The accuracy and efficacy of screening tests for Chlamydia trachomatis: a systematic review

External quality assessment for detection of Chlamydia trachomatis

The use of molecular methods for detection of Chlamydia trachomatis is increasing in clinical laboratories. External quality assessment enables unbiased monitoring of the performance of laboratories in the detection of specific pathogens. This study details the results of molecular and enzyme immunosorbent assay (EIA) testing for C. trachomatis detection in simulated endocervical swab specimens recently distributed internationally by United Kingdom National External Quality Assessment Scheme for Microbiology (UK NEQAS for Microbiology) external quality assessment panels. The frequency of accurate detection of C. trachomatis in the panels ranged from 32 to 100%. Participants using molecular methods were significantly more likely to detect C. trachomatis in specimens than those using an EIA. Two strains were distributed with the panels: an L2 laboratory-adapted strain and an uncharacterized primary isolate. Further analysis indicated a difference in detection of C. trachomatis between specific methods only with the L2 strain at lower concentrations. In addition, eight negative specimens were distributed, and false positives were found to be rare by all methods included in the study.

Implementation of a pilot programme for screening for chlamydial infection in general practice

OBJECTIVES

To determine whether opportunistic screening for Chlamydia trachomatis, based on a selective screening, algorithm, is possible in general practice in Belgium; to assess feasibility of the screening strategy with respect to workload, acceptability, and organisational aspects.

METHODS

Implementation of a pilot screening programme by 37 GPs for a period of 15 weeks. GPs' screening practices were registered and compared with the guidelines they had received. Outcome measures were: the number of patients included in the risk assessment, uptake of screening by eligible patients, prevalence of previously unidentified infection, and uptake of treatment. After the study period GPs evaluated a number of feasibility issues on a scoring form.

RESULTS

326 women underwent the risk assessment and 214 were tested by an amplification assay on a urine sample. Prevalence in woman at risk was 6.4%. Overall effective screening rate was 77.6%; 9 of 11 positives took up treatment. Participating GPs found the strategy feasible and perceived that it was well accepted by their patients.

DISCUSSION

The screening strategy was easily implemented by most GPs but some of them dropped out. The guidelines were followed relatively well and there were no major logistic problems. The uptake of treatment wat suboptimal. Efforts must be made to stimulate and educate more GPs to perform screening; laboratory and storage conditions should be optimised; refunding criteria should be revised; and overscreening must be avoided.

Chlamydia trachomatis infections in Greece: first prevalence study using nucleic acid amplification tests

The present retrospective study was initiated to determine the prevalence of Chlamydia trachomatis and to assess the risk factors for infection in adult women and men presenting to general practitioners, gynecologists, dermatologists, and family-planning centers in Greece. The study was carried out in four different Greek hospital centers using highly sensitive nucleic acid amplification techniques. Altogether, 16,834 women and 1,035 men were enrolled from October 1998 to April 2004. Two types of specimens were collected from each patient: cervical swabs from women, urethral swabs from men, and first-catch urine from women and men. All specimens were examined with the Cobas Amplicor C. trachomatis polymerase chain reaction assay (Roche Molecular Systems, Branchburg, NJ, USA) or the LC x C. trachomatis ligase chain reaction assay (Abbott Laboratories, Abbott Park, IL, USA). Demographic and behavioral data were collected by clinicians using a standardized questionnaire. A total of 704 (3.9%) patients were infected with C. trachomatis. The prevalence among female patients was 3.5% and that among male patients 11.2%. Among infected patients, 88% were under 30 years of age, 71% reported more than one sexual partner, and 91% reported a new sexual partner within the last year. In conclusion, the prevalence of C. trachomatis infection in Greece is low. Young age and new and multiple sexual partners within the last year were factors consistently associated with an increased risk of chlamydial infection.

