Please find below answers to frequently asked questions. If we have not answered your question, please get in touch with us by replying to your results email.
Why are you studying twin pairs?
We are studying both identical and non-identical twin pairs. Identical twins share 100% of their genes while non-identical twins share about 50% of their genes.
By studying twin pairs, we can learn more about how individual responses to COVID-19 depend on genes and environmental and lifestyle factors.
Comparing responses between twins in a pair and more broadly across all twin pairs helps us to understand more about how the virus behaves and how our bodies respond to it.
What is the difference between the nasal swab and the antibody blood test?
The nasal swab looks like a cotton bud and the test is carried out by gently swabbing inside the nose or the back of the throat. We use the nasal swab to detect any active traces of the virus that causes COVID-19.
The antibody test is carried out by analysing the blood collected from your arm. We use the antibody test to detect whether you have had a clear immune response to the virus that causes COVID-19.
My swab came back positive. Does this mean I can pass COVID-19 onto others?
A positive swab result indicates that you had some traces of the virus responsible for COVID-19 at the time of testing. We do not know if you are still infectious and able to pass the virus onto someone else. Please be aware swab testing results can change from day to day from when the virus first infects an individual.
We encourage you to let your GP know that you tested positive for traces of COVID-19 from the swab taken at your home visit. Please check whether you, and anyone living with you, have self-isolated in line with NHS guidance. You may need to be tested again by the NHS in the future.
You may also wish to consider informing your employer.
My swab came back negative, but I previously had symptoms consistent with COVID-19. What does this mean?
This could be because:
- The symptoms you experienced were the result of a flu or other standard bug, and you have not been infected with COVID-19.
- You may have been exposed to COVID-19 but at the time of testing, your body no longer had active traces of the virus.
Please be aware swab testing results can change from day to day from when the virus first infects an individual.
It may be that you will need further swab tests if you develop symptoms again later on.
My swab results were invalid. What does this mean?
The nasal swab at the home visit did not collect enough sample material for us to analyse. This means we have not been able to produce a valid result for this test.
The way the test is carried out means that it is not always possible to tell just by looking at the swab whether enough of the relevant material has been collected, and we can only know this once the swab is sent for analysis. We do apologise for any inconvenience caused.
My swab results have changed between negative/positive at the different visits. Do I have COVID-19 or not?
Please be aware swab testing results can change from day to day from when the virus first infects an individual.
A positive swab result indicates that you had some traces of the virus responsible for COVID-19 at the time of testing. Please check whether you, and anyone living with you, have self-isolated in line with NHS guidance. You may need to be tested again by the NHS in the future.
We encourage you to let your GP know that you tested positive for traces of COVID-19 from the swab taken at your home visit. You may also wish to consider informing your employer.
How is this swab test different from the government/NHS one?
The government swab tests are analysed in NHS-approved labs that produce clinical-grade results – this means that the results can be used to make decisions about a diagnosis and appropriate treatment.
By contrast, this swab was collected and carried out as part of a research study and analysed in a research lab at King’s College London. The results from these swab tests are for research purposes only and cannot be used to confirm a current or previous diagnosis of COVID-19.
What is the sensitivity and specificity of the swab test?
Sensitivity is 70-80% due to variation in sampling technique at the point of swabbing. Specificity is 100% based on the fact that the primers we use for SARS-COV-2 are unique to this virus. This means we do not get positive results for different types of coronaviruses.
What is the sensitivity and specificity of the antibody test?
Based on the thresholds we are using, the test is 100% specific. The sensitivity depends on the days post-onset of symptoms and is related to the kinetics of antibody production. At greater than 20 days post-onset of symptoms it is 96.4% sensitive, at greater than 14 days it is 87.0% and then at greater than 10 days it is 84.7%.
My swab was positive for COVID-19 and I also had clearly detectable levels of antibodies. What does this mean?
In some cases, individuals continue to have active traces of the virus that causes COVID-19 for weeks after their immune system has developed antibodies against it.
A positive swab result indicates that you had some traces of the virus responsible for COVID-19 at the time of testing. We do not know if you are still infectious and able to pass the virus onto someone else. Please be aware swab testing results can change from day to day from when the virus first infects an individual.
We encourage you to let your GP know that you tested positive for traces of COVID-19 from the swab taken at your home visit. Please check whether you, and anyone living with you, have self-isolated in line with NHS guidance. You may need to be tested again by the NHS in the future.
Regarding the clearly detectable antibodies, at this time, doctors and researchers do not know whether antibodies have any meaningful effect or offer protection against re-infection. You should continue to follow all guidance on self-isolation and social distancing as appropriate.
I had clearly detectable levels of antibodies. Does this mean I am now immune to COVID-19?
At this time, doctors and researchers do not know whether antibodies have any meaningful effect or offer protection against re-infection. You should continue to follow all guidance on self-isolation and social distancing as appropriate.
My antibody test results say I do not have clearly detectable antibody levels, but I previously had symptoms consistent with a COVID-19 infection. What does this mean?
This could be because:
- The symptoms you experienced were the result of a flu or other standard bug, and you have not been exposed to COVID-19.
- You may have been exposed to COVID-19 but at the time of testing, your body had not mounted a clear immune response to the virus.
You should continue to follow all guidance on self-isolation and social distancing as appropriate.
My antibody results have changed from not clearly detectable to clearly detectable between visits. What does this mean?
We believe this means that your body has mounted some level of immune response due to a COVID-19 exposure or infection. It can take some time for the immune system to produce clearly detectable levels of antibodies in response to an infection.
At this time, doctors and researchers do not know whether antibodies have any meaningful effect or offer protection against re-infection. You should continue to follow all guidance on self-isolation and social distancing as appropriate.
My antibody results have changed from clearly detectable to not clearly detectable between visits. What does this mean?
We believe this means that previously your immune system had produced antibodies in response to a COVID-19 exposure or infection, but that immune response may have declined over time.
Evidence suggests that individuals’ immune systems respond differently and at this time, doctors and researchers do not know whether having antibodies gives individuals any lasting protective effects against re-infection.
My twin and I have been living together and one of us had clearly detectable antibodies and one of us didn't. What does this mean?
- It may be that one twin was exposed to COVID-19 and developed antibodies, but the other was not infected and so did not develop antibodies.
- It may be that you both were exposed to COVID-19, but one twin did not develop a clearly detectable level of antibodies.
- It may be that you both were exposed to COVID-19 and you both developed clearly detectable antibodies, but by the time of your home visit, one twin’s antibody levels had declined to a not clearly detectable level.
I understand that the government approved an antibody test on the 14th May 2020. What antibody test are you using?
When we started this study, there was no government or NHS-approved antibody test. We are using an antibody test developed by King’s College London researchers. This means that any results given from this test are for research purposes only and cannot be used to determine a previous or current case of COVID-19, as they come from a research lab only, not a clinical-grade NHS lab.
In the future, we may use the government-approved test alongside or instead of our King’s College London one.
Will I get any results from the stool and saliva sample collected at the visit?
Thank you for providing these samples. We have collected these sample for future analysis to understand how the virus responsible for COVID-19 behaves and how the body responds to it. At this time, it is not possible to get any results from them that are meaningful for your health.
Do I have to tell anybody about my test results?
These results are private to you, although you are free to share them with others if you wish.
Please bear in mind that these are research tests only, and we are not able to confirm a clinical diagnosis of a current or previous case of COVID-19 from them, as the results are from a King’s College London research lab, and not an NHS clinical-grade lab.
If you test positive for the nasal swab, we encourage you to let your GP know that you tested positive for traces of COVID-19 from the swab taken at your home visit. You may also wish to consider informing your employer.