• CHLAMYDIA TRACHOMATIS
• POLICY
• CONTROL PROGRAMS

In 2009, the European Centre for Disease Prevention and Control (ECDC) published guidance on chlamydia (Chlamydia trachomatis) control in Europe.1 In it we recommended that EU/EEA member states ensure the provision of basic resources and systems (for diagnosis, case and partner management) before embarking on any expanded screening programme. This guidance was based on evidence first that there was a huge variation in availability of clinical services for chlamydia across member states, and second that the evidence for population level programmes was missing.1 ,2 This month ECDC has released updated guidance that we developed with the support of ECDC experts following a programme of work to update the evidence, including an extensive review of the epidemiology and natural history of chlamydia and the clinical and cost-effectiveness of screening programmes.3 The team also repeated the survey of member states, and assessed the impact of the original guidance.4 ,5

The survey showed that more countries had established essential diagnostic and management facilities and guidelines;6 it was hard to attribute this directly to the 2009 guidance although some countries cited its use in advocacy.

So what has changed in the revised guidance?

First, it repeats the recommendation that member states have a national strategy or plan for the control of chlamydia and other sexually transmitted infections. There is a stronger emphasis on the need for primary prevention interventions for at-risk individuals and groups which appears lacking in some areas, and a repeat of the need for evidence-based guidelines for case management and partner notification, a robust system for the surveillance of diagnosed infections and an evaluation plan for the strategy.

While none of this sounds controversial, it is worth noting that the evidence base underpinning these recommendations is patchy at best. Expert opinion supports the provision of primary prevention interventions as there is currently a lack of evidence on the effectiveness of these interventions to prevent infection, but it was considered unlikely that they would cause harm.7 Recommending surveillance is common sense and fundamental to meaningful evaluation and resource allocation.

The guidance goes on to provide clearer recommendations on who should be offered a chlamydia test. We start by making a distinction between ‘clinically-indicated’ testing in individuals with symptoms or risk factors for the acquisition of chlamydia identified during a healthcare consultation and ‘asymptomatic testing’ of sexually active people with no specific risk factor beyond their age.

In this schema, asymptomatic testing includes opportunistic testing and screening. England is the only country that currently has a screening programme for chlamydia offered to young adults from the general population. Many other settings with similar testing rates instead offer opportunistic testing. The difference between these two approaches is not the proportion of the population who are tested, but how the target population is identified and offered a test and how the system is evaluated.

Testing asymptomatic young women (under 25 years of age) is supported by a meta-analysis of randomised controlled trials (RCT) that demonstrates that offering a test reduces the risk of pelvic inflammatory disease at 1 year by 36% (RR: 0.64, 95% CI: 0.45 to 0.90).3 But we do not know the impact of testing in men, the potential harms from the intervention or the impact on reproductive complications in women (ectopic pregnancy and infertility). There is currently no evidence that asymptomatic testing (of any design) can reduce the prevalence of infection at the population level. Therefore, the guidance recommends that widespread opportunistic testing or a screening programme is only implemented if resources are available and suitable monitoring and evaluation is in place. Unfortunately, the evidence base does not allow us to comment on the relative performance of the two approaches to widespread testing of asymptomatic individuals (in terms of impact on chlamydia prevalence or the incidence of post-infectious complications).

Chlamydia testing in an antenatal setting to prevent adverse pregnancy outcomes is commonly undertaken but the guidance recommends that it should be performed in the context of research as there are currently no RCTs of this intervention.

We were unable to recommend indicators for monitoring the performance of asymptomatic testing because the optimal interval between tests is unknown and there are no RCTs that report the level of annual screening required to reduce chlamydia prevalence—if such a level exists.

ECDC guidance on chlamydia control seeks to provide support for decisions around the provision of population-level chlamydia control. But there are—at present—more questions than answers in the evidence base. Before it is time to refresh this guidance, we call on the research community to strengthen our knowledge of the natural history of infection and the impact of interventions at the population level. If we are fortunate enough to see another RCT of chlamydia screening programmes, we suggest that it also explores the potential adverse consequences of the intervention. There is also a specific need for a trial of chlamydia screening in pregnancy.