How the tests work
PCR Swab Test
This test is a swab of the back of the mouth (tonsils and pharynx) and the nose. It is most accurate when done by another person, preferably a healthcare professional so we do recommend coming to our drive-through service at our site in Putney, London and having one of our skilled swabbers do it for you. This ensures the lowest chance of a false negative result and the fastest turnaround times. However it can be done by yourself if necessary with proper care and attention. It is important to follow the instructions to ensure that there is the best chance of the test finding whether the virus is there or not.
Your sample is analysed using the latest PCR technology in conjunction with our partner laboratories. It is a molecular assay based on the detection of the viral nucleic material (RNA) within the covid-19 coronavirus.
You will usually get your results, which will confirm whether or not there has been any virus found on your swab, by late in the evening of the day after you have your swab delivered to our laboratory. This turnaround time can not be guaranteed as with such a sensitive test there are always a small percentage that have to be rerun, but we have achieved it 97% of the time.
If your result comes back positive (ie confirming that there is covid-19 RNA on your swab) then you can be very sure that you have coronavirus in your nose or throat. The implications of this, whether you feel ill or not, is that you may be able to spread the virus and you should check the latest NHS advice here: https://www.nhs.uk/conditions/coronavirus-covid-19/. This is particularly the case if you feel unwell or short of breath at all in which case you should go straight to https://111.nhs.uk/service/COVID-19/ where you will find what to do next.
If you get a negative result (ie confirming that no covid-19 RNA was found on your swab) then it is cautiously good news but does not completely guarantee that you have not been exposed to covid-19. All it definitively confirms is that there was no covid-19 on the swab. There is between 70%-95% sensitivity rate with getting the virus on the swab depending on the swabbing technique. This means that there is up to a 30% chance that you did not get swabbed effectively enough – so if you do begin to feel any of the symptoms of covid-19 coronavirus please seek help.
It is worth noting that the PCR test is not the best test for checking whether you are infective or not. The PCR test can detect fragments of viral DNA some weeks after someone's levels have dropped below the amounts of virus that are needed to be infectious to others. A better way to quickly check if someone is infectious is the Rapid Antigen Test.
Rapid Antigen Test - Results in 15 minutes
These tests detect viral protein fragments and return results within 15 minutes.
This test is ideal for quickly checking whether people are infectious and at risk of spreading the virus. Perfect for workplaces, film sets and any other situations where it is important to regularly check whether people are going to be spreading the virus to anyone else.
With results available in 15 minutes it is possible to know very quickly whether your people are likely to be infectious which is the most important information needed to reduce the spread of the virus and keep people safe from being infected.
Rapid Antigen Results
Your results will be given to you at the time of testing - within 15-20 minutes, and a certificate will be sent to you via email soon after.
The Abbott Panbio Antigen Rapid Test that we use has shown a 98.2% sensitivity in detecting viral levels that are currently considered to be infectious (Ct values < 33). It has an overall sensitivity and specificity agreement with RT-PCR results of 97.9%. It has a reported specificity of 99.4%.
A positive result has a very high chance of confirming if you are carrying covid-19 virus in enough quantities to make you infectious. A negative result gives a very high likelihood that you are not infectious. Regular testing is recommended to ensure that this remains the case every time you intend to be in close contact with anyone.
IgG Antibody Test
This tests your blood for the presence of antibodies that your body has produced in response to being exposed to the virus. It is only very recently - in April, that reliable tests for the presence of antibodies have been made available here. Our IgG test is PHE approved and produced by one of the world's foremost diagnostic providers, millions of which are being shipped to the NHS here, to Europe and the world to be used in the frontline of detecting the spread of SARS-Cov-2 coronavirus through our communities. It is PHE evaluated, FDA EUA approved and CE marked.
You will get your results within a day of your blood sample being received here at our laboratory. Your result will let you know whether IgG antibodies have been detected or not.
This test has been shown to be between 96% and 100% sensitive in identifying antibodies to SARS-CoV-2 coronavirus at 14 days after onset of covid-19 symptoms*. Or put another way, everyone who had an illness that was confirmed to be caused by covid-19 developed IgG antibodies 14 days later so there were no false negatives.
It is 99.63% specific. Or put another way, Only 0.37% of over 1000 people tested who could not have been exposed to SARS-CoV-2 showed a false positive result. Interestingly there were over 70 people who had other similar respiratory illnesses tested in this group and none of them showed any false positives so it seems very unlikely that this test picks up antibodies to any of the other viruses that cause symptoms like covid-19. This problem with cross-reactivity was a very major concern about many of the cassette tests that were rushed to market.
It is PHE approved, CE marked, FDA EUA approved, and is being shipped to laboratories in the UK and Europe in the millions of units to be used in the frontline of testing efforts to track the spread of the virus through our community.
We are working with the world leader in developing SARS-CoV-2 testing and it is exciting to be one of the first laboratories in Europe able to make this particular test available to anyone who would like to know more about their exposure to this virus
Please note that there is still a lot to learn about this virus and having antibodies does not mean you definitely have immunity. Also, it is not yet clear how long immunity lasts, even if there is any. So please don't think you can shed the masks, flush the alcogel and rush out to a party just because you get a positive result!
While there is still a lot of uncertainty, it is likely and that you may have at least some temporary immunity. Still, it is very important that you do not take the presence of antibodies to mean that you are able to ignore government advice about social distancing, hand washing and isolation.
Not Competing with the NHS
We also want to emphasise that by providing people with the choice to have these tests we are not in any way limiting the NHS' or Public Health England's ability to provide testing for frontline medical staff or anyone else in the UK. This is an entirely extra service that is available to people who choose to use us and we will be very happy to stop providing the service and go back to our 'day jobs' as soon as there is no need for it and PHE and the NHS have ramped up their capacity to provide enough testing for every individual who would benefit from knowing. We do understand that they are doing everything in their capacity to make this happen as soon as possible and we are doing everything we can to support them in this. Sometimes there are things that a smaller, more nimble organisation can implement more quickly. This is one of those times and we are proud to help where we can.