Use of the polymerase chain reaction for the detection of Chlamydia trachomatis from endocervical and urine specimens in an asymptomatic low-prevalence population of women

Frequency of Chlamydia trachomatis in Ureaplasma-positive healthy women attending their first prenatal visit in a community hospital in Sapporo, Japan

BACKGROUND

Although Chlamydia trachomatis is the most commonly reported pathogen that causes urogenital infection such as urethritis or cervicitis, Ureaplasma parvum and Ureaplasma urealyticum, which are commensals in the genital tract, have also now been recognized as contributors to urogenital infection. However, whether the presence of either U. parvum or U. urealyticum is related to that of C. trachomatis in the urogenital tract remains unknown. We therefore attempted to estimate by PCR the prevalence of C. trachomatis, U. parvum and U. urealyticum in endocervical samples obtained from healthy women attending their first prenatal visit in Sapporo, Japan.

METHODS

The samples were taken from 303 apparently healthy women, and the extracted DNAs (n = 280) were used for PCR detection targeting C. trachomatis, U. parvum and U. urealyticum. Statistical analysis of the data was performed by Fisher's exact test.

RESULTS

PCR detection revealed that the prevalence of C. trachomatis, U. parvum and U. urealyticum was 14.3% (40/280), 41.7% (117/280) and 8.9% (25/280), respectively. C. trachomatis ompA genotype D was most frequently identified. Surprisingly, either C. trachomatis or Ureaplasma spp. was detected in almost half of the healthy women. Mixed infection of C. trachomatis with either U. parvum or U. urealyticum was also observed in 9.2% (26/280) of the women. There was a significant association between C. trachomatis and either U. parvum (p = 0.023) or Ureaplasma total (p = 0.013), but not U. urealyticum (p = 0.275).

CONCLUSION

This study demonstrated that the presence of Ureaplasma had a significant effect on the presence of C. trachomatis in the genital tract of healthy women, suggesting that mixed infection is an important factor in bacterial pathogenesis in the genital tract.

Reasons for testing women for genital Chlamydia trachomatis infection in the Calgary region

OBJECTIVE

To determine the clinical reason(s) for screening women with varying degrees of risk for genital Chlamydia trachomatis (CT) in the Calgary region.

DESIGN

Women aged 15 to 75 years were enrolled at various patient care locations. Pertinent risk factors for genital CT infection were recorded and a gynecological examination was performed. Two endocervical swabs and a first-void urine sample were collected for CT detection using two different nucleic acid amplification test methods.

SETTING

Calgary is an urban region that provides healthcare services to a population of almost one million people. Microbiology services are provided by Calgary Laboratory Services through a centralized regional laboratory service.

MAIN RESULTS

504 women with a mean age of 28.1 +/-SD 8.22 years were enrolled. Two hundred ninety-one women (57.8%) were at high risk for acquiring genital CT infection. Twenty-eight (5.6%) tested positive for CT infection and almost all of these women (26 of 28, 93%) had risk factors for acquiring infection. Of the high-risk women, 9.8% were CT positive versus only 1.3% of women at low risk (P=0.0001). Only two of 152 (1.3%) women older than 30 years had genital CT infections. Although most women were asymptomatic, those with laboratory-confirmed CT infection were more likely to have genitourinary symptoms. Three hundred forty-three of 476 (72%) women who did not have genital CT infection had no risk factors, and screening was done as part of a routine gynecological examination for other purposes (prenatal visit, Pap smear).

CONCLUSION

Women without risk factors are being screened routinely for genital CT infection as part of a routine gynecological examination done for other reasons. Elimination of the routine screening of low-risk women older than 30 years of age would decrease the current regional utilization of CT tests by as much as one-third.

Limitations of screening tests for the detection of Chlamydia trachomatis in asymptomatic adolescent and young adult women

OBJECTIVE

The purpose of this study was to examine the performance of different test types, specimen sources, and collection methods for screening of genital Chlamydia trachomatis infection in young women.

STUDY DESIGN

Asymptomatic women aged 16 to 25 years collected their own vaginal swabs and a first-voided urine specimen; a clinician collected urethral, vaginal, and endocervical swabs for culture and nucleic acid amplification tests, polymerase chain reaction and ligase chain reaction. A positive culture, 2 positive nucleic acid amplification tests, or 1 positive nucleic acid amplification test confirmed by a separate nested polymerase chain reaction comprised the criterion standard to define a C. trachomatis-infected woman.

RESULTS

The prevalence of C. trachomatis was 22% (30/139 women). All 9 test results were available for 126 participants (91%). Sensitivities were comparable for polymerase chain reaction and ligase chain reaction (52%-63%), except for urine polymerase chain reaction (44%), and were lower for culture (22%-37%); specificities were 99% to 100%, except for urine ligase chain reaction (91%). Positive predictive values were >93%, except for urine ligase chain reaction (65%); negative predictive values were 83% to 91%. Combining nucleic acid amplification test results from 2 different specimens improved sensitivities without compromising specificity.

CONCLUSION

When C. trachomatis infection was defined by multiple tests from different specimen sources, the sensitivity of any 1 test from a single specimen source was lower than generally reported. The limitations of the use of a single test to identify C. trachomatis infection should be considered when test type, specimen source, and collection method for screening young women is being determined.

The impact of switching to polymerase chain reaction for the diagnosis of Chlamydia trachomatis infections in women

BACKGROUND

We noted a marked increase in Chlamydia trachomatis (CT) infections in the Capital Health Region of NS coincident with substitution of a PCR for an enzyme immunoassay (EIA). We reviewed our experience to determine the cost of switching and the impact on the number of new infections diagnosed.

METHODS

Information on the number of EIA and PCR tests performed on women was retrieved from an abstracted laboratory information database. We examined records of testing performed between April 1998 and December 2001. Prior to June 2001, all genital swabs were tested using the MicroTrak, II Chlamydia EIA and confirmed by direct fluorescence examination. After July 2001, genital swabs were tested using the COBAS AMPLICOR C. trachomatis test.

