HIV/Sexually Transmitted Infections (STIs) |
Published on: 30 October 2009 |
Genital chlamydial infection in the United Kingdom: 1999-2008
Genital chlamydial infection (Chlamydia trachomatis) is the most common bacterial sexually transmitted infection (STI) seen in the UK. Chlamydia is often asymptomatic, with approximately 70% of infected females and up to 50% of infected males thought to be asymptomatic [1]. Complications of chlamydia infection include pelvic inflammatory disease (PID), tubal damage (which can lead to infertility and ectopic pregnancy), chronic pelvic pain, and sexually acquired reactive arthritis [1]. Once diagnosed, infections can usually be successfully treated with antibiotics.
To gain a more accurate view of chlamydial infections diagnosed in the UK, the data presented here includes information from all settings where chlamydia diagnoses are made, including primary care. In contrast to previous reports which focused on chlamydia diagnoses made by genitourinary medicine (GUM) clinics, the data are now compiled from a number of different sources: national mandatory reporting from GUM clinics, voluntary reporting of chlamydia diagnoses by laboratories and, in England, reports from the National Chlamydia Screening Programme (NCSP) [2].
Trends in diagnoses
In 2008, there were an estimated 200,959 diagnoses of genital chlamydia infection made across all clinical settings in the UK [2]. Over the past 10 years, diagnoses have risen steadily in men and women across all age groups but the rise was most pronounced in women aged under 25 years and men aged 20-24 (figures 1a and 1b). Overall, numbers of diagnoses were much lower in men than in women.
Figure 1a. Number of genital chlamydia diagnoses by sex and age group, and number of laboratories using nucleic acid amplification tests (NAATs): 1999-2008 (males)
Figure 1b. Number of genital chlamydia diagnoses by sex and age group, and number of laboratories using nucleic acid amplification tests (NAATs): 1999-2008 (females)
Although some of the rise in diagnoses may be due to changes in sexual behaviour resulting in more people becoming infected, the use of highly sensitive diagnostic tests (Nucleic Acid Amplification Tests, NAATs) have also contributed to the rise in diagnoses (figures 1a and 1b), as well as increased rates of testing across the UK [3]. In England, the National Chlamydia Screening Programme was established in 2003 to provide opportunistic screening to asymptomatic young people under 25 years in settings outside of GUM clinics [4]. Roll-out of the programme over the past six years has resulted in a substantial rise in the numbers of people tested (figure 2) [5].
Figure 2. Number of tests among 15-24 year old males and females screened within the NCSP, England: 2003-2008
The highest rates of chlamydia diagnosis are seen in 16-19 year old women and 20-24 year old men (figure 3). Guidelines for chlamydia screening and testing vary across the UK, but most target those aged under 25 as they experience the highest rates of infection. In England, opportunistic screening is proactively offered through the NCSP, mainly targeting those aged 15-24 [6], and a similar approach is planned in Northern Ireland [7]. There is no formal screening programme in place in other parts of the UK, but opportunistic chlamydia testing is recommended for those with highest prevalence, including those aged under 25 years, in primary care and community settings [8,9].
Figure 3. Rates of genital chlamydia diagnoses by sex and age group in the UK: 2008
As a result, across the UK the proportion of chlamydia diagnoses made outside the GUM clinic setting has been rising steadily and is substantial [5]. In 2008, in England, 52% (70,809/137,482) of all chlamydia diagnoses in those aged under 25 years were made in GUM clinics, 35% (48,425/137,482) were made through the NCSP, and 13% (18,248/137,482) were made in non-GUM clinic settings not reporting to the NCSP (figure 4). In Scotland, around half of chlamydia diagnoses (of all ages) in 2006 were made outside GUM clinic settings [10].
Figure 4. Number of chlamydia diagnoses by source of report for ages 15-24, England: 2008
The National Chlamydia Screening Programme in England
In 2008, the NCSP performed 579,434 screens for chlamydia on those aged 15-24 in England, a substantial increase which is associated with the expansion of the programme since its launch in 2003 (figure 2). Testing rates were considerably higher in women than in men (figure 2). In 2008, positivity (the number of positive tests as a percentage of the total number of tests done) was 7.7% among men and 8.7% among women, highlighting the high rates of asymptomatic infection among young adults.
