Evaluation of the Abbott LCx Ligase Chain Reaction Assay for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in Urine and Genital Swab Specimens from a Sexually Transmitted Disease Clinic Population

The Abbott LCx ligase chain reaction (LCR) assay for the simultaneous detection of Chlamydia trachomatis and Neisseria gonorrhoeae was evaluated by using swab and urine specimens from 562 patients. C. trachomatis results by LCR were compared to those by the Gen-Probe PACE 2 assay, whereas N. gonorrhoeae results by LCR were compared to those by culture. The Gen-Probe and LCR assays were performed according to the manufacturers’ instructions. Gram-negative diplococci growing on modified Thayer-Martin medium were confirmed as N. gonorrhoeae by the GonoGen II assay. Supplemental data analysis was performed by major outer membrane protein PCR for C. trachomatis and probes for pilin gene detection for N. gonorrhoeae. A true-positive result for each pathogen was defined as a positive result for all three or two of three assays. Overall agreement among the six assays was 94.8%. C. trachomatis prevalence was 16.2%; N. gonorrhoeae prevalence was 5.5%. The overall sensitivity and specificity, respectively, for each test (after supplemental data analysis) were as follows: for C. trachomatis, Gen-Probe, 65.9 and 100%; LCR on urine, 90.1 and 100%; LCR on swab specimens, 96.7 and 100%; and for N. gonorrhoeae, culture, 80.6 and 100%; LCR on urine, 93.5 and 99.8%; and LCR on swab specimens, 96.8 and 100%. For women, the N. gonorrhoeae culture was very insensitive compared to its performance in men (58.3 versus 94.7%, respectively). For C. trachomatis, the Gen-Probe assay’s sensitivity was lower for men than for women (62.3 versus 71.1%, respectively). The sensitivity for C. trachomatis detection by LCR on urethral and cervical swab specimens was 96.2 and 97.4% for men and women, respectively. For men, swab results were slightly better than urine results for both pathogens (sensitivity for C. trachomatis in swab and urine specimens, 96.2 and 92.5%, respectively; sensitivity for N. gonorrhoeae in swab and urine specimens, 100 and 94.7%, respectively), while for women, cervical swabs were superior in sensitivity to urine samples for detecting C. trachomatis (swab, 97.4%; urine, 81.6%) and equivalent for N. gonorrhoeae (swab, 92.3%; urine, 91.6%). The LCx LCR appears to be both sensitive and specific for the detection of C. trachomatis and N. gonorrhoeae when performed on urine or genital swab samples. Swab samples had better sensitivity than urine samples for the detection of both pathogens.     

Comparison of Performances of Two Commercially Available Tests, a PCR Assay and a Ligase Chain Reaction Test, in Detection of Urogenital Chlamydia trachomatis Infection

The diagnostic performance of a PCR test (Roche Cobas Amplicor CT/NG Test) and that of a ligase chain reaction (LCR) test (Abbott LCx Chlamydia trachomatis assay) were compared by using endocervical and urethral swab specimen culture as a reference test. First-void urine (FVU) and endocervical and urethral swab specimens were collected from 1,015 unselected patients attending a sexually transmitted disease clinic and a clinic for adolescents in Helsinki, Finland. Chlamydia trachomatis was cultured from samples from the endocervix or urethra. PCR was performed with fresh and frozen urine and the culture transport medium. LCR was performed with fresh and frozen urine and LCx swab transport medium. Diagnostic consistency and diagnostic accuracy were statistically tested. The test results were identical for 984 patients (97%). Discrepant results were observed for 31 patients. Overall, LCR and PCR showed excellent kappa coefficients of consistency for both swab and FVU specimens (0.93 and 0.95, respectively). Sixty-one patients (6%) were culture positive. Testing of FVU by LCR or PCR increased the overall positivity rates to 7.0 and 7.7%, respectively. While PCR of FVU detected the greatest number of C. trachomatis infections (sensitivity, 96.1%), for some PCR-positive FVU specimens the results could not be confirmed (specificity, 99.6%). PCR and LCR were more sensitive than culture (sensitivities, 92 and 93% versus 79% for culture) in the diagnosis of genital C. trachomatis infection. In conclusion, both tests can be recommended for use in the clinical laboratory and for the screening of asymptomatic C. trachomatis infections.     