RESULTS

During the study period, 62,288 EIA tests were performed on specimens submitted; 2,061 (3.33%) were positive. In the six months when testing was performed by the PCR method, 9,559 PCR tests were performed, 463 (4.84%) were positive; 46% increase. In the three years before PCR testing was implemented, an average of 1,626 specimens were submitted monthly. An average of 54 tests were positive (3.3%). The cost for each positive detected by PCR was 208 dollars Cdn and 226 dollars by EIA.

CONCLUSIONS

The switch to PCR for the diagnosis of CT produced a marked increase in the number of chlamydia infections diagnosed. The recent increase in the number of reported CT cases in Canada may be due in large part to more sensitive tests. Surprisingly, the cost of each positive test by PCR was 18 dollars Cdn less than that of the EIA.

Improved sensitivity of the Chlamydia trachomatis Cobas Amplicor assay using an optimized procedure for preparation of specimens

The aim of this study was to evaluate the performance of an improved sample preparation procedure that enhances the sensitivity of the Chlamydia trachomatis Cobas Amplicor assay (Roche, Switzerland). This procedure was developed after it was observed that, in some cases, endocervical swabs positive for Chlamydia trachomatis in a direct immunofluorescence assay were negative in the Chlamydia trachomatis Cobas Amplicor. For this procedure, the initial sample volume was increased over that recommended by the manufacturer, the sample was concentrated by centrifugation, and the yield of the extraction was increased by an additional enzymatic lysis. Five hundred sixteen endocervical swabs from women visiting a family planning clinic were tested in parallel by the Chlamydia trachomatis Cobas Amplicor using the extraction procedure recommended by the manufacturer and the modified in-house sample preparation procedure. Eight samples were positive with both procedures. Seven additional samples were positive with the in-house method only. The results show that the in-house sample preparation procedure markedly improves the test sensitivity of the Chlamydia trachomatis Cobas Amplicor assay. Consequently, the use of this improved screening protocol will facilitate the detection of even low-level infections with Chlamydia trachomatis, which in turn will lead to the introduction of earlier therapeutic interventions.

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

Screening women for lower genital tract infection with Chlamydia trachomatis is important in the prevention of pelvic inflammatory disease, ectopic pregnancy and infertility. This systematic review aims to state clearly which of the available diagnostic tests for the detection of C. trachomatis would be most effective in terms of clinical effectiveness. The review included all studies published from 1990 onward that evaluated diagnostic tests in asymptomatic, young, sexually active populations. Medline and Embase were searched electronically and key journals were hand-searched. Further studies were identified through the Internet and contact with experts in the field. All studies were reviewed by two reviewers and were scored by Irwig's assessment criteria. Additional quality assessment criteria included a documented sexual history and recording of previous chlamydial infection. The reviews were subjected to meta-analysis and meta-regression. The 30 studies that were included examined three types of DNA-based test--ligase chain reaction (LCR), PCR and gene probe--as well as enzyme immuno-assay (EIA). The results showed that while specificities were high, sensitivities varied widely across the tests and were also dependent on the specimen tested. Pooled sensitivities for LCR, PCR, gene probe and EIA on urine were 96.5%, 85.6%, 92% and 38%, respectively, while on cervical swabs the corresponding sensitivities of PCR, gene probe and EIA were 88.6%, 84% and 65%. Meta-analysis demonstrated that DNA amplification techniques performed best for both urine and swabs in low prevalence populations. We conclude that nucleic acid amplification tests used on non-invasive samples such as urine are more effective at detecting asymptomatic chlamydial infection than conventional tests, but there are few data to relate a positive result with clinical outcome.

Evaluation of sequential testing strategies using non-amplified and amplified methods for detection of Chlamydia trachomatis in endocervical and urine specimens from women

Nucleic acid amplification tests (NAAT) are more sensitive than other methods for the diagnosis of Chlamydia trachomatis (CT) genital infections. Two unique sequential testing strategies that employed two different commercial NAAT methods to detect CT in a population of women with widely varying infection risk were evaluated. Specimens from 504 women aged 15 to 75 years were studied. Two endocervical swabs and a urine sample were collected from each woman. One swab was initially tested using the Access enzyme immunoassay (EIA) (Beckman). An aliquot from the EIA extraction was subsequently amplified using the COBAS AMPLICOR CT assay (PCR) (Roche). The second swab was initially tested using the PACE 2 CT hybridization assay (Gen-Probe). An aliquot was pipetted off prior to performing the PACE 2 assay and also amplified using the AMP-CT assay (TMA) (Gen-Probe). Urine samples were tested for CT using both NAAT methods. True CT infections were defined as any woman that was confirmed to be positive on both NAAT results from endocervical swabs. The results of all other CT assays were compared against this expanded gold standard. 28 women were confirmed to have CT infection giving an overall prevalence of 5.6%; low-risk women had a rate of 1.3% while high-risk women had a rate of 9.8%. NAAT methods have a higher sensitivity for detecting CT cervicitis when swabs are tested compared to urine. The positive predictive value of NAAT is decreased when testing low risk women. Limited automation makes it difficult to test a high volume of samples (i.e., > 100 swabs and/or urines) using either of these NAAT methods and continue to provide same day results. Laboratories performing CT testing must define the female population served so that appropriate diagnostic strategies can be employed.

Relative accuracy of nucleic acid amplification tests and culture in detecting Chlamydia in asymptomatic men

Published estimates of the sensitivity and specificity of PCR and ligase chain reaction (LCR) for detecting Chlamydia trachomatis are potentially biased because of study design limitations (confirmation of test results was limited to subjects who were PCR or LCR positive but culture negative). Relative measures of test accuracy are less prone to bias in incomplete study designs. We estimated the relative sensitivity (RSN) and relative false-positive rate (RFP) for PCR and LCR versus cell culture among 1,138 asymptomatic men and evaluated the potential bias of RSN and RFP estimates. PCR and LCR testing in urine were compared to culture of urethral specimens. Discordant results (PCR or LCR positive, but culture negative) were confirmed by using a sequence including the other DNA amplification test, direct fluorescent antibody testing, and a DNA amplification test to detect chlamydial major outer membrane protein. The RSN estimates for PCR and LCR were 1.45 (95% confidence interval [CI] = 1.3 to 1.7) and 1.49 (95% CI = 1.3 to 1.7), respectively, indicating that both methods are more sensitive than culture. Very few false-positive results were found, indicating that the specificity levels of PCR, LCR, and culture are high. The potential bias in RSN and RFP estimates were <5 and <20%, respectively. The estimation of bias is based on the most likely and probably conservative parameter settings. If the sensitivity of culture is between 60 and 65%, then the true sensitivity of PCR and LCR is between 90 and 97%. Our findings indicate that PCR and LCR are significantly more sensitive than culture, while the three tests have similar specificities.

