels of two types of antibodies called IgM and IgG. IgM antibodies are made by the body in the early stages of infection, and can last up to a month. IgG antibodies are produced later – after around 21 days – and could last for months, possibly years. If your test results show either or both of these it means the result is positive. If neither of these antibodies are present, the result is negative.
The Siemens test we use at Melio gives a simple positive/negative/void result. Studies have shown it to be the most accurate.
How accurate are Covid-19 antibody tests?
You will hear test accuracy referred to by two concepts expressed as percentages: sensitivity and specificity.
Sensitivity is the ability of the test to correctly generate a positive result for people who have antibodies.
Specificity is the ability of the test to correctly generate a negative result for people who don't have any antibodies.
The MHRA currently requires Covid-19 clinical antibody tests to have a minimum standard of sensitivity and specificity of greater than 98% (see here).
The Siemens Covid-19 total antibody test that we use at Melio has sensitivity of 98.1% and specificity of 99.9%.
What a Covid-19 antibody test can’t tell you
So far there is no conclusive evidence to suggest that people who have had Covid-19 develop long-lasting immunity that will stop them getting the virus again.
This means that testing positive for Covid-19 antibodies cannot tell you:
if you’re immune to further infection from Covid-19
if you can or cannot spread the virus to other people
when you had the virus
What happens once I get my result?
Even if you test positive for antibodies, you must still follow national Covid-19 guidelines to protect yourself and others from the virus including:
frequent hand washing
following social distancing rules
wearing a face covering where required
abiding by local lockdown restrictions in your area
following the rules on when to get tested and when to self-isolate
Check your Covid-19 antibody status today
If you want to find out if you’ve had Covid-19 and would like to know if you have antibodies, you can book a fast and accurate antibody test at one of our growing number of convenient locations today.
Order and pay for your test online, book an appointment at a time and place that suits you, and receive the results directly to your mobile within 24-48 hours. All test results are individually checked by one of our in-house doctors and sent directly to you with a personal medical report which includes any further advice and signposting you may need.
If you are ready to book your Covid-19 antibody test click here: https://www.meliohealth.co.uk/product/covid-19-antibody-test, or use the chat button if you’d like to talk to one of our specially trained advisors for more information.