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Volume 4 No 23; 11 June 2010

Major step forward in chlamydia screening in 2009/10

The National Chlamydia Screening Programme [1] (NCSP) aims to prevent and control chlamydia infection in young adults aged under 25 through opportunistic community-based testing. Preliminary results show the enormous progress that has been made by the NCSP in the past year. Over 1.5 million programme and other community-based tests (ie outside of Genitourinary Medicine (GUM) clinics) were conducted in 2009/10, an increase of 461,000 tests (44%) on the previous year (table 1). When combined with the estimated tests conducted in GUM clinics, a total of over 1.9 million chlamydia tests were done.

The current community-based test monitoring systems do not take account of repeat testing of individuals in the same setting within a year or between community settings and GUM clinics. The new GUM clinic information system, however, is able to link test data to individuals within each clinic and in 2008/9 and 2009/10 the number of individual young adults having chlamydia tests at GUM clinics was four-fifths of the number of tests conducted - ie within each year 1.26 tests were conducted for every attendee. Nevertheless, if it is assumed throughout this report - for both community-based tests and GUM clinic tests - that there is no repeat testing of individuals within the year, then in 2009/10 almost twice as many young women (39.9%) had a chlamydia test compared to young men (20.1%) (figure 1). Given that the programme aims to screen only the sexually active, estimated to be 82% of young women and 80% of young men aged 16 to 24 [2], then the proportions tested in 2009/10 were approximately 47% and 25% of sexually active young women and men respectively.

Estimated [1] number of chlamydia tests in those aged 15-24 in England by test category, sex, percentage infected, and year
Test category Gender 2008/09 2009/10
No. tested
No. +ve (%)
No. tested
No. +ve (%)
Programme tests

Females

505,800

40,000 (7.9%)

740,600

46,900 (6.3%)

Males

253,300

17,700 (7.0%)

460,500

22,800 (5.0%)

Other tests

Females

265,700 19,800 (7.5%) 277,400 17,500 (6.3%)

Males

23,800 3,000 (12.6%) 31,500 3,500 (11.1%)
All community-based tests

Sub-total

1,048,600 80,500 (7.7%) 1,510,000 90,700 (6.0%)
 
GUM clinic tests [1]

Females

323,300 36,600 (11.3%) 280,400 29,200 (10.4%)

Males

231,000 29,000 (12.6%) 192,800 23,100 (12.0%)
All GUM clinic tests [1]

Sub-total

554,300 65,600 (11.8%) 473,200 52,300 (11.0%)
 
ALL TESTS

Females

1,087,800 95,700 (8.8%) 1,293,800 93,000 (7.2%)

Males

505,300 50,000 (9.9%) 682,500 49,200 (7.2%)

TOTAL

1,593,100 145,300 (9.1%) 1,976,300 142,200 (7.2%)
1. See Statistical Notes on GUM clinic chlamydia test dataset at end.

 

Figure 1. Estimated [1] percentage of population [2] aged 15-24 in England tested for chlamydia by year, gender, and test category
1. See Statistical Notes on GUM clinic chlamydia test dataset at end.
2. Percentage tested calculated using 2008 ONS population data for 15-24 year olds: 3,523,198 males and 3,339,491 females.

There has been a large upsurge in community-based testing in 2008/9 and 2009/10 following the inclusion of annual objectives for chlamydia screening within the Vital Signs Indicator framework [3] (figure 2). Overall the proportion tested increased from 23.7% in 2008/9 to 29.9% in 2009/10 (figure 3). Most of this increase was due to programme tests. A parallel but much smaller increase between both years was seen in the numbers of other community-based tests, with annual numbers each year of the order of 300,000. Although substantial testing was conducted in young people attending GUM clinics, the estimated numbers declined from 554,000 in 2008/9 to 473,000 in 2009/10 (table 1). This decline was probably due to improved availability of community-based testing for young adults, as the estimated numbers of GUM clinic chlamydia tests in older age-groups increased over the same period.