Molecular genetic methods for diagnosis and characterisation of Chlamydia trachomatis and Neisseria gonorrhoeae: impact on epidemiological surveillance and interventions

One of the mainstays in the prevention of Chlamydia trachomatis and Neisseria gonorrhoeae infections is the availability of laboratory diagnostics with high sensitivity and specificity. Assays for diagnosis of C. trachomatis include cell culture and nucleic acid amplification tests (NAATs). The major target sequences for C. trachomatis diagnosis by NAATs are located at the cryptic plasmid and the major target used for characterisation is the omp1 gene. The gold standard for diagnosis of N. gonorrhoeae is culture. However, numerous NAATs for identification of N. gonorrhoeae and a number of molecular genetic methods for characterisation of N. gonorrhoeae have been developed. Probably no routine laboratory can attain as high sensitivity by culturing C. trachomatis or N. gonorrhoeae as by using NAATs. For that reason NAATs can be recommended for diagnosing C. trachomatis, but not as the only diagnostic assay for N. gonorrhoeae, due to lack of antibiotic susceptibility testing and specificity problems, most pronounced for pharyngeal and rectal samples. Genotyping of C. trachomatis or N. gonorrhoeae provides additional information for contact tracing. It is recommended for N. gonorrhoeae, at least in low prevalence geographic areas, but cannot today be recommended for C. trachomatis. This is due to the low genetic variability and hence the limited benefits for partner notification. However, genotyping of C. trachomatis may play an important role under special circumstances.

The prevalence of genital Chlamydia trachomatis in Australia 1997 - 2004: a systematic review

Objectives: To determine by systematic review the prevalence of genital chlamydial infection in Australia between 1997 and 2004. Methods: Electronic literature databases, reference lists, and conference proceedings were searched and health agencies and jurisdictions were contacted for published and unpublished reports. Studies were eligible if they offered a diagnostic nucleic acid amplification test to consecutive individuals presenting during the study period. As a summary measure of the available data, mean prevalence rates, weighted by sample size and irrespective of participant age, were calculated for the population sub-groups. Results: 40 studies of 50 populations and 40587 individuals met the inclusion criteria, but only one of these was population-based. The use of non-systematic methodologies prevented an assessment of time trends and a statistical comparison of population sub-groups. The mean overall prevalence of genital chlamydial infection was 4.6% (95% CI 4.4–4.8%), reflecting over-sampling of high-risk groups. The mean community-based rates were 7.5% (95% CI 6.4–8.6%) and 8.7% (95% CI 7.9–9.7%) for Indigenous men and women, and 1.5% (95% CI 1.1–1.9%) and 1.4% (95% CI 0.9–2.0%) for non-Indigenous men and women. The overall mean estimates for other groups were 3.3% (95% CI 3.0–3.7%) for female attendees of sexual health and related clinics, 5.6% (95% CI 4.9–6.4%) for adolescents and young adults, 3.3% (95% CI 2.8–3.9%) for sex workers, and 1.6% (95% CI 1.2–2.0%) for urethral infection in men who have sex with men. Clinic-based estimates were generally, although not consistently, higher than community-based estimates. There is no serial population-based data for sexually active young men and women, but the available age-specific rates suggest under-ascertainment by the routine surveillance systems. Conclusions: The prevalence of genital chlamydial infection in Indigenous Australians and young adults is unacceptably high and quality epidemiological studies are urgently required to supplement the routinely collected national notification data.

Comparison of the APTIMA CT and GC assays with the APTIMA combo 2 assay, the Abbott LCx assay, and direct fluorescent-antibody and culture assays for detection of Chlamydia trachomatis and Neisseria gonorrhoeae

The Gen-Probe APTIMA Combo 2 (AC2) is a Food and Drug Administration-cleared nucleic acid amplification test (NAAT) for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae from urine and urogenital swab specimens. The Centers for Disease Control and Prevention have recommended confirmation of positive NAAT results in low-prevalence populations. APTIMA CT (ACT) and APTIMA GC (AGC) are two discrete NAATs for C. trachomatis and N. gonorrhoeae detection that are suitable for confirming AC2-positive results because they target different nucleic acid sequences. Our objective was to determine if ACT and AGC could be used as confirmatory tests for AC2 and to correlate the APTIMA assays with culture, direct fluorescent-antibody (DFA), and LCx CT and GC assays. Urine and swab specimens (1,304) were initially tested with either culture, DFA, or LCx, followed by AC2. A subset (675) was then tested with ACT and AGC. There was absolute concordance between ACT-AGC and AC2. LCx did not detect 1 of 14 AC2-ACT- and 1 of 6 AC2-AGC-positive urine samples, and it yielded one C. trachomatis- and one N. gonorrhoeae-positive swab result that were not detected by AC2 and ACT-AGC. Culture failed to detect 5 of 20 AC2-ACT and 3 of 4 AC2-AGC positives, and DFA missed 4 of 4 AC2-ACT positives. Thus, ACT and AGC relative sensitivity compared to that of AC2 was 100%. All APTIMA assays detected more confirmed positive results than culture, DFA, and LCx. The performance of APTIMA assays was not altered by the use of various swab types and by long-term storage of specimens. All APTIMA assays are highly sensitive and rapid. ACT and AGC can be recommended for confirmation of positive results from other NAATs, such as AC2 and LCx.

