UK sexual health conference debates move to less frequent STI screening

One of the last sessions of the recent joint conference of the British HIV Association (BHIVA) and the British Association of Sexual Health and HIV (BASHH) covered BASHH’s most recent clinical guidelines.

Professor Margaret Kingston, the Chair of BASHH’s Clinical Effectiveness Group, introducing the session, told delegates the session would not, this year, be devoted to detailed updates of STI treatment guidelines. Instead, it would focus on one proposed change – whether to carry on screening gay and bisexual men and trans/non-binary people who have sex with men (GBMSM) for chlamydia and gonorrhoea every three months, or to change to screening every six months.

‘Screening’ means testing people who don’t have symptoms. Anybody with symptoms of a possible STI would still be tested.

The significance of changing the recommendation on screening and the range of opinions about it justified making it the sole topic of discussion, Kingston said. Dr Helen Fifer of the UK Health Security Agency (UKHSA) began by reviewing the advantages and disadvantages of moving to less frequent screening.

Advantages of less frequent screening

Firstly, it’s unlikely that less frequent screening would significantly damage people’s health.

Around four in five chlamydia infections are asymptomatic. A similar proportion of rectal and pharyngeal (throat) infections of gonorrhoea are asymptomatic too, and these are the most common sites of gonorrhoea in gay men. Urethral and endocervical gonorrhoea is also often asymptomatic in women (around half of cases) but less so in men (around one in ten).

It is not known how infectious asymptomatic chlamydia and gonorrhoea are, though it has been suggested that PCR tests that detect these organisms’ RNA are “too sensitive” and may detect residual RNA rather than infectious bacteria.

In addition, chlamydia and gonorrhoea sometimes self-resolve – in other words go away by themselves. This is an under-researched area, and studies have looked at widely different time frames to define spontaneous clearance.

UKHSA’s 2024 report found that 24% of chlamydia infections had cleared spontaneously within 27 days. Another study, using a much longer time frame, found that nearly 80% of infections had cleared spontaneously within a year.

Similarly, for gonorrhoea, one study found that 21% of infections had cleared within 10 days and another that 77% had cleared within 70 days (2.5 months).

Secondly, more screening leads to more infections being treated, and there is the issue that overuse of antibiotics can lead to drug resistance. The Chlamydia trachomatis organism finds it difficult to develop resistance but for Neisseria gonorrhoeae it is easy. Starting with antibiotic treatment in the 1940s, gonorrhoea has become successively resistant to five different classes of antibiotic. It is currently treated with ceftriaxone, a drug in the sixth class, but cases of ceftriaxone-resistant gonorrhoea, though rare, are becoming more frequent. Evidence from studies of doxyPEP – using the drug doxycycline to prevent bacterial STIs – show that resistance in gonorrhoea to drugs of its class rises when doxyPEP starts being used widely.

Thirdly, antibiotics are powerful drugs and are not without side effects, especially in terms of disrupting the natural ‘biome’ or population of often beneficial bacteria that people naturally carry, especially in the gut.

Finally, frequent screening is costly – to health systems in staffing and laboratory capacity,  and to patients in time and anxiety. Reduced testing enables resources to be invested in issues with higher personal and public health consequences than symptomless STIs.

In other words, testing for STIs every three months and treating all diagnosed might be unnecessary. There are arguments for maintaining three-monthly screening, however.

Disadvantages of less frequent testing

Firstly, we do not know how many onward transmissions may be due to asymptomatic infections. If screening was every six months, someone who acquires an STI a month after testing has five more months – rather than two months – during which they might possibly be infectious, even with no symptoms. This is an area that needs more research.

Secondly, as many as one in six cisgender women may develop pelvic inflammatory disease (PID), a major cause of infertility, as a result of untreated chlamydia or gonorrhoea infections. While other serious health consequences of these STIs are uncommon, especially in men and people assigned male at birth, untreated gonorrhoea can occasionally result in a disseminated infection – a severe complication in which the infection spreads through the bloodstream and can cause inflamed joints and skin lesions.

There is also lymphogranuloma venereum (LGV), a painful condition caused by particular strains of chlamydia and usually seen in gay men. Only a minority of LGV infections are asymptomatic, but may cause symptomatic infections if transmitted.

Thirdly, three-monthly screening also usually include tests for syphilis, HIV and hepatitis B and C. Although uncommon, secondary and early latent syphilis can sometimes cause significant morbidity, and detecting HIV as soon as possible results in better clinical outcomes and reduced onward transmission.

