This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Self-testing kits for sexually transmitted infections (STIs) could increase diagnoses while reducing costs. In a new study, people took samples from 3 different sites in the body then pooled the 3 swabs in one container. The swabs were analysed in a single test for the common bacterial infections, gonorrhoea and chlamydia.
The researchers concluded that sexual health services could consider providing at-home self-testing kits. They say self-testing may cause less embarrassment for service users, improve uptake, and free up clinicians’ time.
These results come from the Swab-Yourself Trial with Economic Monitoring and Testing for Infections Collectively (SYSTEMATIC). In the first part of the trial, researchers found that people can take their own swabs as effectively as clinicians. They also showed that many infections would be missed by a single swab of the vagina or urine test.
In the second part of the study, people collected their own 3 samples with self-testing kits. They placed the swabs in a single container. A single analysis of the pooled samples cost no more than the current single test.
Current services generally carry out a single test (of urine or a vaginal swab) for most people. They take extra swabs from the throat and rectum (triple-site screening) only for people in high-risk groups.
The research concluded that self-testing kits could be widely used. With this approach, samples from 3 sites in the body are then pooled for a single analysis. The researchers say these kits would allow services to offer triple-site screening to more service users. They would find far more gonorrhoea and chlamydia infections than the current single-site test.
Further information on STIs can be found on the NHS website.
What’s the issue?
Gonorrhoea and chlamydia are the most common bacterial STIs in the UK and worldwide. They spread from person to person during sex or genital contact.
Most people with chlamydia have no symptoms. Many with gonorrhoea also lack symptoms (around 1 in 10 men and almost 1 in 2 women). This means that infections may remain untreated. This can lead to serious, long-term health problems. In women, untreated infections can lead to pelvic inflammatory disease, which is painful and reduces fertility. In men, both infections can cause pain in the testicles.
Gonorrhoea and chlamydia can infect the entrance to the womb (the cervix), the tube that passes urine out of the body (the urethra) and the rectum. The throat and eyes may also be infected.
Standard tests take urine samples or swabs of the vagina or penis. It would be expensive to test everyone in all infection sites. Most national and international guidelines recommend also testing the rectum and throat (triple-site screening) only for groups at high risk:
- men who have sex with men
- women who have received anal sex
- women who have given oral sex.
Research suggests that this approach misses infections. Women may not report anal or oral sex; and infections may have spread. But triple-site samples cost 3 times as much to analyse as single swabs.
A solution would be for people to take their own samples from the 3 areas of their body and place them together in one container. Pooled triple-site samples should cost no more to analyse than a single sample.
Some sexual health services are already pooling triple-site samples, but there are concerns that this could reduce the accuracy of the test. A handful of studies have researched this approach in men who have sex with men, but none have looked in women.
The SYSTEMATIC study aimed to work out whether triple-site pooling for women and men who have sex with men is a reliable way of diagnosing gonorrhoea and chlamydia.
What’s new?
The SYSTEMATIC trial included 1,284 women and 509 men who have sex with men. All attended a sexual health clinic in Leeds. Some 116 (9%) tested positive for gonorrhoea; 276 (15%) for chlamydia.
The first part of the trial found that self-taken swabs of throat and rectum gave diagnoses as accurately as swabs taken by clinicians. The study also found that it was cheaper for people to take their own swabs at home than for clinicians to take the swabs in a clinic.
It also found that many infections would have been missed by a single swab of the vagina or urine test. Single swabs missed 100 gonorrhoea and chlamydia infections out of a total of 392. Furthermore, the most common site for chlamydia infections in women was the rectum, regardless of whether they reported having anal sex.
The second part of the SYSTEMATIC trial looked at the effect of pooling triple-site samples into one container for a single analysis. Samples were taken from throat and rectum for each individual. Plus, in women, from the vagina; and in men who have sex with men, from the urine. Self-taken samples were pooled (3 per person); swabs taken by clinicians were analysed in 3 separate tests.
