What do my results mean?
There are a range of results that service users can receive. The SHL.UK team are available to discuss results by phone and support you getting treatment or having further testing. If you don’t feel comfortable receiving results in this way, you should visit a sexual health clinic where you can be tested and have a face to face discussion about your results.
- Negative means the infection was not identified.
- Positive means the infection was identified. The SHL.UK team will advise you how to get treatment. This may be via our remote treatment service (for chlamydia) or by attending a sexual health clinic (for gonorrhoea).
- Reactive usually applies to the blood tests (HIV, syphilis or hepatitis B or C) and means the initial screening test was positive and you require further testing. At the point of further testing some people test negative for the infection whereas others may be confirmed positive, indicating they have the infection. Because we only are able to work with small blood samples, SHL.UK is limited in terms of what additional tests we can perform – for this reason we may encourage you to attend the sexual health clinic. If you test positive at the sexual health clinic, they can treat you (for syphilis) or refer you to a hepatitis clinic or HIV outpatient service for ongoing care.
- SHL provides two kinds of reactive result for blood tests for HIV, hepatitis B and hepatitis C: these are low reactive and reactive. It is very unusual for a low reactive HIV or low reactive hepatitis result to be confirmed in clinic as a true positive infection. However, a small number of individuals (fewer than 1%) do have a very new infection. The SHL team will talk to you about your reactive (or low reactive) result and clinically assess you before advising your next steps. For some people with low reactive results, we can send you another self-testing kit to re-test if you prefer (instead of going to clinic). For others we will recommend testing in clinic. The team can also help you be seen in the sexual health clinic if you are having difficulty attending for confirmatory blood tests. *More detailed information about reactive results can be found below.
- Inconclusive/Equivocal means the result is not clear cut and further testing is advised. In these situations, you can contact SHL.UK for a new kit or attend a sexual health clinic.
- Haemolysed means the blood sample you provided haemolysed during transit and was not able to be tested. Haemolysis is caused by blood cells in the sample bursting open – this can either be caused in transit due to being shaken in the post, or hot/cold weather, or due to squeezing the finger too hard when collecting the sample. It is a normal process for blood to go through, so is nothing to be concerned about. In this situation you can request a new kit yourself via your account or by contacting SHL.UK. Alternatively attend a sexual health clinic to test there. If you want another kit, please read the helpful tips on taking your blood sample before trying again.
- Insufficient usually applies to the blood tests and means there was not enough of a sample provided. In this situation you can request a new kit yourself via your account or by contacting SHL.UK. Alternatively attend a sexual health clinic to test there. If you want another kit, please read the helpful tips on taking your blood sample before trying again.
- Out of protocol or Out of validation results refer to a number of problems that mean we cannot provide a result for you: samples lost or damaged or not collected properly; too much time had lapsed between the sample collection date and when they were received in the lab; another laboratory problem. In this situation you can request a new kit yourself via your account or by contacting SHL.UK. Alternatively attend a sexual health clinic to test there.
If you ever feel confused or the information available to you is unclear you can contact the SHL.UK team on 0208 191 0222 and they will happily go through this with you.
Reasons for you might receive false positive / false reactive results from SHL
SHL uses high quality, accredited tests that are extremely reliable, however, no test is 100% accurate all the time. This means regrettably there will be a small number of people with an infection who receive a negative result (false negative) and a small number of people without an infection that are given a positive/reactive result (false positive/reactive).
When using online testing services, it is possible you may be marginally more likely to receive a false positive result compared to being tested in a clinic setting. This is because with bigger blood samples taken in clinic, after a reactive HIV or hepatitis result the clinic’s laboratory will usually perform immediate follow up tests to confirm the true outcome before giving you the result. These extra tests cannot be provided with the finger prick samples provided within online services, meaning you will be encouraged to attend clinic so a larger sample of blood can be taken and tested more extensively.
We appreciate receiving false reactive/positive or false negative results can be distressing. The SHL.UK team can support you should you receive such results. For further advice or if you have any questions contact the team on 0208 191 0222.
*More detailed information about false reactive results can be found below.
I do not think my test results are correct, what should I do?
Sometimes an individual may receive a different test result when they get tested at another testing provider e.g. someone receives a positive gonorrhoea test at SHL but then tests negative for gonorrhoea when they attend a sexual health clinic in person. These are called discordant results. Discordant results can be due to a number of reasons which are detailed below. If you are concerned about receiving a discordant result or are unsure whether you should receive treatment or not, please contact the clinical team at SHL on 020 8191 0222.
Reasons for discordant results
Discordant results are when you get a test result through one testing service and then get a different result with another service. This can happen because these services using different types of tests, or different testing platforms.
