Using chlamydia positivity to estimate prevalence: evidence from the Chlamydia Screening Pilot in England

Studies have suggested that positivity can be used to estimate the prevalence of Chlamydia trachomatis in large-scale chlamydia screening programmes. A recent pilot of opportunistic screening in England estimated that the prevalence among 16–24-year-old women in Portsmouth and Wirral was 9.8% and 11.2%, respectively. This study assessed the continued validity of positivity as an approximate for prevalence. We re-analysed data from the Chlamydia Screening Pilot to estimate positivity, calculated as total positive tests divided by total tests, and compared these estimates with the previously reported prevalence, measured as the number of women testing positive divided by the total number of women screened. Overall positivity was 9.4% in Portsmouth and 11.0% in the Wirral; these estimates were not statistically different from prevalence, regardless of health-care setting, age group or symptoms. We conclude that positivity can be used as a proxy for prevalence.

Finding cases of Trichomonas vaginalis infection in England

We describe the use of a new molecular assay for Trichomonas vaginalis (TV), the Gen-Probe Aptima TV (ATV) in female attendees at community clinics, a genitourinary (GU) medicine clinic and a prison GU medicine service. Positivity rates at community clinics and GU medicine were 0/382 (0%) and 3/358 (0.8%, 95% confidence interval [CI] 0–1.7%), respectively. Positivity was significantly higher, 29/269 (10.8%, 95% CI 7.1–14.5%), odds ratio (OR) 14.3 (4.11 < OR < 59.55), in those tested at the prison. A questionnaire survey of English GU medicine clinics and data from the UK Health Protection Agency (HPA) for England both demonstrated the large variation in case rates by region and testing methods employed. Higher rates were seen in women, in prison GU medicine services and in London GU medicine clinics. The ATV assay is now CE-marked (Conformité Européenne) and so a larger prospective study of its potential application is warranted.

Shortening the voiding interval for men having chlamydia nucleic acid amplification tests

Male patients are assessed for a sexually transmitted infection provided a considerable length of time has elapsed since last micturition. The current availability of highly sensitive nucleic acid amplification tests (NAATs) for Chlamydia trachomatis (CT) and Neisseria gonorrhoea such as APTIMA Combo2 (AC2) led us to investigate the impact of voiding interval on the positivity of urine tests for CT. Male patients attending a genitourinary medicine clinic at high clinical risk for CT infection and known CT positives returning for treatment were included. Two first-void urine (FVU) specimens were collected: the first sample in the standard manner and the second sample was collected 20 minutes later or as soon as possible thereafter. Fifty-two CT-positive males were included in the analysis. All of the second samples were also CT positive and none were in the equivocal range. Paired t-test analysis did not show a significant difference between relative light unit readings of the first and second urine samples (P = 0.127). Even in male patients who have recently passed urine, FVU tested by AC2 can still reliably detect CT. This provides us opportunity for more flexible and effective patient management.

Diagnosis, management and prevalence estimation of gonorrhoea: influences of Aptima Combo 2 assay with alternative target confirmation

Case-notes and laboratory data were retrospectively reviewed for influences of dual testing by Aptima Combo 2 (AC2) for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) on the diagnosis, management and prevalence estimation of gonorrhoea in the genitourinary (GU) medicine clinic and community. NG positives by AC2 were confirmed by Aptima Gonococcus assay. Unconfirmed positives were rare. Our study showed that in the GU medicine clinic, AC2 detected about 20% extra cases of NG beyond culture. For best standard of care, NG culture and microscopy are still required in some patients to ensure that treatment is rapid and appropriate. Compared to self-referral at the GU medicine clinic, community tests made a substantial contribution to the overall number of NG cases found (40 community versus 35 Macclesfield GU medicine clinic). The ratio of female to male NG cases found was significantly higher (P = 0.002) in the community (13 M, 27 F) than at the GU medicine clinic (25 M, 10 F). In the community, over 60% of NG infections occurred in chlamydia-negative patients. The overall prevalence of NG in the GU medicine clinic was 1.3%, the true prevalence being much lower at 0.9% on primary test. Prevalence in the community was 0.4%. Data from dual testing in the community can clarify NG prevalence beyond the existing KC60 (sexually transmitted infections) reports.

Confirmation of BD ProbeTec Neisseria gonorrhoeae reactive samples by Gen-Probe APTIMA assays and culture

BACKGROUND

Use of nucleic acid amplification tests (NAATs), such as strand displacement assay (SDA), for the detection of gonococcal infection in low prevalence populations is controversial because of the likelihood of false positive results. Use of supplementary NAATs with alternative target sites has been recommended for confirmation of primary NAAT results.

AIM

To evaluate if SDA reactive specimens for Neisseria gonorrhoeae, which were either culture positive or negative, can be confirmed by alternative target NAATs such as transcription-mediated assays (TMA).

METHODS

SDA reactive specimens were retested by TMA using APTIMA Combo 2 (AC2) and APTIMA GC (AGC) assays. Two different methods of specimen preparation were used to test the specimens. In method A, residual extract after SDA was retested and in method B, the original clinical specimen was re-extracted in TMA medium and then retested. Cervical or urethral swabs were requested to confirm the SDA results by culture.