Comparison of three nucleic acid amplification tests for detection of Chlamydia trachomatis in urine specimens

Traditionally, culture and immunoassays have been performed for the detection of sexually transmitted diseases, including Chlamydia trachomatis. However, these assays may often require invasive specimen collection methods, such as female cervical and male urethral swabs. Recently, nucleic acid amplification tests (NAATs) have been approved for testing for the presence of C. trachomatis in urine samples. Our objective was to compare the sensitivities and specificities of C. trachomatis detection in urine samples with three NAATs: the Abbott LCx (LCx), BD ProbeTec ET (ProbeTec), and Gen-Probe APTIMA Combo 2 (AC2). Urine specimens (n = 506) were collected from both symptomatic and asymptomatic males and females from various high school health clinics. Specimens were tested for C. trachomatis with the three NAATs, and a true-positive result was defined as any two positive NAATs. The C. trachomatis prevalence was 14.8% (75 of 506 samples). Of the 75 urine samples defined as true positives, LCx detected 72, ProbeTec 72, and AC2 detected 75. The sensitivities of LCx, ProbeTec, and AC2 for C. trachomatis detection were 96.0, 96.0, and 100%, and the specificities were 99.1, 100, and 98.8%, respectively. Four of five samples that were positive with AC2 and negative with LCx and ProbeTec were found to be positive with an alternative target TMA-based NAAT, APTIMA C. trachomatis, suggesting that they may have been true positives. Two of four uniquely positive LCx samples available for subsequent testing were both found to be positive by Roche PCR. We found that the LCx, ProbeTec, and AC2 NAATs are highly sensitive and specific methods for the detection of C. trachomatis in urine specimens and can be recommended for noninvasive screening of C. trachomatis in urine.

Sexually transmissible infections other than HIV

Sexually transmitted infections (STIs) are notable for their fastidious requirements for transmission and growth in the laboratory and for their high physical and psychosocial morbidity. The combination of subtle or absent symptoms and stigma preventing the seeking of health care, leaves many infections undiagnosed. The development of nucleic-acid amplification tests heralded a new era in sensitive and robust diagnostic procedures for STIs. Unfortunately, many of these tests are not commercially available or are too expensive for the populations that need them most. Single-dose oral azithromycin has improved the treatment of several bacterial STIs, but quinolones are rapidly becoming ineffective for gonorrhoea. Self-treatment of genital warts with podophyllotoxin or imiquimod preparations is attractive to patients and might be cost effective for health services. The prospect of effective vaccines against genital papillomaviruses in the near future is real. Such vaccines could reduce the global incidence of some anogenital cancers. Episodic treatment of genital herpes is getting easier and cheaper, and suppressive treatment can reduce transmission to regular sexual partners. A vaccine against herpes simplex virus type 2 has shown some limited efficacy. Ultimately, better control of STIs, and reduction of their contribution to the spread of HIV, will require a broad health-sector response with adequate resourcing, and a change in social and political attitudes.

Assessment of Chlamydia trachomatis infection of semen specimens by ligase chain reaction

Diagnostic potential of the Chlamydia trachomatis ligase chain reaction system (LCx) to assess the presence of C. trachomatis in urine and semen specimens was evaluated. Paired urine and semen specimens from 153 asymptomatic male partners of subfertile couples attending our Center for Reproductive Medicine were examined by LCx. As controls, 19 semen samples from four donors who were participating in the programme for artificial insemination were used. Of these, 12 samples had previously been shown to be C. trachomatis-positive by an in-house PCR. C. trachomatis was detected by LCx in seven of 153 (5 %) urine samples. None of the 153 semen samples tested positive by LCx. Also, none of the 12 C. trachomatis-containing control semen samples were positive by LCx. By in-house PCR, seven urine specimens and two of 153 (1 %) semen samples tested positive. The corresponding urine samples of these male partners were also C. trachomatis-positive, as well as the 12 C. trachomatis-containing samples from donors. In conclusion, LCx is not sensitive enough to assess the presence of C. trachomatis in semen specimens; therefore, this method is not recommended to routinely screen semen specimens from donors who participate in programmes for artificial insemination or male partners of subfertile couples for C. trachomatis.