[Screening of Chlamydia trachomatis: is the diagnostic efficacy good enough?]

OBJECTIVE

In the background of discrepant results of C. trachomatis testing in women with suspected genital infections, three different tests have been compared.

METHOD

594 endocervical swabs were collected from women visiting the family planning clinic in Aarau. Each of the following tests was evaluated: Cobas Amplicor Chlamydia trachomatis, IF Chlamyset, and Chlamydia IF direct. If one of these three tests was positive, the fixed material on the slides was scraped off, and a PCR was performed.

RESULTS

15 out of 594 samples were "true'-positive. PCR recognized 14 of them, the IF Chlamyset 13, and the Chlamydia IF 8. With the IF Chlamyset 37 samples were false-positive.

CONCLUSIONS

PCR testing exhibits a good sensitivity and a high specificity, but we think that the sensitivity can be increased by improving the sample preparation step. The Chlamydia IF direct has a good specificity, but a rather low sensitivity. It should be noted that the PCR has the potential to become a new gold standard for the detection of C. trachomatis.

Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by enzyme immunoassay, culture, and three nucleic acid amplification tests

The purpose of this study was to evaluate and compare three commercially available nucleic acid amplification tests (NAATs) for the detection of Neisseria gonorrhoeae and Chlamydia trachomatis. Roche PCR and Becton Dickinson strand displacement amplification (SDA) were performed on 733 endocervical swab specimens from commercial sex workers. Abbott ligase chain reaction (LCR) was performed on a subset of 396 samples. Endocervical specimens from all women were also tested by culture for N. gonorrhoeae and by Syva MicroTrak enzyme immunoassay (EIA) for C. trachomatis. A positive N. gonorrhoeae result was defined as a positive result by culture or by two NAATs, and a positive C. trachomatis result was defined as a positive result by two tests. According to these definitions, the sensitivities and specificities for the subsample of 396 specimens of N. gonorrhoeae culture, PCR, SDA, and LCR were 69.8, 95.2, 88.9, and 88.9% and 100, 99.4, 100, and 99.1%, respectively; the sensitivities and specificities of C. trachomatis EIA, PCR, SDA, and LCR were 42.0, 98.0, 94.0, and 90.0% and 100, 98.0, 100, and 98.6%, respectively. The performance characteristics of N. gonorrhoeae culture, PCR, and SDA and C. trachomatis EIA, PCR, and SDA for all 733 specimens were defined without inclusion of LCR results and by discrepant analysis after resolution of discordant N. gonorrhoeae PCR results and of discordant C. trachomatis EIA and PCR results by LCR testing. The sensitivities of N. gonorrhoeae culture, PCR, and SDA before and after LCR resolution were 67.8, 95.7, and 93.9% and 65, 95.8, and 90.0%, respectively. The sensitivities of C. trachomatis EIA, PCR, and SDA decreased from 39.4, 100, and 100% to 38.7, 98.7, and 94.7%, respectively. All three NAATs proved to be superior to N. gonorrhoeae culture and to C. trachomatis EIA. The accuracies of the different NAATs were quite similar. SDA was the only amplification assay with 100% specificity for detection of both N. gonorrhoeae and C. trachomatis in endocervical specimens.

Screening for chlamydial infection

OBJECTIVES

To examine data on the effectiveness of screening for chlamydial infection by a physician or other health care professional. Specifically, we examine the evidence that early treatment of chlamydial infection improves health outcomes, as well as evidence of the effectiveness of screening strategies in nonpregnant women, pregnant women, and men, and the accuracy of tests used for screening. This review updates the literature since the last recommendation of the U.S. Preventive Services Task Force published in 1996.

SEARCH STRATEGY

We searched the topic of chlamydia in the MEDLINE, HealthSTAR, and Cochrane Library databases from January 1994 to July 2000, supplemented by reference lists of relevant articles and from experts in the field. Articles published prior to 1994 and research abstracts were cited if particularly important to the key questions or to the interpretation of included articles.

SELECTION CRITERIA

A single reader reviewed all English abstracts. Articles were selected for full review if they were about Chlamydia trachomatis genitourinary infections in nonpregnant women, pregnant women, or men and were relevant to key questions in the analytic framework. Investigators read the full-text version of the retrieved articles and applied additional eligibility criteria. For all topics, we excluded articles if they did not provide sufficient information to determine the methods for selecting subjects and for analyzing data.

DATA COLLECTION AND ANALYSIS

We systematically reviewed three types of studies about screening in nonpregnant women that relate to three key questions: (1) studies about the effectiveness of screening programs in reducing prevalence rates of infection, (2) studies about risk factors for chlamydial infection in women, and (3) studies about chlamydial screening tests in women. Our search found too few studies on pregnant women to systematically review, although pertinent studies are described. We systematically reviewed two types of studies about screening in men: (1) studies about prevalence rates and risk factors for chlamydial infection in men and (2) studies about chlamydial screening tests in men.

MAIN RESULTS

Nonpregnant women. The results of a randomized controlled trial conducted in a large health maintenance organization indicate that screening women selected by a set of risk factors reduces the incidence of pelvic inflammatory disease (PID) over a 1-year period. Changes in population prevalence rates have not been well documented because few studies have employed a representative population sample. Age continues to be the best predictor of chlamydial infection in women, with most studies evaluating cut-offs at age younger than 25 years. Other risk factors may be useful predictors, but these are likely to be population specific. To determine the accuracy of screening tests for women, we retrieved and critically reviewed 34 articles on test performance. Results indicate that endocervical swab specimens and first-void urine specimens have similar performance when using DNA amplification tests and have better sensitivity than endocervical culture. Recurrent chlamydial infections in women have been associated with increased risks for PID and ectopic pregnancies. Pregnant women. The Second Task Force recommendations for screening pregnant women were based on two major studies demonstrating improved pregnancy outcomes following treatment of chlamydial infection. We identified no recent studies on this topic in our literature search. Very few studies describe risk factors for chlamydial infection in pregnant women. Nonculture testing techniques appear to perform well in pregnant women, although studies are limited. Men. No studies described the effectiveness of screening or early treatment for men in reducing transmission to women or in preventing acute infections or complications in men. Studies of prevalence rates and risk factors for chlamydial infection in men are limited. Age lower than 25 years is the strongest known risk factor cited so far. Results of urethral swab specimens compared to first-void urine specimens were similar for DNA amplification tests. DNA amplification techniques are more sensitive than culture.