RESULTS

By method A, 26/49 (53.1%) of SDA positive specimens were positive by AC2 and/or AGC; 14/27 (51.8%) culture confirmed SDA positive tests were positive by AC2 and/or AGC. By method B, 38/39 (97.3%) SDA positive results were confirmed by both AC2 and AGC. All the 25 culture confirmed SDA positive tests were confirmed by both AC2 and AGC; 5/6 SDA positive tests that were culture negative were confirmed by both AC2 and/AGC.

CONCLUSION

Alternative target site NAATs, such as AC2 and AGC, can be used to confirm SDA positive results using the same clinical specimen. There is high concordance between the three NAATs.

The contribution of APTIMA Combo 2 assay to the diagnosis of gonorrhoea in genitourinary medicine setting

For 929 female and 821 male patients attending a genitourinary clinic, samples intended for chlamydia diagnosis were dual tested by nucleic acid amplification for both chlamydia and Neisseria gonorrhoeae (NG). The assay used, Gen-probe APTIMA Combo 2 (AC2) detected all cases of NG found by conventional microscopy and culture. AC2 identified additional patients who had partners with NG, but were themselves negative by microscopy and culture. Few, if any, false-positive AC2 results were found. Use of AC2 increased the number of patients treated for NG. It can reduce the number of specimens required and may limit the need for multiple site testing.

No evidence of the Chlamydia trachomatis variant in the UK

OBJECTIVES

The discovery of a variant strain of Chlamydia trachomatis (Ct) in Sweden has raised awareness of its possible undetected spread in the UK. The assays that fail to detect this variant are widely used in this country. This study aimed to determine if this variant is circulating in the UK.

METHOD

1,680 genital specimens tested negative by the Roche assays were retested by Aptima Combo2. Discordant results were sequenced to check for the deletion variant.

RESULTS

Of 1,680 specimens tested, 29 were candidates for sequencing: 16 were negative for the variant, 11 failed to amplify, and 2 were lost.

DISCUSSION

No Ct deletion variants were found in the UK. If it is circulating, then the prevalence is low (0-0.77%), but even a low level cannot be ignored. The system we describe is simple and suitable for rapid response and phasing of surveillance to match an unknown level of threat if other variants emerge.

Should we consider alternatives to combined cervical and urethral swabs for detection of Chlamydia trachomatis in females?

BACKGROUND

The optimum approach for detecting Chlamydia trachomatis (CT) is considered to be combined cervical and urethral testing.

OBJECTIVE

To assess the contribution of female urethral swabs in CT diagnosis and to examine alternatives.

METHOD

Urethral and endocervical samples for CT were performed on 757 sexually active female patients, >16 years, attending the genitourinary medicine clinic at Macclesfield District General Hospital from October 2005 to November 2006. Swabs were collected and transported to the laboratory in separate AC2 sample collection tubes and were tested by AC2 assay.

RESULTS

Of the 757 patients tested simultaneously by both endocervical and urethral swab, a total of 90 had CT identified by either method giving a positivity rate of 11.9%. Results for urethral and endocervical swabs were concordant in 77 patients (85.6%). Eighty two infections (91.1%) would have been diagnosed by swabbing the cervix only but an additional 8 (8.9%) were picked up by urethral swab. Urethral symptoms had been mentioned by 1 of these 8 women.

CONCLUSION

8.9% infected women were positive only on urethral swab. One of these would have been picked up owing to presenting symptoms, hence reducing the extra yield to 7.8% and leaving only 7 positives on 757 urethral swabs with a detection rate of 1% of all urethral swabs. Considering the low yield and the discomfort of urethral swabbing, an additional urethral swab appears unwarranted on grounds of both cost and patient care. As a small number of cases were detected at the urethra but not the cervix, it may be worthwhile investigating the performance of AC2 when placing an endocervical swab in first catch urine. An effective and simpler approach may be a switch to testing vaginal swabs by AC2.

Risk factors associated with pelvic inflammatory disease

OBJECTIVE

To investigate factors associated with pelvic inflammatory disease (PID).

METHODS

A case-control study was used to investigate demographic and behavioural factors, and causative agents associated with PID.

RESULTS

A total of 381 participants were recruited: 140 patients, and 105 and 136 controls in tubal ligation and general practice groups, respectively. When compared with a PID-free tubal ligation control group, increased risk of PID was associated with: age <25 years; age at first sexual intercourse <20 years; non-white ethnicity; not having had children; a self-reported history of a sexually transmitted disease; and exposure to Chlamydia trachomatis. When compared with a general practice control group, increased risk was associated with: age <25 years; age at first sexual intercourse <15 years; lower socioeconomic status; being single; adverse pregnancy outcome; a self-reported history of a sexually transmitted disease; and exposure to C trachomatis. Of the cases, 64% were not associated with any of the infectious agents measured in this study (idiopathic).

CONCLUSIONS

A high proportion of cases were idiopathic. PID control strategies, which currently focus on chlamydial screening, have to be reviewed so that they can prevent all cases of PID. Behavioural change is a key factor in the primary prevention of PID, and potential modifiable risk factors were associated with PID.