Fourthly, six-monthly testing may result in less data about the prevalence, risk and spread of STIs and the ability to monitor the impact of interventions. It also halves the time available for in-person healthcare, including conversations and advice about risk management.

Finally, it would be an unwelcome cultural change for some patients who value regular testing and might feel anxious about carrying an undiagnosed infection.

The evidence

Dr John Saunders, head of programme delivery and service improvement in the UKHSA’s blood-borne viruses research laboratory, reviewed the evidence on three- and six-month screening.

The only randomised controlled trial to test the question was the Belgian GonoScreen study, which was covered in detail by aidsmap here.

This study compared the results of three-monthly screening for chlamydia, gonorrhoea and syphilis and treating all infections, with only treating symptomatic infections – a greater change than what BASHH is proposing. All diagnoses were recorded, but did not inform or treat people who had no symptoms.

The researchers hypothesised that three-monthly treatment was over-diagnosing infections that would not need treatment or even be noticed, and that there would therefore be a lower incidence of all infections in the non-screened (symptomatic) arm.

In fact, they saw more infections (symptomatic and otherwise) in the non-screened arm. This was in part driven by untreated-infections persisting beyond three months and therefore being ‘double counted’ at the next visit (in this study, only 50% of untreated chlamydia had spontaneously cleared by three months). But they certainly did not see fewer infections in the non-screened arm.

Other studies have found that higher screening intensity is associated with higher symptomatic STI incidence, perhaps because symptoms often eventually clear by themselves. Three monthly treatment of all infections is also associated with a slightly greater reduction, over several years, in prevalence (i.e. the number of people who at any one time have an STI).

Studies have also found that more screening is associated with higher rates of antibiotic resistance. Three-monthly screening is also extremely uneconomic. One European cost-effectiveness study found that each quality-adjusted life year (QALY) gained by three-monthly rather than six-monthly testing cost an extra €430,000 – 21 times the usual cost-effectiveness threshold.

Qualitative studies show that people using sexual health services are suspicious of moving to less frequent testing. Three-monthly testing has become a mark of social responsibility and validation, as well as allaying anxiety, for gay and bisexual men and trans people who use PrEP, who fear that if less testing meant more onward transmission, it would increase anti-gay stigma. There is little awareness that asymptomatic STIs are generally harmless or can self-resolve. In addition, people are suspicious of changes in service that appear to be based on cost.

Some physicians also worry about onward transmission and are more influenced by the obligation as doctors to “treat the patient in front of them” than to conserve antimicrobial efficacy. They are also concerned that disrupting the regularity of testing might jeopardise the trusted doctor-patient relationship.

Summarising his findings, Saunders said that though there is “no evidence that frequent screening reduces chlamydia or gonorrhoea incidence”, any change must be “co-designed with communities and clinicians including transparent messaging about risks, benefits and natural clearance.”

Community reaction and evaluation

Dr Benjamin Weil, head of research and community knowledge generation at The Love Tank said that sexual behaviour norms involve ideas about responsible practice, responsible people, and trustworthy partners. They can be spread from the “top down” in health promotion messages, but can also be “bottom up”: he drew on PrEP as an example of how the LGBT+ community embraced a new norm that, in creating feelings of safety and health, also reduced the anxiety and enhanced the pleasure of sex.

A move to six-monthly testing would therefore need to be handled carefully for the LGBT+ community to feel they had agency over such a change: “Engagement with communities is required from the outset in co-creating norms and values,” he said, emphasising that values of safety and responsibility would need to be preserved.

Ceri Evans, Senior Health Adviser at the 10 Hammersmith Broadway sexual health clinic in west London, said that one size might not fit all. Three-month testing might need to be preserved for people with specific vulnerabilities, people under the age of 18, people selling sex, and those not using PrEP or using chems problematically – or whose partners might be vulnerable, such as people also having sex with cisgender women.

A halfway house might be to introduce three-monthly testing for HIV and syphilis with postal kits, Evans said. But she was also concerned that less frequent testing risked losing the opportunity to have conversations about risk reduction, safeguarding, alcohol and drug use and similar issues.

Audience questions and comments revealed a divergence of opinions, ranging from considerable concern about onward infection to full agreement that three-monthly testing consumed resources that might be better spent elsewhere. Community representatives said that any move towards three-monthly testing needed to be accompanied by clear and accurate information about the frequency and health consequences of asymptomatic STIs, infectiousness and spontaneous clearance – information that doctors may not have communicated well in the past due to worry that it might discourage testing.