CONCLUSIONS

Screening women for Chlamydia trachomatis reduces the incidence of PID, and it is associated with reductions in prevalence of infection in uncontrolled studies. No studies were found to determine whether screening asymptomatic men would reduce transmission or prevent acute infections or complications. Age is the strongest risk factor for men and women. A variety of tests can detect chlamydial infection with acceptable sensitivity and specificity, including new DNA amplification tests that use either endocervical swabs in women, urethral swabs in men, or first-void urine specimens from men and women.

Chlamydia trachomatis and human papillomavirus infection in Indian women with sexually transmitted diseases and cervical precancerous and cancerous lesions

OBJECTIVES

Sexually transmitted diseases (STDs) and anogenital cancers are the major health problems in Indian women but no reliable estimate of the prevalence of either genital chlamydial infection or human papillomavirus (HPV) infection in STD patients is available. The aim of this study was to detect the frequency of Chlamydia trachomatis and the most prevalent high-risk HPV type 16 (HPV 16) infection in Indian women, with STDs and precancerous and cancerous lesions of the uterine cervix by polymerase chain reaction (PCR), and their comparison with those of conventional serology and antigen tests used for C. trachomatis detection.

METHODS

Endocervical swabs or scrapes were collected from 50 women with STDs and 30 normal healthy women attending the STD clinics of Smt. Sucheta Kripalani Hospital, New Delhi. Scraped cervical cell specimens were also collected from 50 women with precancerous and cancerous lesions of the uterine cervix. Detection of C. trachomatis and HPV was carried out by PCR using chlamydia and HPV genome-specific oligonucleotide primers. The detection of chlamydial antigen and IgG-specific antibodies was carried out by enzyme immunoassay (EIA) and serological enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

A chlamydia plasmid-based PCR assay detected 50% (25 of 50) positivity of C. trachomatis in STD patients and HPV 16 DNA was found in 30% (15 of 50) of these cases which are significantly higher than those found in healthy controls. The PCR estimate of chlamydia was found to be higher than its reported frequency by tissue culture. The EIA could detect chlamydial antigen in only 13 cases (26%) while serological ELISA revealed evidence of chlamydia IgG-specific antibodies in 26 (52%) cases. Interestingly, in women with precancerous and cancerous lesions, the rate of HPV 16 infection was very high (52% and 72%, respectively), whereas the frequency of chlamydia infection was found to be 12-22% only. Occurrence of other sexually transmitted agents was also evaluated in the women.

CONCLUSIONS

This is the first PCR estimate of genital chlamydial (50%) and HPV 16 (30%) infection in STD patients and women with precancerous and cancerous lesions of the uterine cervix in India. The PCR method seems to be a good alternative to tissue culture.

An algorithm to detect Chlamydia trachomatis by polymerase chain reaction on specimens extracted for enzyme immunoassay

Amplification assays for detecting Chlamydia trachomatis have been shown to be more sensitive than enzyme immunoassay (EIA) by many investigators. In this study, we have developed an algorithm for performing PCR (COBAS AMPLICOR) on selected specimens extracted for EIA (ACCESS) with sample-to-cutoff (s/co) values between 0.25 and 0.99. Furthermore, we have shown that these specimens can be utilized for PCR without encountering any inhibition problems. In our investigation, 230 out of 6,558 urethral and cervical swabs submitted for C. trachomatis screening by EIA over a period of 9 months, had s/co values ranging between of 0.25 and 0.99. Ninety (39.1%) of these specimens tested positive by PCR. These specimens were stable and gave reproducible PCR results before and after storage for a period of 9 months. This testing algorithm offers an effective way of detecting C. trachomatis with selective use of PCR while increasing the sensitivity of the EIA screening system.

Rapid assessment of sexually transmitted diseases in a sentinel population in Thailand: prevalence of chlamydial infection, gonorrhoea, and syphilis among pregnant women--1996

OBJECTIVE

To determine the prevalence of sexually transmitted diseases (STDs) among pregnant women in Thailand, where case reporting suggests a marked decrease in STDs following a campaign promoting condom use during commercial sex.

DESIGN

Cross sectional study of women at their first visit to the study hospitals' antenatal clinics in Chiang Rai (n = 500) and Bangkok (n = 521).

METHODS

First catch urine specimens were tested for Chlamydia trachomatis and Neisseria gonorrhoeae using the Amplicor CT/NG polymerase chain reaction assay. Syphilis and HIV serological testing were performed in the study hospitals' laboratories.

RESULTS

The prevalence of chlamydial infection was 5.7%, gonorrhoea 0.2%, and syphilis 0.5% (all VDRL or RPR titres were < or = 1:4). The prevalence of HIV infection was 7.1% in Chiang Rai and 2.9% in Bangkok. In a multivariate logistic regression analysis, chlamydial infection was associated with younger age and with higher gestational age at first antenatal clinic visit, but was not associated with marital status, gravidity, city of enrollment, or HIV infection status.

CONCLUSIONS

There was a low prevalence of gonorrhoea and syphilis among these pregnant women in Thailand. Chlamydial infection was detected at a higher prevalence, especially among younger women and women registering later for antenatal care. Testing of pregnant women using easily collected urine specimens and a sensitive nucleic acid amplification assay is a feasible method of rapidly assessing chlamydial and gonococcal prevalence.

Detection of Chlamydia trachomatis cervical infection by urine tests among adolescents clinics

PURPOSE

To compare urine ligase and polymerase chain reaction (LCR, PCR) tests for diagnosis of Chlamydia trachomatis cervical infection with PCR and nucleic acid probe (GPA) on cervical specimens in adolescents, as well as risk factors for C. trachomatis infection and prevalence of infection at enrollment.