Should Chlamydia trachomatis confirmation make you cross? Performance of collection kits tested across three nucleic acid amplification test platforms

OBJECTIVE

To investigate the feasibility of confirming initially reactive nucleic acid amplification assays for Chlamydia trachomatis (CT) by cross testing on a second molecular platform. The three platforms investigated were Aptima Combo 2 assay (AC2), Cobas Amplicor CT test (PCR) and ProbeTec ET CT assay (SDA).

METHODS

Serial dilutions of a CT culture were prepared in 0.9% saline; used to prepare simulated swab samples for all three platforms, and tested as in the manufacturer's instructions. For the cross testing investigation, 1 ml of the simulated swab samples prepared in each of the three collection kits was transferred into the appropriate collection kit for the second platform.

RESULTS

AC2 demonstrated a higher analytical sensitivity than the SDA and PCR assays. Upon cross testing AC2 again demonstrated a superior performance to the SDA and PCR assays even when testing swab samples originally prepared in the SDA and PCR transport medium. The SDA assay was inhibited by the addition of transport medium from both the AC2 and PCR assays.

CONCLUSION

The analytical sensitivity of the three assays is not identical, therefore confirming initially reactive samples on a second platform may prove to be difficult. However, the higher sensitivity of the AC2 assay could allow its use as a confirmatory assay for reactive swab samples collected in the SDA and PCR transport medium.

Testing specimens for Chlamydia trachomatis

The introduction of NAATs has revolutionised chlamydial diagnostics and these tests are now the standard of care. However, as with all new technologies, they have also presented new challenges. This review attempts to answer some of the questions that have been raised, particularly by groups about to embark on implementing a screening programme. Laboratory tests are continually changing but it is hoped that the paper provides a useful update of the current situation.

Finding, confirming, and managing gonorrhoea in a population screened for chlamydia using the Gen-Probe Aptima Combo2 assay

OBJECTIVES

To identify the prevalence of Neisseria gonorrhoeae (NG) within a population screened for Chlamydia trachomatis (CT). To monitor confirmatory microscopy, culture, and partner findings following reactive Aptima Combo2 assay (AC2) gonorrhoea screening tests.

METHODS

Between June and December 2004, all gonorrhoea screening tests performed using AC2 for clients taking part in the Liverpool Chlamydia Screening Programme were monitored. Clients with AC2 NG reactive results were referred to a local genitourinary medicine (GUM) department for confirmatory microscopy, culture, treatment, and partner follow up.

RESULTS

47 (1%) of 4680 women and eight (1.7%) of 473 men had AC2 reactive gonorrhoea screening tests. Of those clients who agreed to follow up and were tested before any treatment, supportive evidence for a gonorrhoea diagnosis was found in 37 (97%) of 38 women and all five men. In the population opportunistically screened for chlamydia, CT prevalence rates were 12% for women and 15.7% for men. Although both women and men showed a higher relative risk for NG if chlamydia positive, of the 47 women who were reactive for NG by AC2, 55% (26) were negative for chlamydia.

CONCLUSIONS

Sexually transmitted infections are rising in England and reduction of gonorrhoea rates is an objective of the Department of Health Sexual Health and HIV Strategy. AC2 tests provide an acceptable and accurate means of testing for gonorrhoea in an asymptomatic population in the community. AC2 had a higher positive predictive value than might be suggested by previous clinical trials in this low prevalence population. Although antibiotic sensitivity must be monitored, AC2 testing may offer a more acceptable alternative to microscopy and culture for NG in some populations.

Scrotal mass with fever and generalized lymphadenopathy in a young man secondary to Chlamydia trachomatis infection

A young man presented with systemic upset and generalised lymphadenopathy. Later, it transpired that he was under investigation for a scrotal mass. Investigations were carried out to ascertain the cause of his symptoms including lymph node biopsy. Because of the presence of a scrotal mass in a sexually active male, a urinary Chlamydia ligase chain reaction (LCR) test was carried out. The result was positive and he was treated with doxycycline for 2 weeks. His symptoms settled and further, the urinary LCR was negative. We propose that Chlamydia trachomatis infection caused his illness and that urine PCR or LCR tests for Chlamydia is a convenient and useful investigation in sexually active males with generalised lymphadenopathy and fever of unknown origin.

Liquid based cytology: examination of its potential in a chlamydia screening programme

OBJECTIVE

To assess the feasibility of testing for chlamydia directly on a single liquid based specimen (ThinPrep test) collected for cervical screening.

METHOD

Cervical smears were taken using a Cervex spatula and rinsed in the liquid based cytology collection vial. Following this, the conventional sample for chlamydia testing was taken from the endocervix using an Abbott Collection kit. Cytological specimens were prepared using an automated slide processor. Residual cellular material and the conventional samples were sent to the laboratory where both were tested for chlamydia by ligase chain reaction (LCR). The manufacturer's protocol for LCR urine testing was modified to substitute 1 ml of PreservCyt suspension.

RESULTS

581 women had both swab and cytology suspension tested for Chlamydia trachomatis with LCR. There were 19 concordant positive and 562 concordant negative reports. The stability of chlamydia in the cytology suspension was maintained for at least 5 months.

CONCLUSION

The findings lead us to conclude that samples collected for liquid based cytology using the ThinPrep test collection vial provide a potential platform for chlamydia screening, though the study established several issues to be addressed to make this a practical proposition.

