Clinical Review - Chlamydia

Contributed by Dr Gary Brook, clinical lead in GUM/HIV services, North West London Hospitals Trust, Central Middlesex Hospital

Reiter's disease may be caused by C trachomatis in either sex

Section 1 Genital chlamydia infection
Genital chlamydia infection is caused by the sexually transmitted bacterium Chlamydia trachomatis, serovars D-K. Other C trachomatis strains also cause eye infection (trachoma, serovars A-C) and the genital ulcerative STI lymphogranuloma venereum (serovars L 1-3).

Pelvic inflammation
Infection with chlamydia is the most common cause of pelvic inflammatory disease (PID), ectopic pregnancy and secondary infertility in women in the UK and most of the rest of the world.1-3

These are complications with severe psychological and physical consequences, and it is estimated that the NHS spends as much as £100 million a year treating them.4

In addition, chlamydia causes urethritis, epididymo-orchitis and circinate balanitis in men, cervicitis in women and sexually acquired reactive arthritis and Reiter's disease in either sex.

Asymptomatic infection
One of the reasons C trachomatis spreads through the population is that most infected people are asymptomatic - probably 90 per cent of women and 50 per cent of men.

In addition, this infection is long-lasting, so people who are serially monogamous in their relationships are still at risk. The infection will survive months or even years, spanning relatively long intervals between any changes of partner.

Despite being asymptomatic, the complications of tubal infertility and ectopic pregnancy may still develop in women as a result of chronic low-grade inflammation.1-3

The exact numbers of people infected in the UK are unknown, although population screenings have consistently found a high prevalence in asymptomatic sexually active men and women below 25 years of age.

This varies from about 8 per cent of women seen in primary care to 10-11 per cent of women attending youth and sexual health services (see box).5,6 This high prevalence was recognised as a major public health problem by the DoH 10 years ago, resulting in the National Chlamydia Screening Programme (NCSP) in England.6

Prevalence of chlamydia
Proportion of 15-24 year olds attending national screening
Positive test
Educational settings
General practice attendees
Abortion services
Community contraceptive services
Youth services
Sexual health services
8.7 per cent
4 per cent
8 per cent
9 per cent
10 per cent
10 per cent
11 per cent

Section 2 National screening programme
The NCSP was introduced in 2003, based on data from the US and Sweden and mathematical models suggesting that large-scale population screening would reduce the prevalence of chlamydia.6,7

It is also based on strong evidence that treating identified cases will reduce incidence of PID.8 The evidence that this also translates into reduced rates of infertility and ectopic pregnancy is less robust.9

Screening in the NCSP takes place in a variety of settings, including general practices, pharmacies, community contraceptive clinics, termination of pregnancy services and non-healthcare settings, such as youth clubs and colleges.

It is open to all men and women aged 15-24 years who attend these settings for any reason (opportunistic testing) and normally involves a simple form and a urine sample or self-taken vaginal swab.

All participants are informed of the result, often by text message, and those with a positive result are invited for treatment at the NCSP office, the service at which the specimen was taken or the local GUM clinic.

An important part of this service is that patients are informed of the value of screening for other STIs, the need to screen and treat partners and the efficacy of safer sex.

Local targets
Since 2007 it has been a requirement for all PCTs in England to have a local screening programme with the explicit target of screening 17 per cent of all people aged 15-24 years.4 More than 700,000 people have been screened since 2003, with 330,000 screened in 2007 alone.

However, this means that on average, only 4.9 per cent of the target group are currently being tested annually, and 8.7 per cent of these test positive.4 Testing is also performed in GUM clinics, where approximately 1.1 million tests are performed and 125,000 cases diagnosed.

Opportunities to screen for other STIs in the NCSP are being assessed. Gonorrhoea is common in certain parts of the UK, especially inner cities, so some programmes are also performing a gonorrhoea test on the same urine or swab sample.4

This strategy can only be effective in high-prevalence areas, because in low-prevalence areas false-positive tests are a problem, owing to the specificity of the gonorrhoea urine test.4

Scotland, Wales and Northern Ireland do not have national screening programmes in place for gonorrhoea.

Section 3 Diagnosing chlamydia in primary care
Primary care practitioners in England may be involved in the NCSP. However, chlamydia is frequently diagnosed in people outside the 15-24 years age group. Risk factors (see box) include a partner change in the past 12 months, and requests for termination of pregnancy and/or emergency contraception.4,10

It is also important to screen women before insertion of an IUD because insertion can cause untreated chlamydia to progress to PID.

In areas where the NCSP does not operate, primary care practitioners should recognise the benefits of chlamydia screening in all age groups and situations.

In the past, the chlamydia test had to be done on a cervical swab in women or a urethral swab in men. This made male testing very difficult and testing of women was largely confined to those needing a vaginal speculum examination for other reasons.