METHODS

Urine and cervical specimens were collected from women aged 13-20 years attending adolescent clinics, and interviews were administered. Urine specimens were tested by PCR and LCR, and cervical specimens by GPA and PCR. Prevalence rates of C. trachomatis infection and gonorrhea were compared by demographic, behavioral, and clinical risk factors.

RESULTS

Of 415 women tested, 86 (20.7%) were infected with C. trachomatis as indicated by positive cervical PCR results. A higher prevalence of C. trachomatis infection was seen among adolescents who douched monthly or more frequently, or had gonorrhea; prevalence declined from 25.8% in the first 7 months to 16.3% in the last 14 months of the study (p = .017). A statistically significant protective effect for reported condom use was not observed. Sensitivity of urine PCR was 89.5% and specificity was 100% relative to cervical PCR, compared to 84.9% and 99.4% (urine LCR) and 65.4% and 98.0% (cervical GPA). Sensitivity of urine PCR was higher in women with discharge; urine LCR sensitivity was higher in women < 19 years of age.

CONCLUSIONS

Polymerase chain reaction and LCR assays on urine specimens were sensitive, specific, and noninvasive tests in this population of adolescents with high C. trachomatis infection prevalence. Chlamydia trachomatis infection was associated with douching monthly or more frequently. Prevalence of infection declined over the period during which the study was conducted.

Evaluation of bias in diagnostic-test sensitivity and specificity estimates computed by discrepant analysis

When a new diagnostic test is potentially more sensitive than the reference test used to classify persons as infected or uninfected, a substantial number of specimens from infected persons may be reference-test negative but new-test positive. Discrepant analysis involves the performance of one or more additional tests with these specimens, reclassification as infected those persons for whom the new-test-positive results are confirmed, and recalculation of the estimates of new-test sensitivity and specificity by using the revised classification. This approach has been criticized because of the bias introduced by the selective use of confirmation testing. Under conditions appropriate for evaluating a nucleic acid amplification (NAA) test for Chlamydia trachomatis infection with cell culture as the reference test, we compared the bias in estimates based on the discrepant-analysis classification of persons as infected or uninfected with that in estimates based on the culture classification. We concluded that the bias in estimates of NAA-test specificity based on discrepant analysis is small and generally less than that in estimates based on culture. However, the accuracy of discrepant-analysis-based estimates of NAA-test sensitivity depends critically on whether culture specificity is equal to or is slightly less than 100%, and it is affected by competing biases that are not fully taken into account by discrepant analysis.

Screening women for chlamydia trachomatis in family planning clinics: the cost-effectiveness of DNA amplification assays

BACKGROUND

Highly sensitive and specific DNA amplification assays are available for use on cervical and urine specimens. These new tests have the potential to identify more chlamydial infections than the commonly used enzyme immunoassay and DNA probe tests, yet they are more expensive. This study sought to assess the cost effectiveness of cell culture, enzyme immunoassay (EIA), DNA probe (Pace 2), polymerase chain reaction (PCR) of cervical and urine specimens, and ligase chain reaction (LCR) of cervical and urine specimens as screening tools for Chlamydia trachomatis in asymptomatic women younger than 30 years of age attending family planning clinics.

STUDY DESIGN

Program costs; medical cost savings of prevented sequelae in women, male sex partners, and infant; and number of prevented cases of pelvic inflammatory disease (PID), neonatal infections, and male sex partner urethritis and epididymitis were modeled in a decision analysis conducted from a health care system perspective. Results are expressed for a cohort of 18,000 women.

RESULTS

If no screening for C. trachomatis were conducted in Maryland, 497 cases of PID would develop, costing $2.2 million in future medical costs. Use of EIA to detect chlamydial infection would prevent 240 cases of PID and save $887,000 over no screening. Alternatively, use of DNA amplification assays on urine specimens would prevent up to an additional 66 cases and save $287,100 over EIA. Use of LCR on cervical specimens would prevent at least 13 additional cases of PID over the urine-based assays, but would cost $3,005 for each additional case prevented. In women receiving routine pelvic examinations, LCR of cervical specimens would prevent the most disease and provide the highest cost savings. In women not receiving routine pelvic examinations, use of LCR on cervical specimens would prevent the most disease but would cost approximately $28,000 per additional case of PID prevented over DNA amplification of urine.

CONCLUSIONS

Compared with EIA screening, the strategy with the lowest program costs, a screening strategy that combines use of DNA amplification on cervical specimens in women receiving pelvic examinations, and DNA amplification of urine in women with no medical indications necessitating a pelvic examination, prevents the most cases of PID and provides the highest cost savings. With enhanced sensitivity over the other diagnostic assays and with the use of noninvasive specimen collection, DNA amplification assays should be implemented as cost-effective components of a screening program for C. trachomatis.

Evaluation of 2-SP transport medium for detection of Chlamydia trachomatis and Neisseria gonorrhoeae by two automated amplification systems and culture for chlamydia

AIMS

To assess the performance of 2-sucrose-phosphate based transport medium (2-SP) for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae by an automated commercial polymerase chain reaction (PCR) and ligase chain reaction (LCR) compared to centrifugation culture on McCoy cells for C trachomatis. Second, to compare both amplification systems for initial diagnostic testing of a low prevalence population for sexually transmitted diseases.

METHODS

Four hundred and eighty one consecutive urogenital and conjunctival specimens were examined. All tests were performed on the same specimen collected with a dacron swab and transported in 2-SP medium. Samples that were positive by culture or by both PCR and LCR were considered to be true positives.

RESULTS

The prevalences of C trachomatis and of N gonorrhoeae were 2.7% and 0.4%, respectively. PCR had a resolved sensitivity and specificity of 100% and 99.8%, respectively, for C trachomatis, and 100% and 98.9%, respectively, for N gonorrhoeae. LCR was 100% sensitive and specific for both pathogens. The resolved sensitivity of the shell vial assay was 85%. No culture positive sample would have been missed by PCR or LCR. The inhibition rate for PCR was 4.8%.