Associations between Mycoplasma genitalium, Chlamydia trachomatis and pelvic inflammatory disease

OBJECTIVE

To evaluate the association between Mycoplasma genitalium, Chlamydia trachomatis, and pelvic inflammatory disease (PID) METHODS: A case-control methodology was used. Swab eluates were processed using the QIAamp DNA mini kit. Polymerase chain reaction (PCR) for M genitalium was carried out using a real time in-house 16S based assay. An endocervical swab was taken and tested for the presence of C trachomatis (ligase chain reaction, Abbott Laboratories), and a high vaginal swab was taken and tested for the presence of Neisseria gonorrhoeae and bacterial vaginosis.

RESULTS

Of the PID cases 13% (6/45) had evidence of M genitalium infection compared to none of the controls (0/37); 27% (12/45) of the cases had C trachomatis infection compared to none of the controls; and 16% (7/45) of cases only had serological evidence of C trachomatis infection compared to 5% (2/37) of controls. Cases were more likely to present with M genitalium and/or C trachomatis than controls (p<0.001).

CONCLUSIONS

This study indicates that there may be an association between M genitalium and PID, and that this relation is largely independent of C trachomatis. Future studies need to investigate the pathological basis of the relation between M genitalium and PID using samples from women with PID diagnosed using laparoscopy and endometrial biopsy. Little is known about the epidemiology of M genitalium: large scale epidemiological investigations are needed to determine the prevalence, incidence, and factors associated with this emerging infection.

Associations between Mycoplasma genitalium, Chlamydia trachomatis, and pelvic inflammatory disease

OBJECTIVE

To evaluate the association between Mycoplasma genitalium, Chlamydia trachomatis, and pelvic inflammatory disease (PID) METHODS: A case-control methodology was used. Swab eluates were processed using the QIAamp DNA mini kit. Polymerase chain reaction (PCR) for M. genitalium was carried out using a real time in-house 16S based assay. An endocervical swab was taken and tested for the presence of C. trachomatis (ligase chain reaction, Abbott Laboratories), and a high vaginal swab was taken and tested for the presence of Neisseria gonorrhoeae and bacterial vaginosis.

RESULTS

Of the PID cases 13% (6/45) had evidence of M. genitalium infection compared to none of the controls (0/37); 27% (12/45) of the cases had C. trachomatis infection compared to none of the controls; and 16% (7/45) of cases only had serological evidence of C. trachomatis infection compared to 5% (2/37) of controls. Cases were more likely to present with M. genitalium and/or C trachomatis than controls (p<0.001).

CONCLUSIONS

This study indicates that there may be an association between M. genitalium and PID, and that this relation is largely independent of C. trachomatis. Future studies need to investigate the pathological basis of the relation between M. genitalium and PID using samples from women with PID diagnosed using laparoscopy and endometrial biopsy. Little is known about the epidemiology of M. genitalium: large scale epidemiological investigations are needed to determine the prevalence, incidence, and factors associated with this emerging infection.

Opportunistic screening for genital chlamydial infection. I: acceptability of urine testing in primary and secondary healthcare settings

OBJECTIVES

To determine the acceptability of opportunistic screening for Chlamydia trachomatis in young people in a range of healthcare settings.

DESIGN

An opportunistic screening programme (1 September 1999 to 31 August 2000) using urine samples tested by ligase chain reaction (LCR). Data on uptake and testing were collected and in-depth interviews were used for programme evaluation.

SETTING

General practice, family planning, genitourinary medicine clinics, adolescent sexual health clinics, termination of pregnancy clinics, and women's services in hospitals (antenatal, colposcopy, gynaecology and infertility clinics) in two health authorities (Wirral and Portsmouth and South East Hampshire). Main participants: Sexually active women aged between 16 and 24 years attending healthcare settings for any reason.

MAIN OUTCOME MEASURES

Uptake data: proportion of women accepting a test by area, healthcare setting, and age; overall population coverage achieved in 1 year. Evaluation data: participants' attitudes and views towards opportunistic screening and urine testing.

RESULTS

Acceptance of testing by women (16-24 years) was 76% in Portsmouth and 84% in Wirral. Acceptance was lower in younger women (Portsmouth only) and varied by healthcare setting within each site. 50% of the target female population were screened in Portsmouth and 39% in Wirral. Both the opportunistic offer of screening and the method of screening were universally acceptable. Major factors influencing a decision to accept screening were the non-invasive nature of testing and treatment, desire to protect future fertility, and the experimental nature of the screening programme.

CONCLUSIONS

An opportunistic model of urine screening for chlamydial infection is a practical, universally acceptable method of screening.

Opportunistic screening for genital chlamydial infection. II: prevalence among healthcare attenders, outcome, and evaluation of positive cases

OBJECTIVES

To determine the prevalence and treatment outcomes among young women screened opportunistically for genital Chlamydia trachomatis and to evaluate the impact of screening in those participating.

DESIGN

An opportunistic screening programme (1 September 1999 to 31 August 2000) using urine samples, tested by ligase chain reaction (LCR). In-depth interviews were used for programme evaluation.