The majority (65%) of those screened by the NCSP in 2008 were white (figure 5). Overall chlamydia positivity was 8.4% (95% confidence interval 8.3%-8.4%) and was highest in those of black (10.8%, 95% CI 10.5%-11.2%) and mixed (10.7%, 95% CI 10.3%-11.2%) ethnicity, and lowest in Asians (3.4%, 95% CI 3.1%-3.7%).
Figure 5. Positivity by ethnicity in 15-24 year olds screened for NCSP, England: 2008
Overall, 35% of those screened through the NCSP in 2008 reported two or more partners in the previous 12 months. Chlamydia positivity was higher in those reporting two or more partners in the previous year (11.1%) than in those reporting fewer partners (6.5%). Similarly, 10.7% of those screened who reported a new sexual partner in the previous three months were diagnosed with chlamydia compared with 7.1% of those reporting no new partners.
Key messages- Chlamydia is a common infection in young adults in the UK .
- There were over 200,000 chlamydia diagnoses in the UK in 2008.
- The recent rapid rise in diagnoses is associated with more people being testing and the use of more sensitive diagnostic tests; changes in sexual behavioural may also have played a role.
- Many chlamydial infections are asymptomatic. Screening can help ensure that asymptomatic infections are identified and treated, thereby reducing the likelihood of transmission and the development of complications.
References
1. British Association for Sexual Health and HIV (BASHH). 2006 UK National Guideline for the Management of Genital Tract Infection with Chlamydia trachomatis. London: BASHH, 2006. Available at: http://www.bashh.org/documents/61/61.pdf.
2. Health Protection Agency. Chlamydia diagnoses reported in the UK and England: 2008. London: HPA, 2008. Available at: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1247816548177.
3. Health Protection Agency. Testing Times – HIV and other sexually transmitted infections in the United Kingdom: 2007. London: HPA, 2007. Available at: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1203496897276.
4. Department of Health. The national strategy for sexual health and HIV implementation action plan. London: Department of Health, 2002.
Available at: http://www.dh.gov.uk/en/Publicationsandstatistics/
Publications/PublicationsPolicyAndGuidance/DH_4006374.
5. National Chlamydia Screening Programme. NCSP National 2009/10 Data. London: NCSP, 2009. Available at: http://www.chlamydiascreening.nhs.uk/ps/assets/pdfs/data/sha_presentations09/
National%20Q1%202009-10.pdf.
6. National Chlamydia Screening Programme. NCSP Professional Site. London: NCSP, 2009. Available at: http://www.chlamydiascreening.nhs.uk/ps/index.html.
7. McBridge M. Letter to HSS board members. 4 July 2008. Belfast: DHSSPSNI. Available at: http://www.dhsspsni.gov.uk/hss-md-23-2008.pdf.
8. Scottish Intercollegiate Guidelines Network. SIGN 109: Management of genital Chlamydia trachomatis infection. London: SIGN, 2009. Available at: http://www.sign.ac.uk/guidelines/fulltext/109/index.html.
9. Communicable Disease Surveillance Centre. HIV and STI Trends in Wales. Cardiff: CDSC. Available at: http://www2.nphs.wales.nhs.uk:8080
/CommunitySurveillanceDocs.nsf/3dc04669c9e1eaa880257062003b246b/ccdcec5f6436c32080
257555004fcd04/$FILE/HIV%20and%20STI%20trends%20in%20Wales%202008%20Version%201a.pdf.
10. Information Services Division Scotland. Sexually transmitted infections and other sexual health information for Scotland. Edinburgh: Information Services Division Scotland, 2007. Available at: http://www.isdscotland.org/isd/servlet/FileBuffer?namedFile=sexual-health-2007.pdf&pContentDispositionType=attachment [8.5 MB PDF].
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