CONCLUSIONS

2-SP medium proved to be suitable for both PCR and LCR. It is not limited to any one test manufacturer and allows the performance of amplification techniques and viral and chlamydia culture from the same specimen. The LCR was more reliable than PCR on initial testing. However, hands on time is longer, and no amplification control is available for LCR.

Multiplex AMPLICOR PCR screening for Chlamydia trachomatis and Neisseria gonorrhoeae in women attenting non-sexually transmitted disease clinics. The European Chlamydia Epidemiology Group

A new PCR kit (AMPLICOR CT/NG; Roche Diagnostic Systems, Inc., Branchburg, N.J.) was used as a screening tool for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in first-void urine (FVU) specimens from 3,340 asymptomatic women attending European health care units for contraceptive advice or pregnancy termination. All samples were kept frozen (-20 degrees C) prior to testing. Chlamydia-positive samples were retested once by the plasmid-based PCR kit and also by a major outer membrane protein (MOMP) primer-based PCR. Discrepancies were resolved by using the direct immunofluorescence test (DIF) with the centrifuged sediment of the FVU specimens. Samples positive for N. gonorrhoeae were retested by chromosomal primer-based PCR and verified by a 16S RNA PCR. Of the samples tested, 1.8% were considered inhibitory by using the internal amplification control. Of 81 samples positive for C. trachomatis, 74 samples were positive by both plasmid- and MOMP-based PCRs, 6 samples were positive by plasmid-based PCR and DIF, and one sample was positive by both MOMP-based PCR and DIF. Nine samples (0.3%) were positive for N. gonorrhoeae by the chromosomal primer-based PCR; however, none of the results could be confirmed. The test offers the unique ability to identify inhibition of amplification with the optional internal control.

Lowering the cut off value of an automated chlamydia enzyme immunoassay and confirmation by PCR and direct immunofluorescent antibody test

AIMS

To increase the sensitivity of an automated chlamydia enzyme immunoassay by significantly lowering its cut off value, and to maintain specificity by confirmation with polymerase chain reaction (PCR) and direct immunofluorescent antibody test (DFA).

METHODS

Over five months, the cut off value of the enzyme immunoassay used to screen urogenital samples for chlamydia antigen was reduced from 80 to 10. Samples with a test value of 10 or above were further tested with a commercial PCR assay. All samples during the first three months and discrepant samples during the last two months of the study were also tested with the DFA.

RESULTS

3250 urogenital swabs (1246 urethral, 1335 endocervical, 669 pooled urethral/endocervical) from 1246 males and 2004 females were processed. Using the manufacturer's recommended cut off of 80, the enzyme immunoassay identified chlamydia antigen in 134 samples (4.1%). Using the lower cut off value of 10 and either PCR or DFA as the confirmatory test, Chlamydia trachomatis was identified in 178 samples (5.5%). Thus, 45 additional positive samples were identified and the confirmed detection rate was increased by 33.8% (45/133). Excluding equivocal PCR results, the concordance between DFA and PCR was 91.8%. This strategy increased the detection rate by 2.1% in men and 0.9% in women (significant only in men). In female patients, pooled urethral/endocervical swabs as a specimen gave a significantly higher yield than endocervical swabs regardless of whether the lower cut off strategy was used.

CONCLUSIONS

This strategy of significantly lowering the cut off test value with confirmation on the same specimen by either PCR or DFA is feasible and cost effective. The use of pooled urethral/ endocervical specimens in females should be considered routinely as detection rate was significantly improved.

High prevalence of Chlamydia trachomatis infections in adolescent females not having pelvic examinations: utility of PCR-based urine screening in urban adolescent clinic setting

PURPOSE

To determine utility of polymerase chain reaction (PCR)-based urine screening for Chlamydia trachomatis in the care of adolescent females in an urban clinic.

METHODS

Females > or = 15 years of age attending an adolescent clinic were approached consecutively. Each enrollee was interviewed to determine the primary reason(s) for the clinic visit and was queried about genitourinary symptoms. Nonsterile voided urine specimens were tested for C. trachomatis using PCR-based analysis. Endocervical C. trachomatis cultures were obtained from the subjects who had a pelvic examination. Main outcome measures were chlamydia infection rates in clinic attendees whether a pelvic examination was performed or not.

RESULTS

A total of 315 (99.4%) of 317 patients approached agreed to participate. Overall, 47 (14.9%) patients had positive urine PCR tests. The chlamydia infection rate detected by urine PCR was 22.1% (19 of 86) among those who had pelvic examinations performed and 12.2% (28 of 229) among those who did not (p = .03; odds ratio 2.04; 95% confidence interval 1.02, 4.06). Sixty percent (28 of 47) of chlamydia infections identified during the study period were identified by the urine screening test.

CONCLUSION

Urine screening was accepted by vast majority of female adolescents attending the clinic irrespective of reason for the clinic visit, and was highly effective in identifying unsuspected C. trachomatis infections, particularly among girls attending the clinic for reasons unrelated to reproductive health care and as an interim screening tool for adolescent family-planning clients.

Urinary inhibitors of polymerase chain reaction and ligase chain reaction and testing of multiple specimens may contribute to lower assay sensitivities for diagnosing Chlamydia trachomatis infected women

In a comparison of commercial ligase chain reaction (LCR; Abbott) and polymerase chain reaction (PCR; Roche) assays, measuring plasmid genes of Chlamydia trachomatis, some specimens were found to be negative by either or both assays but positive in traditional culture or antigen detection tests. Of 767 women, 35 were found to be infected by cervical or urine testing. Twenty three specimens from 16 women may have contained inhibitors in six cervical swabs (CS) and 15 first void urines (FVU). By performing dilution and 'spiking' experiments on five FVU, inhibitors of PCR, LCR or both, which disappeared by dilution, were demonstrated. Confirmatory assays were used which amplified segments of the major outer membrane gene by PCR or LCR. When comparisons of assays were made on a single specimen type, the sensitivities of the amplification assays, compared to an expanded reference standard, were as follows: on CS, PCR was 93.8% (30/32) and LCR was 96.9% (31/32); on FVU, PCR was 76.6% (23/30) and LCR was 93.3% (28/30). When a combined calculation was made to determine the ability of the assays to detect patients infected in the cervix or urethra by testing FVU, the sensitivities dropped to 71.4% (25/35) for PCR and 80.0% (28/35) for LCR: CS sensitivity was 88.6% (31/35) for both amplified tests. There were two CS and five FVU false-positives by PCR which reduced to one CS and three FVU in the combined analysis. There were no false-positives by LCR. Inhibitors and low levels of chlamydial plasmid nucleic acids may have contributed to lower than expected sensitivities, suggesting a possible need for internal positive controls, especially for PCR, when testing urine. More studies with multiple sampling and more than one amplification assay are needed to confirm these findings and to identify and remove inhibitors of amplification assays.