SETTING

Screening was offered in two health authorities at general practice, family planning, genitourinary medicine (GUM), adolescent sexual health, termination of pregnancy clinics and women's services in hospitals (antenatal, colposcopy, gynaecology and infertility clinics). Main participants: Sexually active women (16-24 years) attending for any reason.

MAIN OUTCOME MEASURES

Screening data: prevalence of infection by age and healthcare setting; proportion of positive patients attending for treatment. Evaluation data: participants' attitudes and views towards screening and follow up.

RESULTS

In total, 16 930 women (16-24 years) were screened. Prevalence was higher in younger women (16-20) than those aged 21-24 years and was highly variable at different healthcare settings (range 3.4%-17.6%). Prevalence was approximately 9% in general practice. The role of the project health advisers in managing results and coordinating treatment of positive individuals was essential; the vast majority of all positives were known to be treated. Women felt that screening was beneficial. Improving awareness and education about sexually transmitted infections is required to alleviate negative reactions associated with testing positive for infection.

CONCLUSIONS

Prevalence of infection outside GUM clinics is substantial and opportunistic screening using urine samples is an acceptable method of reaching individuals with infection who do not normally present at specialist clinics.

Evaluation of the specificities of five DNA amplification methods for the detection of Neisseria gonorrhoeae

The intragenus specificities of five molecular diagnostic methods for Neisseria gonorrhoeae were determined. Three assays were considered suboptimal. Molecular detection of N. gonorrhoeae from sites where other Neisseria spp. commonly occur or from any site in low-prevalence settings should be confirmed by a test targeting a different genetic locus.

Provision of chlamydia testing in a nationwide service offering termination of pregnancy: with data capture to monitor prevalence of infection

OBJECTIVES

To establish a methodology by which all women attending for termination of pregnancy (TOP) at British Pregnancy Advisory Service (BPAS) branches may be approached to participate in Chlamydia trachomatis screening. To examine the feasibility of monitoring C trachomatis prevalence and the impact of charging for screening on the uptake rate in this population.

METHODS

Patients attending for TOP at participating BPAS branches were offered a test for chlamydia infection and asked to complete a questionnaire. Urine samples from participants were tested using a nucleic acid amplification test (NAAT).

RESULTS

1001 women provided a urine sample, a 77% response rate among those participating in the study. Factors significantly associated with taking up chlamydia screening included symptoms, previous TOP, parity, and no previous chlamydial test. Overall prevalence of genital chlamydial infection was 7.5%, with highest age specific prevalences occurring among attendees aged 20-24 years (11.5%) and under 20 years (10.8%). In univariate analysis, chlamydia positivity was significantly associated with respondent age and previous diagnosis with chlamydia. Only 35% of women who had the screening test would have done so had they been asked to pay the pound 20 clinical, administrative, and laboratory costs of the examination.

CONCLUSIONS

We have demonstrated the feasibility of routine chlamydia screening and the potential for prospective prevalence monitoring across the nationwide BPAS service. In most cases the chlamydia result was available within the clinical contact period for the TOP. Charging patients directly for the test could reduce uptake of chlamydia screening to levels unsatisfactory for both the public health and prevalence monitoring purposes.

Outreach health adviser in a community clinic screening programme improves management of genital chlamydia infection

OBJECTIVE

To assess the effectiveness of an outreach health adviser on treatment, partner notification and outcome for clients diagnosed with genital chlamydia (CT) infection at a community young people's clinic.

METHODS

From August 1999 to March 2000, a genitourinary medicine (GUM) based health adviser helped to develop testing and undertook outreach management of clients aged under 26 years diagnosed with CT infection. In addition to facilitating referral to GUM, she gave antibiotic treatment based on a GUM derived patient group direction to those not wishing to travel to the GUM clinic. She also advised them on contact tracing and the need for a compliance check (CC).

RESULTS

Chlamydia positive tests with ligase chain reaction (LCR), on first void urine, were obtained for 62 (12.9%) of 481 female clients, one (5%) of 20 male clients, and nine (53%) of 17 male contacts of female positive cases. All 72 testing positive received their result and were treated. Two urine samples positive for CT showed positive LCR tests for gonorrhoea. Proportions of named contacts seen (67%) and reattendances for compliance checks (60%) were similar to those for women seen in GUM services.

CONCLUSIONS

Health adviser input with the ability to treat can be effective in reducing the growth of identified but untreated genital chlamydia infection consequent upon community based screening. Such a strategy appears comparable with, and can add to, GUM based treatment of infection. It helps to address the need for alternative management strategies in the light of the national sexual health strategy.

What is needed on a laboratory test request form?

In the development of a screening programme for genital tract Chlamydia trachomatis infection, a modified test request form was devised and used successfully both to request the test, to collect data and to inform patients. Our examination of the practicalities and ethical and confidentiality issues involved in making a request for a laboratory test to assist clinical diagnosis or management, resulted in the introduction of extra features that we had not previously seen used in the design of request forms. Coded response boxes can have adjacent questions attached as a perforated strip. Removal of this question strip leaves a completed form with no explicit sensitive data (figure 2). A detachable information sheet for patients can also be incorporated into the request form (figure 1). The design of a request form raises issues that do not appear to have been widely or formally debated.