The 2009/10 outcome of community-based testing was 90,700 infections detected in young adults, an increase of 10,200 infections detected compared to the previous year, and additional to the 52,300 infections ascertained through GUM clinic testing (table 1). Community-based testing found the proportion of women with chlamydia infection was 6.3% in 2009/10, while in men this proportion was 5% in programme tests and 11.1% in other tests (table 1). As expected with the substantial increase in the volume of community-based testing, the proportion infected in women and men declined somewhat between 2008/9 and 2009/10, both for programme tests and other tests. In both years the infection rate detected in GUM clinic tests for both women and men was substantially greater than the rate in those attending community-based services (table 1).

Figure 2. Estimated [1] number of chlamydia tests in those aged 15-24 in England by year [2] and test category
1. See Statistical Notes on GUM clinic chlamydia test dataset at end.
2. Data on GUM clinic and other tests by age-group not available prior to 2008/9.

 

Figure 3. Estimated [1] percentage of population [2] aged 15-24 in England tested for chlamydia by year [3] and test category

 



1. See Statistical Notes on GUM clinic chlamydia test dataset at end.
2. Percentage tested calculated using 2005-8 ONS population data for 15-24 year olds.
3. Data on GUM clinic and other tests by age-group not available prior to 2008/9.

 

Figure 4. Estimated [1] percentage of population [2] aged 15-24 tested for chlamydia in 2009/10 by English Strategic Health Authority and test category



1. See Statistical Notes on GUM clinic chlamydia test dataset at end.
2. Percentage tested was calculated using 2008 ONS population data for 15-24 year olds.

The percentage of young adults tested for chlamydia in 2009/10 in community-based settings varied across the Strategic Health Authorities of England from 26% in London to 16% in South Central (figure 4). When GUM clinic tests are included the range in coverage was from 39% in London to 24% in South Central.

Community based testing coverage of 25% and over in 2009/10 was achieved in a third of PCTs, and in a further third coverage was between 20% and 25% (figure 5).

These chlamydia screening outcomes are particularly encouraging given the recent results of the randomised control trial of a single chlamydia screen of young women in further education in south London which showed a 43% reduction in risk of pelvic inflammatory disease (PID) in the screened group (adjusted relative risk 0.57, C.I. 0.29 to 1.11) [4] and an 80% reduction in risk of PID among infected women who were treated. While it was encouraging that the trial indicated that screening may work to reduce PID in young women, it was disappointing it was not large enough to be conclusive about this question. Nevertheless, the study added to the evidence base concerning the health effects of chlamydia infection in young women, reinforced the screening policy being pursued by the NCSP, and emphasised the high levels of chlamydia infection in young sexually active women in England today.

The trial reported that one in ten to one in eleven of young women in the control group, who were later shown through testing their archived specimens to have had undiagnosed chlamydia infection when the study began, went on to develop PID during the following twelve months, compared to one of about 60 infected women who were screened initially and diagnosed and treated. Not surprisingly, the study found that most new cases of PID in this age group were probably related either to infections acquired after the single screening round or to other causes. This ongoing risk of chlamydia infection (and re-infection) has been addressed by the design of the NCSP since its inception. Rather than a single test, the national policy is to offer annual testing to all sexually active women and men under 25, and after they change sexual partners [1]. This testing policy is further strengthened by the recommended follow-up and treatment of the partners of any young adult found to be infected. The south London trial was not designed to study the additional effects, integral to the NCSP, of regular or repeated testing with partner notification.

Figure 5. Number of Primary Care Trusts in England meeting the 2009/10 objective for chlamydia screening [1] (25% [2,3]) of 15-24-year-olds



1. Community-based testing only, ie excluding GUM clinic testing.
2. The 2009/10 objective for chlamydia screening in the suite of Vital Signs Indicators (VSI) was 25% coverage of 15-24 year olds
3. Percentage tested was calculated using 2008 ONS population data for 15-24 year olds.

