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Chlamydia screening
Executive Editor, InnovAiT
E-mail: chantal.simon{at}oxfordjournals.org
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Abstract |
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TOP
Abstract
The GP contract and...Chlamydia is the most common sexually transmitted infection (STI) in the UK. It is asymptomatic in 70% of infected women and 50% of infected men and so often goes undiagnosed. Between 2000 and 2004, the rate of new diagnoses of chlamydia among people who attended Genito-urinary medicine clinics greatly increased from 116 to 175/100 000 (Fig. 1), with the largest increases in chlamydia rates occurring in the under 16 age group. However, the highest rates of chlamydia infection are seen in females aged between 16 and 19 years (1339/100 000) and males aged 20–24 years (1034/100 000). The National Chlamydia Screening Programme (NCSP) in England was established in 2003 with the objective of controlling chlamydia through the early detection and treatment of asymptomatic infection, thus preventing the development of sequelae and reducing onward disease transmission. Similar programmes are underway in the rest of the UK.
Chlamydia screening is covered within the GP Curriculum within two curriculum statements: Statement 5—Healthy people and Statement 11—Sexual health. Statement 5 requires GPs to be able to demonstrate an understanding of the epidemiology of problems presenting in primary care and the benefits and risks of screening programmes. To adopt a person-centred approach, the GP should be able to interpret evidence about a screening programme and decide whether it is worthwhile—for individuals or groups—and promote health through a health promotion or disease prevention programme, such as the NCSP. Statement 11 requires GPs to have knowledge of National screening programmes with relevance to sexual health. This includes the NCSP. In addition GPs must be able to:
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Sequelae of chlamydia infection |
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In the absence of treatment, 10–40% of women with chlamydia infection will develop pelvic inflammatory disease (PID) with a significant proportion of these cases being asymptomatic or having mild or atypical symptoms. It is estimated that 50% of cases of PID are caused by genital chlamydial infection. PID can result in:
- chronic pelvic pain—20% of women treated for PID
- tubal factor infertility—20% of women treated for PID will become infertile due to tubal damage and
- ectopic pregnancy—occurs in 1% of pregnancies and is the most common cause of maternal death in the first trimester, accounting for 9% of maternal deaths; 43% of ectopic pregnancies are caused by genital chlamydial infection
The risk of developing PID increases with each recurrence of Chlamydia trachomatis infection, as does the risk of reproductive sequelae.
Other complications include Fitz-Hugh–Curtis syndrome, a rare perihepatitis causing right upper quadrant pain; bartholinitis; transmission to neonates (neonatal conjunctivitis and pneumonia); epididymo-orchitis; adult conjunctivitis and sexually acquired reactive arthritis or Reiter's syndrome (more common in men). It is estimated that complications of chlamydia infection cost at least £100 million annually in the UK.
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The establishment of a National Screening Programme |
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The World Health Organization recommends that screening should only be introduced to a target population if the Wilson–Jungner criteria (Box 1) are met. In 1998, the Chief Medical Officer's Expert Advisory Group on Chlamydia trachomatis considered the evidence base associated with screening for genital chlamydial infection. This group concluded that chlamydia screening met the criteria for public health intervention and recommended the establishment of a screening programme.
Box 1. Wilson–Jungner criteria for introduction of a screening programme
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Screening programmes had already been established in other countries. The US piloted a regional chlamydia screening programme, the STI-related Infertility Prevention Project, in 1988 and demonstrated a 65% decline in infection in family planning clinic attenders in the first 8 years of screening. Sweden also saw similar declines after implementing widespread screening. Two randomized controlled trials, in the United States and Denmark, halved the incidence of PID cases after 12 months of screening for chlamydia among asymptomatic women. Furthermore, the majority of health economic valuations demonstrate that chlamydia screening is cost effective.
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Aims of the screening programme |
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The NCSP aims to ensure that young people under 25 years of age are aware of their risk of acquiring chlamydia, its potential reproductive complications and have access to screening, prevention and treatment services. The NCSP aims to control chlamydia by early detection and treatment of asymptomatic infection thus preventing sequelae and by reduction of onward disease transmission.
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Organization of the programme |
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National coordination and management of the chlamydia screening programme is the responsibility of the Health Protection Agency, under contract to the Department of Health, guided by the Project Board and the National Chlamydia Screening Advisory Group. Local management (organization, delivery and monitoring) of chlamydia screening is coordinated within geographically distinct programme areas. These programme areas are managed by a Local Chlamydia Screening Steering Group, chaired by a Programme Lead, through a local chlamydia screening office (CSO)—Fig. 2.
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Availability and eligibility
Screening is offered opportunistically to any sexually active young person under the age of 25. To maximize uptake, a wide variety of community-based venues are used to deliver the screening service (Table 1).