A community-based approach to the control of sexually transmitted diseases in the Northern Territory

A program to control sexually transmitted diseases (STDs) was undertaken during a Men's Health Week in a remote Aboriginal community in Western Arnhem Land, Northern Territory. A total of 151 men aged 13 years and over who attended over a five-day period underwent a full physical examination, and first-void urine specimens were tested for the presence of leukocytes, chlamydia (by enzyme immunoassay antigen detection) and gonorrhoea (by culture and antigen detection). Blood was taken for syphilis serology from all patients and for human immunodeficiency virus (HIV) from patients with a proven STD or at the patient's request. Consent for testing was obtained from all participants. Patients with a positive urinary leukocyte test or symptoms were offered urethral swab investigations and treated empirically according to a set protocol. Patients with STDs detected by subsequent laboratory investigations were followed up and treated. The overall prevalence of one or more of syphilis, gonorrhoea or chlamydia was 17.4 per cent. No men presented with genitourinary symptoms and none was HIV-infected. In this population, STDs were an important cause of morbidity, and a community-based approach was adopted to identify infected persons. The use of urine for the detection of gonorrhoea and chlamydia was highly acceptable. Although not used in this study, polymerase chain reaction and ligase chain reaction technology will facilitate similar activities in the future.

Evaluation of the Gen-Probe Chlamydia trachomatis transcription-mediated amplification assay with urine specimens from women

We evaluated the Gen-Probe Chlamydia trachomatis transcription-mediated amplification (TMA) assay with urine specimens for the detection of C. trachomatis infections in women. The novel test, based on the isothermal amplification of chlamydial RNA, was compared with the Roche Amplicor PCR with urine and cell culture with endocervical specimens. First-catch urine and endocervical swab specimens were collected from a total of 561 patients, of whom 70 (12.3%) were confirmed to have chlamydial infection. The diagnostic sensitivity and specificity of TMA with urine were 91.4 and 99.6%, respectively, and those of Amplicor PCR were 97.1 and 99.8%, respectively. By repeated analysis of the specimens with discrepant results, the sensitivity of TMA could be increased to 99%, indicating that some methodological improvements in the assay are still to be expected. The sensitivity of PCR could be increased to 100% by the elimination of DNA polymerase inhibitors in a repeated analysis. The sensitivity and specificity of cell culture with cervical specimens were 85.7 and 100%, respectively. The results indicate that TMA with urine specimens from women is a sensitive and specific assay for the detection of C. trachomatis, providing a new noninvasive technique for the screening of chlamydial infections in women.

Comparison of manual Amplicor PCR, Cobas Amplicor PCR, and LCx assays for detection of Chlamydia trachomatis infection in women by using urine specimens

We compared the Roche Amplicor PCR, Roche Cobas Amplicor PCR, and Abbott LCx assays by using urine specimens for the detection of Chlamydia trachomatis infections in a female population. First-catch urine and endocervical swab specimens were collected from a total of 442 patients. Urine specimens were tested by the manual Roche Amplicor PCR, the automatic Roche Cobas Amplicor PCR, and the Abbott LCx assays as instructed by the manufacturers. For the Cobas Amplicor PCR, the internal control protocol was used for every specimen to reveal the presence of polymerase inhibitors. Cell culture of cervical specimens was used as a reference method. Of 442 patients, 50 (11.3%) were confirmed to have chlamydial infection. The diagnostic sensitivity and specificity of cell culture with cervical swab specimens were 88 and 100%, respectively. With urine specimens the sensitivity and specificity for the manual Amplicor PCR assay were 100 and 99.7%, respectively; those for the automatic Cobas Amplicor PCR assay were 94 and 99.2%, respectively; and those for the LCx assay were 94 and 100%, respectively. Thus, all amplification methods with urine specimens proved to be highly sensitive and specific for the detection of C. trachomatis infection in women. No statistically significant differences in the test performances could be demonstrated for specimens from this population. All three amplification techniques with urine specimens proved to be superior to cell culture with cervical swab specimens in diagnosing C. trachomatis infections in women.

Current methods of laboratory diagnosis of Chlamydia trachomatis infections

Infections caused by Chlamydia trachomatis are probably the most common sexually transmitted diseases in the United States. Commonly unrecognized and often inadequately treated, chlamydial infections can ascend the reproductive tract and cause pelvic inflammatory disease, which often results in the devastating consequences of infertility, ectopic pregnancy, or chronic pelvic pain. C. trachomatis infections are also known to increase the risk for human immunodeficiency virus infection. The obligate intracellular life cycle of C. trachomatis has traditionally required laboratory diagnostic tests that are technically demanding, labor-intensive, expensive, and difficult to access. In spite of these historical challenges, however, laboratory diagnosis of C. trachomatis has been a rapidly advancing area in which there is presently a wide array of commercial diagnostic technologies, costs, manufacturers. This review describes and compares the diagnostic methods for C. trachomatis infection that are currently approved for use in the United States, including the newest DNA amplification technologies which are yet to be licensed for commercial use. Issues to consider in selecting a test for purposes of screening versus diagnosis based on prevalence, performance, legal, social, and cost issues are also discussed.