Comparison of urine, first and second endourethral swabs for PCR based detection of genital Chlamydia trachomatis infection in male patients

OBJECTIVES

To compare endourethral swabs and urine as diagnostic specimens for the detection of genital Chlamydia trachomatis infection using the polymerase chain reaction (PCR), in male patients attending a genitourinary clinic and to assess whether the first endourethral swab used solely for diagnosing gonococcal infection could be used for C trachomatis detection as well.

METHODS

Two endourethral swabs were taken from 80 male patients, in whom the likelihood of genital C trachomatis infection was high. The first swab was used for microscopy and culture for Neisseria gonorrhoeae, before being used for C trachomatis detection. First voided urine specimens were collected from 61 of these patients. All three specimens were processed for C trachomatis DNA detection using the Roche Cobas Amplicor PCR. A diagnosis of genital C trachomatis infection was made if any one of the specimens tested reproducibly positive. Samples from 13 patients showing discrepant PCR results between swabs and/or urine were retested by ligase chain reaction (LCR).

RESULTS

Chlamydia trachomatis DNA was detected in 35 (43.8%) of the 80 patients. In 17 of the 35 patients (48.6%), all the genital specimens were positive. However, in 18 (51.4%) patients, one or more of the genital specimens had negative PCR results. Among the 18 patients with discrepant results, urine was found to be a more sensitive diagnostic specimen than the second urethral swab picking up 13 out of 16 positives (81.3%) as opposed to five out of 18 (27.8%). There was no significant difference between the two swabs. Retesting by LCR, of the samples from 13 of the 18 patients with discrepant PCR results confirmed them all as true positives, although as with PCR, not all specimens in the set were concordantly positive. LCR detected all the 13 positives in urine, while there was no difference in the detection rate between the first and the second urethral swabs.

CONCLUSIONS

Urine appeared to be a better diagnostic specimen than the conventional second endourethral swab for C trachomatis detection by PCR in this cohort of male patients. There was no difference between the first swab, intended primarily for N gonorrhoeae testing and the second swab intended for C trachomatis detection. This raises questions over the need for the conventional second swab for detecting C trachomatis.

Evaluation of near patient testing for Chlamydia trachomatis in a pregnancy termination service

AIM

To identify and evaluate advantages and disadvantages of a near patient test (NPT) for Chlamydia trachomatis, using Clearview Chlamydia MF (Unipath Ltd) in a British Pregnancy Advisory Service (BPAS) clinic.

METHOD

The improved Clearview Chlamydia MF test was used to test endocervical swabs from 400 women attending BPAS clinic for termination of pregnancy. The results were compared with Ligase Chain Reaction (LCR), using Polymerase Chain Reaction (PCR) as the arbiter.

RESULTS

Twenty-seven women tested positive by Clearview Chlamydia MF (24 confirmed by LCR) and 32 by LCR.

COMMENT

NPT has potential advantages in specific situations where a quick result is required for optimal management of those testing positive. However, the current technology available for detection of Chlamydial infection results in time constraints, which limited its benefits in this study, where there was a high throughput of clients. A significant number of cases were missed by Clearview Chlamydia MF, though the sensitivity found is within the ranges reported for various enzyme immunoassays (EIA) - currently the most commonly used testing method. The study confirmed the high positivity in those attending for termination, especially in under 25-year-olds.

Management of Chlamydia trachomatis in a women's hospital: a review of current practice

OBJECTIVE

To establish a measure of testing for Chlamydia trachomatis within the Liverpool Women's Hospital with a view to optimising both testing and management of infection.

DESIGN

Prospective observational study to review the outcome of Chlamydia testing and subsequent management of patients between September 1997 - September 1998.

RESULTS

It was observed that opportunities for detecting infection were missed and testing was undertaken predominantly for diagnostic purposes.

RECOMMENDATION

Consideration be given to a centralised system for overview of positive results linking with audit/education to reduce sequelae of Chlamydia within gynaecology.

Chlamydia trachomatis screening in young people in Merseyside

OBJECTIVES

To evaluate the acceptability to young people of proactive Chlamydia trachomatis (CT) information and urine test. To discover the extent of CT infection and the practical implications for completing treatment and partner notification.

DESIGN

Prospective screening with sexual health questionnaire.

SETTING

Three family planning clinics for young people in Liverpool and South Sefton.

PARTICIPANTS

Nine hundred and five women and 53 men had urine tests and answered the questionnaire. All aged 20 years or under attending the clinics were given information about CT and safer sex.

MAIN OUTCOME MEASURES

The acceptability of proactive information and screening for CT using a urine test. Prevalence of CT infection. The time and effort incurred informing and managing those testing positive.

RESULTS

The information and urine test were readily accepted. Prevalence of CT was 8.5% in women and 5.7% in men. More than three-quarters of those testing positive were treated, but it took much time and effort, as follow-up attendance was poor.

CONCLUSIONS

The prevalence of CT was high in this population. Young people participated in screening readily. They are interested in this health issue, but it was difficult to hold their attention long enough to complete the process of treatment and contact tracing. Completing this successfully either needs a huge input of resources or a new approach. These results have led to the piloting of an outreach health adviser administering treatment and carrying out partner notification at the screening site. Some of the questions raised by the CMO have been addressed.

Changing screening strategies for genital chlamydia in family planning clinics: a good public health strategy?