 

The January 2010 Public Accounts Committee Report (PAC) [5] on the National Audit Office value for money study [6] of the NCSP called on the Department of Health (DH) to make the Programme 'a national response to a national problem'. The PAC wants the Programme to improve efficiency, and to have better evaluation. Health Protection Agency plans are at an advanced stage to begin a population-based prevalence indicator survey to monitor the Programme's impact on the level of infection, thus addressing one of the key recommendations of the NAO [6]. Monitoring of the effect of chlamydia screening on health outcomes such as PID and other sequelae is underway, but given the limitations of observational data and the range of causes of these conditions, it may be difficult to draw conclusions about the effects of the programme on these outcomes.

The NCSP in England aims to test sexually active under 25s, once a year or after a change of sexual partner, by offering tests in general practice, sexual and reproductive health services, pharmacies, and other venues they visit [1]. While the benefit to individual patients of testing and appropriate treatment is indisputable [7] the optimal strategy for controlling chlamydia infection is debatable and likely to remain so for some time [7,8]. Meanwhile, the delivery of chlamydia screening in England has taken a major step forward and the NCSP is well set to achieve population testing levels fit to meet its aims.

Statistical Notes on GUM clinic chlamydia test dataset

1. Analyses were based on data returned by 7 June 2010. Data from 190 clinics were included. Another 17 GUM clinics have yet to submit data. For these 17 clinics, data was estimated from 2008 KC60 returns (the previous mandatory GUM clinic workload monitoring system).

2. Where GUM clinics have not returned data for the eight most recent quarters, the estimated test numbers and proportion infected were interpolated for any missing quarters. If Quarter 1 2010 data was missing, Quarter 1 2009 data was used instead. If that clinic also did not submit Quarter 1 2009 data, then the nearest quarter of submitted data was used (ie Quarter 2 2009). This rule was followed for all missing data returns.

3. Analyses include the total number of tests in those aged 15-24.

4. Within the dataset, patients were only allowed to have one chlamydia test each week, similar to the rule applied within the data for community-based tests.

5. Chlamydia diagnoses (table 1) were attributed to a chlamydia test if the diagnosis was within six weeks of a sexual health screen; only one chlamydia diagnosis was allowed per six week period; chlamydia tests within six weeks of the latest date of returned data (usually 31 March 2010) were excluded as this did not leave a maximum follow-up time for recording a chlamydia diagnosis.

6. For the regional analysis (figure 4), the GUM clinic test data is by region of clinic attended rather than region of residence.

References

1. National Chlamydia Screening Programme website, http://www.chlamydiascreening.nhs.uk/ps/index.html.

2. Johnson AM, Mercer CH, Erens B, Copas AJ, McManus S, Wellings K, et al. Sexual behaviour in Britain: partnerships, practices, and HIV risk behaviours. Lancet. 2001; 358:1835-42.

3. Department of Health. Monitoring the uptake of chlamydia screening - Vital Signs indicator 2008/09. Gateway 9952 May 2008, http://www.chlamydiascreening.nhs.uk/ps/assets/pdfs/data/VSI_AlanHall_Gateway_9952.pdf.

4. Oakeshott P, Kerry S, Aghaizu A, Atherton H, Hay S, Taylor-Robinson D, et al. Randomised controlled trial of screening for Chlamydia trachomatis to prevent pelvic inflammatory disease: the POPI (prevention of pelvic infection) trial. BMJ. 2010; 340: 903.

5. House of Commons Committee of Public Accounts. Young people's sexual health: the National Chlamydia Screening Programme. London: The Stationary Office: January 2010, http://www.publications.parliament.uk/pa/cm200910/cmselect/cmpubacc/283/283.pdf.

6. National Audit Office. Department of Health - Young people's sexual health: the National Chlamydia Screening Programme. London: The Stationary Office. November 2009, http://bit.ly/mCuWw.

7. Kalwij S, Macintosh M, Baraitser P. Screening and treatment of Chlamydia trachomatis infections. BMJ. 2010; 340: 912-17.

8. Gottlieb SL, Berman SM, Low N. Screening and treatment to prevent sequelae in women with Chlamydia trachomatis genital infection: how much do we know? J Infect Dis. 2010 Jun 15; 201 Suppl 2: S156-67.