Modern tests are based on nucleic acid amplification tests (NAAT) and the sensitivity when used with first-pass urine samples and self-taken vaginal swabs is similar to that of cervical swabs. Many hospital laboratories offer the chlamydia NAAT, although for many GPs, the less sensitive enzyme immunoassay is still the only test available.

Where NAATs are available, a chlamydia screen can be ordered for anybody by obtaining a urine sample, although a special sample container must be obtained from the laboratory.

  • Age under 25 years.
  • New partner in the past 12 months.
  • Inconsistent/no condom use.
  • Requesting emergency contraception.
  • Requesting termination of pregnancy.
  • Past history of STI.

Section 4 Prevention and treatment
Screening for chlamydia and treating identified cases will reduce onward transmission to new partners.10 Identification and treatment of recent partners of patients will further reduce infection.10

Partner tracing
This is one area where GPs may find some difficulty. On the one hand, it has been shown that partner notification of patients diagnosed with STIs can be effectively performed by practice nurses, after training.11

On the other hand, research has shown that many GPs do not see partner notification as part of their role,12 especially if the partner is not their patient.

However, if the partner is not treated, the primary case will be reinfected once sex resumes.10 It is therefore incumbent on GPs to ensure that, if they are not going to initiate partner notification, they send the index patient to the local GUM clinic, where health advisers will perform this task.

Advice on safe sex
Many patients are unaware of the risks of chlamydia and other STIs and do not realise that regular and correct use of condoms is an effective way of reducing the transmission of chlamydia.

Other strategies to prevent STIs that can be discussed with patients are negotiation skills about what sex, including abstinence, is best for them. In people embarking on monogamous relationships, both may attend for an STI screen before commencing unprotected sex.

Although this discussion is focused on chlamydia, an important fact is that people with one STI are more likely to have a second.10 Therefore, all patients diagnosed with chlamydia should be given the information required to have a full STI check-up, such as at the local sexual health clinic.

Treatment strategies
Chlamydia will respond to several antibiotics, although azithromycin 1g as a single dose and doxycycline 100mg twice daily for one week are the most effective and common regimens.10

Ofloxacin 400mg once daily for one week or erythromycin for two weeks at a dosage of 250mg four times daily or 500mg twice daily are also effective, but with a slightly lower efficacy (<95 per cent); they therefore need to be followed by a test of cure five weeks after completion of treatment.10

Amoxicillin has quite a high failure rate and is not recommended unless other treatments are contraindicated.

Doxycycline and ofloxacin are contraindicated in pregnancy and although azithromycin is often used,10 it is not licensed in this situation.

Complicated chlamydia infection, such as PID or epididymo-orchitis, requires two weeks of antibiotic therapy.

Chlamydia is a common and easy to treat STI. However, if we are to make inroads into reducing the incidence of chlamydia and its complications, screening in primary care settings must be substantially increased.

1. Paavonen J, Eggert-Kruse W. Chlamydia trachomatis: impact on human reproduction. Hum Reprod Update 1999; 5: 433-47.

2. Simms I, Stephenson JM. Pelvic inflammatory disease epidemiology: what do we know and what do we need to know? Sex Transm Infect 2000; 76: 80-7.

3. Hillis SD, Joesoef R, Marchbanks PA et al. Delayed care of pelvic inflammatory disease as a risk factor for impaired fertility. Am J Obstet Gynecol 1993; 168: 1503-9.

4. DoH. National Chlamydia Screening Programme (NCSP) in England (second edition). DoH, London, July 2004.

5. Pimenta JM, Catchpole M, Rogers PA et al. Opportunistic screening for genital chlamydial infection. 2: prevalence among healthcare attenders, outcome, and evaluation of positive cases. Sex Transm Infect 2003; 79: 22-7.

6. National Chlamydia Screening Programme.

7. Adams EJ, LaMontagne DS, Johnston AR et al. Modelling the healthcare costs of an opportunistic chlamydia screening programme. Sex Transm Infect 2004; 80: 363-70.

8. Scholes D, Stergachis A, Heidrich FE et al. Prevention of pelvic inflammatory disease by screening for cervical chlamydial infection. N Engl J Med 1996; 334: 1362-6.

9. Low N, Egger M, Sterne JA et al. Incidence of severe reproductive tract complications associated with diagnosed genital chlamydial infection. Sex Transm Inf 2006; 82: 212-18.

10. Horner P, Boag F. 2006 UK National Guideline for the Management of Genital Tract Infection with Chlamydia trachomatis. (accessed 13 January 2009)

11. Low N, McCarthy A, Roberts TE et al. Partner notification of chlamydia infection in primary care: randomised controlled trial and analysis of resource use. BMJ 2006; 332: 14-19.

12. Cassell JA, Brook MG, Slack R et al. Partner notification in primary care. Sex Trans Infect 2003; 79: 264-5.

Further resources

1. British Association for Sexual Health and HIV management guidelines for all STIs

2. Index of Sexual Health clinics in the UK

3. National Chlamydia Screening Programme

4. Sexual Health Direct - FPA patient helpline

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