The study found that:
- gonorrhoea was detected equally well by pooled and single swabs, both in women and men who have sex with men (both approaches picked up 98% infections)
- chlamydia was slightly less likely to be picked up in pooled swabs than in three separate tests (3% lower for women; 5% lower for men who have sex with men) and 13 infections were missed.
Although the detection rate for chlamydia was lower with pooled samples, it still picked up more than 90% infections, which is the recommended minimum. The researchers say the reduction in sensitivity for men who have sex with men could be due to urine diluting the sample.
In further research, the authors found that most participants (83% men who have sex with men; 77% women) strongly agreed or agreed that they felt confident taking their own swabs. People could take their own swabs in a clinic or at home using postal kits, which many prefer. This also saves time for clinicians.
Why is this important?
The SYSTEMATIC trial found that many infections are missed by the current single-site test. The researchers would like triple-site, pooled samples to be offered to all women and men who have sex with men. This would vastly reduce the number of missed infections.
Pooled samples could introduce significant cost-savings. This matters because, even in high-income countries, publicly-funded health systems struggle to fund individually-tested triple-site swabs. This research demonstrates that sexual health services can save money by pooling triple-site samples from men who have sex with men while introducing routine triple-site testing for all women.
Research from the SYSTEMATIC study shows that the sampling could be done either by a clinician or as a self-test. This would not make a difference to the accuracy of the test. People may be less embarrassed if they can take their own swabs, and it frees up clinicians’ time. Postal kits allow people to take their own swabs at home, which may improve uptake of testing. Plus, self-taken swabs are cheaper than clinician-taken swabs if overseen by a healthcare assistant or performed at home.
What’s next?
Since the trial, the authors have surveyed men who have sex with men to ask how they felt about accepting more missed chlamydia infections at large cost savings to the NHS. They found that most (more than 90%) would be happy with a test that detected 97% infections.
The current test does not quite reach that threshold. SYSTEMATIC researchers are now exploring different pooling techniques, which could increase the detection of chlamydia in men who have sex with men. The research team plans to use a smaller volume of urine, plus a swab of the urethra entrance, to avoid dilution of the sample.
Some clinics have already introduced pooled triple-site samples taken by the individual. Advocacy groups may campaign for wider use of this approach.
You may be interested to read
This summary is based on: Wilson JD, and others. Swab-yourself trial with economic monitoring and testing for infections collectively (SYSTEMATIC): Part 2. A diagnostic accuracy, and cost-effectiveness, study comparing rectal, pharyngeal and urogenital samples analysed individually, versus as a pooled specimen, for the diagnosis of gonorrhoea and chlamydia. Clinical Infectious Diseases 2020;73:9
Sexual health information from the NHS.
SXT: a digital service to signpost patients to their nearest, most appropriate healthcare provider.
The earlier paper from the SYSTEMATIC study: Wilson JD, and others. Swab-yourself trial with economic monitoring and testing for infections collectively (SYSTEMATIC): Part 1. A diagnostic accuracy, and cost-effectiveness, study comparing clinician-taken versus self-taken rectal and pharyngeal samples for the diagnosis of gonorrhoea and chlamydia. Clinical Infectious Diseases 2020;73:9
A poster presentation on extragenital sampling for chlamydia and gonorrhoea: Wallace H, and others. Self-taken extragenital sampling – what do women and MSM think? Feedback from a self-swab and clinician swab trial. Sex Transmitted Infections 2016;92:A61
A recent study evaluating a new rapid sexual health testing, diagnosis and treatment service: Lorenc A, and others. What can be learnt from a qualitative evaluation of implementing a rapid sexual health testing, diagnosis and treatment service? BMJ Open 2021;11:e050109
Funding: This research was funded by the NIHR’s Research for Patient Benefit Programme.
Conflicts of Interest: The study authors declare no conflicts of interest.
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