Sometimes people who become infected with an STI may naturally clear the infection or may receive treatment for another healthcare conditions (e.g. dental infection) which inadvertently treats the STI. Testing either side of this natural clearance or treatment clearance can generate different results.
If you have been recently infected with an STI, it can take a period of time before your test becomes positive. These are called window periods. Window periods differ in length according to the STI in question but it can result in an initial test being negative and a second test a few days later becoming positive. The window period for gonorrhoea and chlamydia is approximately two weeks. Advice about when to perform your tests is available on the SHL.UK site and in the instructions in your testing kit. The time it takes until the test becomes positive after infection can also vary according to what type of test is used. For example, some tests that are performed in a sexual health clinic and sent to a laboratory may turn positive a few days before the finger prick HIV tests do because they have a different window period before detecting infection.
If you test very soon after condomless sex, a positive test result could theoretically be detecting infection in your partners' body fluids. If the STI is not transmitted from your partner to you, then your test result can become negative later.
If someone does not follow the instructions when taking their samples, this can produce a negative result in an infected person. For example, if you pass urine 10 minutes before collecting your urine sample. Conversely if you drop or touch the swab tip whilst self- sampling, this can contaminate your sample leading to a positive result.
SHL, as well as other remote testing services, requires you to post your samples back to a laboratory. This can increase the number of blood samples that haemolyse (clot) and, although we quality check all samples when they are received, sometimes this can cause an incorrect result. Haemolysis does affect samples taken in clinic too but to a slightly lesser degree.
SHL laboratory processes are extremely stringent and overseen by experienced quality, medical and laboratory management teams in accordance with international accreditation. However, sometimes there are problems in the laboratory, and we may undertake an investigation for certain discordant cases.
We are often asked to explain why one partner may test positive for an infection whilst the other partner tests negative. Some of the circumstances above can explain these differences. It is important to check there are no other partners where an STI could have come from. It is also important to ensure the tests you perform are nationally recommended and from an accredited organisation. Again, a discussion with the clinical team can often help identify why there is a difference between you and your partner's results and whether you should consider having treatment.
*More detailed information about test performance and false reactive results.
Performance of a test is in part related to the sensitivity and specificity of the test. Sensitivity of a test is whether it can detect the infection in those that have it, and test specificity is whether it can rule out the infection in those that do not have it. A more sensitive test will pick up more infections than a less sensitive test. A highly specific test will be more accurate in providing a negative result for those who do not have the STI than a test with low specificity.
The challenge is that because no test is 100% perfect this means regrettably there will be a small number of individuals with the infection who receive a negative result (false negative) and a small number of individuals without the infection that are given a positive/reactive result (false positive/reactive).
Even when we use an extremely sensitive and specific test the numbers of individuals experiencing these erroneous results will vary according to how common (prevalent) the STI is in the population tested. A population with a low prevalent STI (like HIV) will result in more false positives/false reactive results than a population with a common/high prevalent STI (like Chlamydia) but on the other hand the higher prevalent population will experience more false negative test results.
When you test larger populations you will inevitably find more individuals will receive false negative or false positive/reactive results purely because of the higher volume of tests performed.
To show this in an example let’s use a HIV test with 99.9% sensitivity and 99.9% specificity. The population being tested has a very low prevalence where 5 people in 1000 are affected (0.5%)
We will test 100,000 people and given the prevalence we know that 500 individuals have HIV infection and the remaining 99500 individuals don’t. The results of our test will show:
- 499.5 people with HIV infection will be correctly identified and receive a reactive result
- 0.5 person with HIV infection will not be correctly identified and receive a false negative result
- 99400.5 people who are HIV negative will be correctly identified and receive a negative result
- 99.5 people who are HIV negative will not be correctly identified and receive a false reactive result
Let’s now use a Chlamydia test with 99.9% sensitivity and 99.9% specificity. The population being tested has a very high prevalence where 100 people in 1000 are affected (10%)
We will test 100,000 people where we know that 10,000 individuals have Chlamydia infection and the remaining 90,000 individuals don’t have chlamydia. The results will show
- 9990 people with Chlamydia infection will be correctly identified and receive a positive result
- 10 people with Chlamydia infection will not be correctly identified and receive a false negative result
- 89910 people who are Chlamydia negative will be correctly identified and receive a negative result
- 90 people who are Chlamydia negative will not be correctly identified and receive a false positive result
Hopefully you can see that the vast majority of people will receive an accurate result but some individuals do not - the population with a lower STI prevalence receive more false reactive/positives compared to the high prevalent population, but conversely more false negatives will be seen in the higher prevalent group.