OBJECTIVE

To estimate the prevalence and factors associated with genital chlamydia in 1996 and to evaluate the introduction of restricted screening criteria based on diagnostic testing and prevention of iatrogenic pelvic inflammatory disease in 1997.

PATIENTS

Women attending Liverpool family planning clinics.

METHOD

Clinical and demographic data were recorded at routine clinic consultations. Data were analyzed using logistic regression.

RESULTS

In 1996, a 5.7% (123/2165) chlamydial prevalence was detected. A significantly lower prevalence was observed in the over-25-year-old age group compared to those aged 16-19 years old (p < 0.0001), and in those with an interval of over 11 months since the last new sexual partner compared to those with a new partner in the past 1-3 months (p < 0.05). A significantly higher prevalence was detected in those only presenting with signs of infection alone compared to those presenting with either symptoms or both signs and symptoms of infection (p < 0.05). Those requesting a termination of pregnancy were at higher risk of genital chlamydia than those attending for contraceptive advice (odds ratio 1.97; 95% confidence interval 1.14-3.39). Using the restricted screening criteria, prevalences of 5.4% (78/1438) and 3.7% (60/1641) were found for 1996 and 1997, respectively. Prevalences were significantly higher in 1996 than 1997 when adjusted for the other factors (p < 0.05).

CONCLUSION

The study raised awareness of genital chlamydia among women attending family planning clinics and showed that primary care could make a significant contribution to the prevention of chlamydial infection. It is only by initiating intervention strategies in such settings that genital chlamydia will be controlled effectively in the UK.

Hepatitis B and hepatitis C virus infections: risk factors among drug users in Northwest England

OBJECTIVES

to identify the risk factors for hepatitis B (HBV) and hepatitis C (HCV) virus infections in drug users attending two drug treatment centres in Northwest England, and to evaluate the effect of both needle exchange and hepatitis B vaccination on the prevalence of hepatitis B and hepatitis C infections.

METHODS

a retrospective, cross-sectional study performed at the Regional Infectious Disease Unit and a Primary Care Centre for drug users in Liverpool. The study population included 773 drug users who had hepatitis serology performed between January 1992 and April 1996. Information on risk factors was obtained from clinical records; hepatitis serology data were obtained from the Liverpool Public Health Laboratory database.

RESULTS

the overall seroprevalences of exposure markers for HBV (anti-HBc antibody) and HCV (anti-HCV antibody) were 48% and 67%, respectively. Duration of injecting drug use was the strongest predictor of HCV infection, with a crude odds ratio of 8.9 (95% confidence interval (CI): 4.5-17) for >10 compared to <3 years of injecting, and was also a strong predictor of HBV infection, with an adjusted odds ratio (controlled for the effects of HBV vaccination) of 5.7 (95% CI: 3.2-10) for >10 compared to <3 years' injecting. Vaccination against HBV was associated with greatly reduced HBV seroprevalence (crude odds ratio 0.11, 95% CI: 0.06-0.18). Overall, HCV was acquired earlier in the injecting career than HBV, but drug users who were not vaccinated against HBV acquired markers for HBV even more rapidly than for HCV. We found no independent protective effect for either anti-HBc or anti-HCV acquisition after the introduction of a needle-exchange scheme.

CONCLUSIONS

hepatitis C is highly prevalent among Merseyside drug users and is likely to prove difficult to control because of rapid acquisition early in the injecting career. Vaccination against hepatitis B is the best means of protecting drug users from hepatitis B, and should be offered before injecting is commenced.

There is more to a test than technology-evaluation of testing for chlamydia infection in a charitable sector termination service

In order to develop a possible strategy for chlamydia testing throughout the British Pregnancy Advisory Service (BPAS), it was decided to first find the prevalence of the infection in women attending and to examine the practicalities involved in offering tests and dealing with positive results. Urine samples at initial consultation were tested by a method based on the Ligase Chain Reaction (LCR). Five hundred and eighty seven women were tested with an overall chlamydia positivity of 8.1 per cent, but of 12.4 per cent (25/202) in women up to and including 20 years of age. Tests in women over 25 years showed a positivity of only 0.7 per cent (1/147). Urine testing proved to be a convenient, non-intrusive means of chlamydia detection with the potential to lead to prompt management of positive cases. However, in comparison with EIA testing of endocervical swabs, detection of chlamydia in the population studied was not enhanced and some limitations were demonstrated, imposed by requirements for controlled temperature for transport and storage of specimens. Alternative approaches to testing and management was discussed. The time and commitment required to offer this service effectively were observed to be important factors when staff and client were focused on the direct issues relating to the current pregnancy. Modified request forms enabled uniform data to be collated in the laboratory and compared with that from other services currently studied. Ongoing monitoring of chlamydia positivity in this nationwide termination service could provide useful sentinel data about the infection.

Epidemiology of genital Chlamydia trachomatis in England and Wales

OBJECTIVE

To describe the recent epidemiology of genital Chlamydia trachomatis infection in England and Wales.

DESIGN

Retrospective study of routinely available surveillance datasets and ad hoc prevalence studies.

METHODS

Numbers of new cases of genital C trachomatis infection, obtained from the Department of Health and Welsh Office, were combined with the estimated mid-year resident population of England and Wales. Rates were analysed for trend over time using a log linear age period model in GLIM4. Ad hoc prevalence and case finding studies carried out over the past 20 years were critically assessed in terms of study design and testing methodologies.