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Young people under the age of 16 may be included if deemed ‘Fraser’ competent. Contacts of screened positives are also included regardless of age. Groups ‘not’ eligible for screening include individuals who:
- have symptoms and request testing for diagnostic reasons
- are unwilling to leave any means of contact to receive their result
- are over the age of 16 but unable to consent to chlamydia screening due to lack of understanding and/or impaired mental capacity or
- are under 16 years of age and not deemed Fraser competent
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The screening test |
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All laboratories providing a testing service for the NCSP must use a Nucleic Acid Amplification Test (NAAT). NAATs not only are the most sensitive and specific tests currently available but also allow the use of non-invasive specimen collection, such as urine and self-taken swabs, which is more acceptable to young people who wish to be screened.
- For women, a self-taken vaginal swab or first-void urine sample is used. Cervical swabs are only employed for screening purposes if a vaginal examination is being undertaken for another reason.
- For men, a first void urine sample is used
Urine samples should only be taken if the young person has not passed urine for at least an hour prior to the test (2 hours for some tests). The first urine passed should be collected in the sample bottle supplied.
Consent
Young people do not need to give written consent to chlamydia screening. For the NCSP, implied consent is assumed if the young person has
- received a copy of the NCSP patient information leaflet (copies can be obtained by emailing: ncspteam{at}hpa.org.uk)
- completed the specimen request form—some parts of which are self-completed and
- provided a sample
Screening interval
Screening is usually offered to sexually active men and women under the age of 25 annually or whenever there is a change in sexual partner. Reinfection is relatively common affecting roughly 1 in 10 of those treated for chlamydia infection within a year. Additional screening may be offered if there has been known or suspected non-compliance with treatment, a failed partner notification or treatment, or if the young person is in a non-monogamous relationship. A minimum of 5 weeks is recommended between tests.
How soon do tests become positive?
There are no data on how soon after sex with a new partner a NAAT for chlamydia may become positive. The NCSP has agreed the following:
- test immediately, then
- repeat the test in 3–5 weeks
If the first test is positive, it may be because the index person already has chlamydia or if the young person is female, the test is picking up chlamydia in her partner's semen. In the latter case, the test may revert to negative after a few days and then, if the woman develops chlamydia, it will change back to being positive, hence the recommendation to repeat the test in 3–5 weeks.
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Results, treatment and contact tracing |
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Results are sent to young people who have been screened whether they are positive or negative. The young person is asked to provide a contact point on the screening request form. Texting is the most costeffective way of communicating test results. Depending on local arrangements, follow-up is undertaken either by the local CSO or by the community health-care organization providing screening.
Negative results
Most young people receiving negative results need no further intervention. However, there is a box about symptoms on the screening request form. Those individuals who tick the box indicating that they have symptoms do require follow-up to ensure appropriate investigation of those symptoms. This usually involves advice to seek full assessment either via general practice, a family planning or young people's clinic, or a genito-urinary medicine clinic.
Positive results
When a chlamydia screening test is reported as positive by the laboratory, the test is repeated on the same sample to confirm the result. Then, the young person is informed. Delivery of follow-up care varies between locations, but in all cases, it involves the taking of a sexual history and safe sex advice. Young people should always be advised to have a full sexual health screen, especially if they have symptoms. This can be done in general practice, a family planning or young people's clinic, or a genito-urinary medicine clinic. However, even if a full sexual health screen is declined, treatment for chlamydia infection should be offered.
Treatment options
The NCSP directions recommend treatment of all young people screening positive for chlamydia infection in line with recommendations of the British Association for Sexual Health and HIV. All medication provided through the NCSP is free of charge to the patient. Currently, all men and non-pregnant women are treated with either doxycycline 100 mg bd for 7 days or azithromycin 1 g as a single, one-off dose. For those unable to take either of these drugs, ofloxacin 200 mg bd (or 400 mg od) for 7 days or erythromycin 500 mg bd for 10–14 days are alternatives. For pregnant women, use erythromycin 500 mg qds for 7 days (or bd for 14 days) or azithromycin 1 g (unlicenced) as a single dose.
Partner notification
Contact tracing is extremely important for the success of the NCSP. The greatest risk of reinfection for the index case is from the current partner. Therefore, it is very important that the current partner is screened and treated.
Young people screening positive for chlamydia are asked about their preferred method of partner notification. Three options are available:
- Patient referral—notifying their own partner
- Provider referral—supplying information so that the screening coordinator or sexual health adviser can arrange for their partner to be informed without disclosing the young person who has screened positive's identity
- Negotiated or contract referral—provider referral is offered if the patient is unsuccessful in notifying their contact or the contact fails to attend a clinic although aware of the infection
Women and asymptomatic men should be asked to contact (or for the contact details of) all sexual partners that they have had in the previous 6 months or their previous partner if they have had no sexual partners in that time period. Men with symptoms of chlamydia infection should be asked to contact (or for the contact details of) all sexual partners from 1 month prior to the onset of symptoms or their previous partner if they have had no sexual partners in that time period.
Partners traced in this way are offered chlamydia testing but this is not mandatory. In all cases, treatment is given, whether or not the contact has been tested for chlamydia, immediately and without waiting for chlamydia test results.
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Test of cure
Test of cure is not recommended as a matter of routine for participants in the NCSP with the exception of young people treated with erythromycin. For these individuals, a repeat test should be considered 5 weeks after the original test date (or 3 weeks after the end of the 14-day course). A test of cure prior to 5 weeks may miss patients with delayed therapeutic reaction to treatment or detect non-viable organisms.