Detection of PCR inhibitors in cervical specimens by using the AMPLICOR Chlamydia trachomatis assay

To determine that susceptibility of AMPLICOR Chlamydia trachomatis PCR to inhibitory factors possibly present in cervical specimens, we obtained cervical specimens from 200 gynecology patients attending our outpatient clinic. The prevalence of C. trachomatis infection was 4.1%, as determined by cell culture. All AMPLICOR specimens were tested in one procedure as described by the manufacturer, and after the specimen was spiked with C. trachomatis, several other pretreatment protocols were used. Complete inhibition of the PCR was observed in 38 (19%) cervical specimens. Heat treatment at 95 degrees C, freeze-thawing, or 10-fold dilution of the samples reduced the initial inhibition to 9, 16, or 9%, respectively. A combination of heat treatment and 10-fold dilution reduced the inhibition to 4% of the samples. A second specimen type (swabs inoculated in 0.2 M sucrose phosphate buffer [2SP]) was also evaluated. A 10-fold dilution of the spiked 2SP specimen resulted in an inhibition rate of 6%, which was comparable to that obtained by centrifugation of the 2SP specimen prior to processing. Furthermore, it was shown that the inhibition was not correlated with blood contamination. Processing the specimens on the day of collection or the day after resulted in a higher inhibition rate than did delayed processing (27.6 versus 15.5%, respectively). An inverse correlation was found between the concentration of C. trachomatis added to the sample and the rate of inhibition observed. The inhibition was partly correlated with the pH of the cervical mucosa. Decreased inhibition was found at pH values of > or = 7.5. The effects of blood, pH, and delay in processing were all evaluated by using the AMPLICOR specimen. We conclude that the susceptibility of AMPLICOR C. trachomatis PCR to inhibiting factors in cervical specimens can be significantly reduced if the pretreatment procedure includes heat treatment or the use of 2SP transport medium. Also, a 10-fold dilution of the clinical specimen followed by heat treatment will largely prevent the inhibition of this PCR.

A tale of two sexually transmitted diseases. Prevalences and predictors of chlamydia and gonorrhea in women attending Colorado family planning clinics

BACKGROUND

The comparative prevalences and predictors of chlamydia and gonorrhea have not been studied in the family planning clinic population.

GOALS

To determine the comparative prevalences and predictors of chlamydia and gonorrhea among Colorado family planning clinic patients.

STUDY DESIGN

Cross-sectional study of public and private family planning clinic patients in Colorado tested for both chlamydia and gonorrhea (n = 12,926).

RESULTS

Among women tested for both infections, the chlamydia prevalence rate was 4.5% and the gonorrhea prevalence rate was 0.5%. Multivariate analysis showed that independent predictors of chlamydia were age younger than 25 years, black or Hispanic race-ethnicity, cervical friability, mucopus, exposure to a sex partner with chlamydia, or multiple recent sex partners. Independent predictors of gonorrhea were age younger than 20 years, black or Hispanic race-ethnicity, or exposure to a sex partner with gonorrhea; adjusted odds ratios for exposure to gonorrhea and black race were the highest for either infection.

CONCLUSIONS

The gonorrhea prevalence rate was very low compared to that of chlamydia in patients at Colorado family planning clinics. Cost-effective gonorrhea testing strategies are needed for this population.

Diagnosis of Chlamydia trachomatis infections in asymptomatic men and women by PCR assay

A PCR assay was evaluated for its ability to detect genital chlamydial infection in asymptomatic men and women. Urethral swab specimens were collected from 472 men for culture and PCR assay, and first-void urine (FVU) specimens were collected from 379 of these men for enzyme immunoassay (EIA) and PCR assay. Cervical swab specimens were collected from 242 women for culture, EIA, and PCR assay. Patients were considered infected if they were culture positive or positive by PCR with both plasmid- and major outer membrane protein-based primers. By using this extended "gold standard," the prevalence of infection in this population was 7.6% for men and 7.9% for women. For men, the sensitivities of urethral swab specimen culture and PCR and FVU specimen EIA and PCR were 61, 72, 55, and 91%, respectively. All assays had specificities of > or = 99.8%. The positive and negative predictive values for PCR testing of FVU specimens were 100 and 99.4%, respectively, compared with values of 96.3 and 97.8%, respectively, for PCR of urethral swab specimens. The sensitivities of cervical swab specimen culture and PCR testing were 42 and 90%, respectively, with corresponding specificities of 100 and 99.3%. All cervical swabs were negative by EIA. Molecular techniques such as PCR assays are valuable tools for the detection of symptomatic genital chlamydial infection. In particular, PCR assays of FVU specimens from men offer a highly sensitive, noninvasive screening tool that will likely improve patient compliance for diagnostic testing.

Detection of Chlamydia trachomatis infections in women by Amplicor PCR: comparison of diagnostic performance with urine and cervical specimens

We used the Roche Amplicor PCR assay to compare urine and cervical swabs as sample material in the detection of Chlamydia trachomatis causing genital infections. The diagnostic performance of Amplicor PCR was compared with that of cell culture and the Gen-Probe PACE 2 assay with cervical specimens. If discrepant from other results, the specimens negative by PCR were diluted and reanalyzed to reveal PCR inhibitors. Of 666 patients, 39 (5.9%) were confirmed to have chlamydial infection. The respective sensitivity and specificity of Amplicor PCR were as follows: urine specimens, 82.0 and 99.7%; cervical specimens, 82.0 and 99.8%. Those for cell culture with cervical specimens were 84.6 and 100%. For the Gen-Probe PACE 2 assay, the sensitivity and specificity with cervical specimens were 79.5 and 100%, respectively. Without the effect of PCR inhibitors, the sensitivity of PCR with urine would have been 97.4%. Provided that the problems currently caused by inhibitors will be solved, the Amplicor PCR assay with urine specimens offers a tempting alternative for the diagnosis of C. trachomatis infection in women.

Improved PCR detection of Chlamydia trachomatis by using an altered method of specimen transport and high-quality endocervical specimens

Duplicate endocervical swabs were collected for detection of Chlamydia trachomatis by PCR (Roche Diagnostics). One swab was swirled in Specimen Transport Medium (Roche) for PCR testing and discarded. A saline aliquot from the other specimen, sent as a dry swab to the laboratory, was Papanicolaou stained to determine specimen adequacy, and the remainder was PCR tested. Significantly more (24%) PCR-positive results (118 versus 95; P < 0.001) were obtained with the dry specimens than with the swirled specimens when first tested. In addition, PCR-positive results were obtained with 107 (10.6%) of 1,007 microscopically adequate specimens but with only 3 (0.9%) of 341 inadequate specimens (P < 0.001).