RESULTS

Attendance rates at genitourinary medicine (GUM) clinics were higher for women than men over the period 1989 to 1994 as were the number of laboratory reports. The highest rate of attendance (GUM clinic data) was for women aged 16 to 19 years. There was an overall significant linear decrease in the attendance rates over time for both men (p = 0.0172) and women (p = 0.0000) between 1989 and 1994. There was considerable variation in the prevalence of genital C trachomatis infection detected within different clinical settings, together with a substantial level of asymptomatic infection.

CONCLUSIONS

Genital C trachomatis infection is broadly distributed throughout the sexually active population, with a substantial reservoir of asymptomatic infection among those generally perceived to be at low risk of a sexually transmitted infection. Young people, particularly women aged 16 to 19 years, are at highest risk of genital C trachomatis infection. This is of concern since younger women are more susceptible than older women to developing complications of chlamydial infection, such as pelvic inflammatory disease. The broad distribution of infection across all sexually active health service attenders and the high level of asymptomatic infection suggest that a new, screening based, approach to the control of genital C trachomatis infection is required. Recommendations are made as to the epidemiological research required to guide such work.

Serological diagnosis with the Chlamydia Spot-IF test

Using a set of sera for which full chlamydial micro-immunofluorescence results suggested a clear diagnosis, we have evaluated the Chlamydia Spot-IF test (bioMerieux), which allows a comparison of titres to Chlamydia trachomatis and C. psittaci antigens. A modification of the test in which the antigen slides were pre-treated with a monoclonal antibody to chlamydial lipopolysaccharide, improved its ability to differentiate infections with C. trachomatis from those with C. psittaci or C. pneumoniae.

Per-nasal swabbing as an aid to the diagnosis of chlamydial and adenovirus conjunctivitis

Two hundred and thirty four patients (adults and babies) with conjunctivitis were investigated by taking eye swabs and in addition by taking per-nasal swabs. Chlamydia trachomatis was isolated from 20 patients and adenovirus from 14 patients. Per-nasal swabbing led to a 53% increase in chlamydia diagnosis and a 27% increase in the diagnosis of adenovirus infection. It is suggested that per-nasal swabbing has an important role to play in detecting chlamydial conjunctivitis which itself may be an indicator for high morbidity in patients and their contacts.

Adult follicular conjunctivitis and neonatal ophthalmia in a Liverpool eye hospital, 1980-1984

In the five year period between 1980 and 1984, 2146 adults and 172 neonates suffering from acute conjunctivitis underwent laboratory investigation for Chlamydia trachomatis (CT), Adenoviruses (AV), Herpes Simplex Virus (HSV) and pathogenic bacteria. Epidemiology and clinical features are presented and discussed. CT was detected in 29 per cent of neonates with conjunctivitis. 5.6 per cent of adults and older children investigated for follicular conjunctivitis were CT positive. There was a significant female preponderance among CT positive neonates of 1.9:1 (p less than 0.02). 91 per cent of neonates and 62 per cent of adults in whom CT was detected were receiving some sort of treatment. Serotypes 7, 3, 10, 4 and 8 were responsible in decreasing order of frequency for 96 per cent of AV infections. Serotype 7 was seen for the first time in an adult age distribution. HSV was isolated in 1.3 per cent of cases in the absence of typical lid or corneal lesions. Viral infection was not detected in any neonate. Bacterial infection was a more likely cause than CT in neonates if infection had persisted longer than 5 weeks (p much less than 0.001). Neonates with Staph aureus infection tended to present earlier in the course of disease than those with Haemophilus sp or Pneumococcus (p less than 0.05).

Evaluation of a seven day course of oxytetracycline in women with chlamydial cervicitis

In an urban clinic for sexually-transmitted diseases, 270 women with cervical swabs culture positive for Chlamydia trachomatis were treated with 250 mg oxytetracycline orally four times daily for 7 days. Chlamydial infection was found again in 17 of 220 (7.3%) women examined one month after treatment, and in 12 of 113 (9.7%) women reexamined three months after treatment. Even in cases where reinfection seemed unlikely, only 177 of 198 (89%) were cured. Most post-treatment infections were not clinically apparent, and laboratory follow-up was essential for evaluation of chemotherapy.

Diagnosis of urethritis: role of polymorphonuclear leukocyte counts in gram-stained urethral smears

Polymorphonuclear leukocytes (PMNs) in the gram-stained urethral smears of 236 consecutive sexually active men without gonorrhea were analyzed quantitatively. The frequency distribution of the highest count of PMNs per high-power field (hpf) showed a count of four PMNs to be the "cut-off" point separating men with urethritis from those without urethritis. This cut-off point correlated well with the presence of Chlamydia trachomatis as well as with turbid urine. However, the PMN count in the gram-stained urethral smear was found to be more sensitive than the appearance of the urine in the diagnosis of urethritis among those with minimal symptoms and signs and not harboring C. trachomatis. This study also demonstrated a close similarity as regards clinical features and PMN count in gram-stained urethral smears between those harboring Ureaplasma urealyticum and those with no organisms.