Screening for Chlamydia trachomatis

The case for screening is made, but much detail remains to be worked out

News p 1479

This month the chief medical officer of England published the report of an expert advisory group on Chlamydia trachomatis, which highlighted the need for immediate action to reduce the prevalence of chlamydia infection and the morbidity associated with it.1 Chlamydia is the most prevalent, treatable sexually transmitted infection in the United Kingdom and has serious sequelae, including pelvic inflammatory disease, infertility, ectopic pregnancy, and neonatal infections. All these conditions, except for infertility, have been shown to be preventable if chlamydia trachomatis is treated in its asymptomatic phase. The expert group is proposing an education campaign to increase awareness of chlamydia infection coupled with opportunistic screening of asymptomatic sexually active young women.

The advisory group's main recommendations are to offer testing to all men and women with symptoms of infection, all attenders at genitourinary medicine clinics, and women seeking terminations of pregnancy and to screen opportunistically sexually active women aged under 25 and those over 25 with new sexual partners in the previous 12 months. The group considers that screening for chlamdyia meets the Wilson and Junger criteria for a workable screening programme: C trachomatis infection is an important problem, asymptomatic infection can be accurately diagnosed, and effective treatment exists. However, having established the case for screening, the group recommends research to design and implement an appropriate screening programme and outlines a research programme amounting to £3.2m. This would address the cost benefit of different approaches, the need for public and professional education, the acceptability of screening, which tests, specimens, and treatments to use, and the most effective way of tracing partners. The government has responded by announcing two pilot projects to start this year as part of a general feasibility study.

The recommendations to target all sexually active women aged under 25, those undergoing terminations of pregnancy, and others at high risk (such as women with a new sexual partner in the previous 12 months) are based on data collected by several centres, but none are sufficient to give a true national picture. In the United States, in family planning settings, screening the under-25s missed 20% of cases of chlamydia infection while screening the under-30s missed only 7%.2 Data collected from genitourinary medicine clinics in England in 1996 show that 25% of uncomplicated cases of chlamydial infection in women occur in those aged 25-34.

The advisory group has concluded that general practitioners and family planning clinics are best placed to carry out opportunistic screening as, between them, they will see over 95% of their registered patients over a three year period. The group suggests that screening should be offered by general practitioners during routine consultations and that this would be “unlikely to significantly increase the costs associated with treatment.” When community midwives offered HIV testing to all at booking clinics, however, it added an average of 7 minutes per consultation (range 2-15).3 General practitioners and and family planning clinics will need additional time and resources to carry out this programme, and the pilot projects need to address this issue.

Another issue that is likely to emerge is that of reporting by general practitioners of sexually transmitted disease on health reports for insurance purposes. Prior consultation with the Association of British Insurers could prevent recurrence of the types of problems encountered in HIV testing.4

For patients with positive results (and the best specimen to take and test to perform have yet to be determined) the advisory group advises referral to genitourinary medicine clinics for a full screen for sexually transmitted diseases and contact tracing. The group recognises, however, that some patients may not want to attend such a clinic. Contact tracing for chlamydia, which currently does not receive high priority in genitourinary medicine clinics and is ineffective elsewhere,5 needs much improvement before a screening programme will be successful.

The role of chlamydia in infertility is well documented: the disease may be implicated in as much as 50% of cases. Many cases of infertility occur in the absence of clinical pelvic inflammatory disease, and when this disease process occurs is unknown. A reduction of the incidence of chlamydia infection in the community may therefore produce a corresponding fall in the related incidence of infertility.

The role of health education needs to be emphasised to ensure the efficacy of any screening programme. As schools can provide education about sexually transmitted disease only with parental consent, the burden of providing such education would presumably fall to general practitioners and family planning clinics. The research projects could usefully address whether the severe consequences of untreated chlamydia infection warrant an active government role in providing sexual health education. Indeed, final judgment on the value of the proposed screening programme—and whether Britain can achieve the reductions in morbidity that have been seen in, for example, Sweden6—must await the promised pilots.