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Statistics from the National Chlamydia Screening Programme |
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The most recent data available from the NCSP are those from June–April 2008. During that time:
- 121 278 screens were performed
- 10 913 tested positive, an overall positivity rate of 11.1%
From the NCSP 2004–05 report:
- 96% of all those who screened positive were treated—the majority (more than 75%) in community settings rather than genito-urinary medicine clinics
- Partner contact rate was 56% and 65% of those partners contacted received confirmed treatment
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Negative effects of screening |
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In many screening programmes, an increase in anxiety levels associated with screening has been observed. There has been very little research done into the psychological effects of chlamydia screening. A recent Health Technology Assessment study (2007) following young people through the screening process showed that anxiety levels went down in the interval between first assessment (prior to the invitation to screening) and final assessment (done once a negative result had been received). The decline in men's anxiety levels occurred when they submitted their samples. Women's anxiety levels only declined once a negative result had been received.
In the same study, participants who received a positive diagnosis reported feeling shocked and the news was a source of considerable distress for some. Specific concerns were the possibility that they might have other STIs and the need to inform current and recent sexual partners of their test result. However, these individuals also recognized the benefits and were, on the whole, glad to have been tested.
One common concern about screening is that being tested for a STI or being treated for an asymptomatic chlamydial infection might be disclosed to insurers and affect insurance premiums. The British Medical Association and the Association of British Insurers have produced guidance for GPs on this issue. Information should not be revealed about whether an applicant for insurance has undertaken tests for STIs, nor should any negative results be revealed. Doctors should also not reveal information about an isolated incident of an STI that has no long-term health implications or even multiple episodes of non-serious STIs, again where there are no long-term health implications.
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Screening in other settings |
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Outside the setting of the NCSP, chlamydia screening using standard laboratory services is also recommended for the following groups:
- Sexual partners of those with proven or suspected chlamydia infection
- All women attending genito-urinary medicine clinics, whatever their age
- All women undergoing termination of pregnancy
- Prior to insertion of an intrauterine device in women considered to be at high risk of STI
- Mothers of infants who have contracted Chlamydial conjunctivitis or Chlamydial pneumonitis
- Semen and egg donors
Key points
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References |
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ABI/BMA. Medical information and insurance (2008) Accessed via www.abi.org.uk/Document_Vault/2008_BMA-ABI_Guidance_FINAL.pdf [date last accessed 16.09.2008].
Adams EJ, Turner KM, Edmunds WJ. The cost effectiveness of opportunistic chlamydia screening in the UK. Sexually Transmitted Infections (2007) 83(4):267–74.
British Association for Sexual Health and HIV (BASHH). UK national guideline for the management of genital tract infection with Chlamydia trachomatis (2006) Accessed via www.bashh.org/documents/61/61.pdf [date last accessed 15.09.2008].
Clinical Knowledge Summaries (CKS). Chlamydia—uncomplicated genital (2006) Accessed via cks.library.nhs.uk/Chlamydia_uncomplicated_genital [date last accessed 15.09.2008].
Department of Health. Annual Report of the National Chlamydia Screening Programme in England (2004/05) Accessed via www.Chlamydiascreening.nhs.uk/ps/assets/pdfs/a-rprt-04_05.pdf [date last accessed 24.10.2008].
Department of Health. Summary and conclusions of CMO's Expert Advisory Group Report on Chlamydia trachomatis (1998) Accessed via www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_4062264.pdf [date last accessed 15.09.2008].
Department of Health. The National Chlamydia Screening Programme in England: core requirements (2008) 4th edition. Accessed via www.Chlamydiascreening.nhs.uk/ps/assets/pdfs/NSCP_CoreReq_4th_edition_latest.pdf [date last accessed 16.09.2008].
Low N, McCarthy A, Macleod J, et al. Epidemiological, social, diagnostic and economic evaluation of population screening for genital chlamydial infection. Health Technology Assessment (2007) 11(8). Accessed via www.hta.ac.uk/fullmono/mon1108.pdf [date last accessed 15.09.2008].
National Chlamydia Screening Programme. Accessed via www.Chlamydiascreening.nhs.uk [date last accessed 15.09.2008].
NICE. Long acting reversible contraception (2005) Accessed via www.nice.org.uk/nicemedia/pdf/CG030fullguideline.pdf [date last accessed 15.09.2008].
RCGP. Curriculum statement 5: Healthy people—promoting health and preventing disease. Accessed via www.rcgp-curriculum.org.uk/PDF/curr_5_Healthy_people.pdf [date last accessed 16.09.2008].
RCGP. Curriculum statement 11: Sexual health. Accessed via www.rcgp-curriculum.org.uk/PDF/curr_11_Sexual_Health.pdf [date last accessed 16.09.2008].
Skidmore S, Horner P, Mallinson H. Testing specimens for Chlamydia trachomatis. Sexually Transmitted Infections (2006) 82(4):272–5.
Wilson JMG, Jungner G. Principles and practice of screening for disease (1968) Geneva (Switzerland): World Health Organization. (Public Health Paper Number 34).
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