Use of Ligase Chain Reaction with Urine versus Cervical Culture for Detection of Chlamydia trachomatis in an Asymptomatic Military Population of Pregnant and Nonpregnant Females Attending Papanicolaou Smear Clinics

Ligase chain reaction (LCR) (Abbott Laboratories, Abbott Park, Ill.) with first-catch urine specimens was used to detect Chlamydia trachomatis infections in 465 asymptomatic military women attending clinics for routine Papanicolaou smear tests. Results were compared to results of cervical culture to determine the sensitivity of the urine LCR and the possible presence of inhibitors of amplification in pregnant and nonpregnant women. Discrepant results for LCR and culture were resolved by direct fluorescent antibody staining of culture sediments, two different PCR assays, and LCR for the outer membrane protein 1 gene. The prevalence of Chlamydia in specimens by urine LCR was 7.3% compared to 5% by culture. For 434 women with matching specimens, there were 11 more specimens positive by LCR than were positive by culture, of which all but one were determined to be true positives. There were four culture-positive, LCR-negative specimens, all from nonpregnant women. The sensitivity, specificity, and positive and negative predictive values of urine LCR after discrepant results were resolved were 88.6, 99.7, 96.9, and 99.0%, respectively. The sensitivity of culture was 71.4%. From the 148 pregnant women (prevalence by LCR, 6.8%), there were no patients who were cervical culture positive and urine LCR negative to indicate the presence in pregnant women of inhibitors of LCR. Additionally, a subset of 55 of the LCR-negative frozen urine specimens from pregnant women that had been previously processed in LCR buffer were inoculated with 5 cell culture inclusion forming units of C. trachomatis each and retested by LCR; all tested positive, indicating the absence of inhibitors of LCR in urine from these pregnant women. The use of LCR testing of urine specimens from asymptomatic women, whether pregnant or not, offers a sensitive and easy method to detect C. trachomatis infection in women.     

Distribution of Chlamydia trachomatis ompA genovars and the new variant of C. trachomatis in the Göteborg area, Sweden

The aims of this study were to assess the proportion of the new variant of Chlamydia trachomatis (nvCT) and the distribution of ompA genovars among C. trachomatis-positive patients in the Göteborg area, Sweden. Consecutive urine samples positive for C. trachomatis using BD ProbeTec ET (177 patients, 88 men and 89 women) were collected. An nvCT-specific real-time polymerase chain reaction (PCR) assay was used to investigate the nvCT prevalence. To identify the genovars, a 990-bp ompA DNA segment from 105 specimens was sequenced. Seventeen percent (30/177) of all specimens contained nvCT. Nine different genovars were identified. About 50% were of genovar E, followed by F 16%, G 11%, K 8%, and D 5%, representing about 90% of the specimens in Göteborg. The occurrence of nvCT and the dominance of genovar E in Göteborg is similar to those in other areas of Sweden. To cover about 90% of the C. trachomatis infections in Sweden, the serovars D, E, F, G, and K should be included in future vaccines based on the major outer membrane protein.     

Inhibition of PCR in Genital and Urine Specimens Submitted for Chlamydia trachomatis Testing

We determined the frequency of PCR inhibition in genital and urine specimens submitted for Chlamydia trachomatis testing using the internal control DNA provided with the COBAS AMPLICOR C. trachomatis test and assessed methods to remove it. Inhibition occurred in 65 of 906 (7%) cervical swabs, 23 of 51 (45%) urethral swabs, and 2 of 175 (1.1%) urine samples. Overall, inhibition was eliminated in processed specimens after storage at 4°C in 77 of 90 specimens (86%), freezing at −70°C in 59 of 82 specimens (72%), storage at 4°C followed by either 1:100 dilution in 37 of 43 specimens (86%) or 1:10 dilution in 42 of 47 specimens (89%), and phenol-chloroform extraction in 79 of 80 specimens (99%). No positive specimens were missed due to inhibition. We conclude that PCR inhibition is rare with urine specimens and infrequent with endocervical swabs but occurs frequently with urethral swabs. The frequency of PCR inhibition may be significantly reduced by methods which can be easily incorporated into the processing of specimens.     

Performance of the Abbott RealTime CT/NG for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae

A multicenter clinical study was conducted to evaluate the performance characteristics of the Abbott RealTime CT/NG assay, a multiplex real-time PCR assay, for simultaneous detection of Chlamydia trachomatis and Neisseria gonorrhoeae. The specimens were collected from a total of 3,832 male and female subjects at 16 geographically diverse sites. Specimens included male and female urine samples, male urethral swabs, female endocervical swabs, and self-collected and clinician-collected vaginal swabs. Specimens were tested with the automated Abbott RealTime CT/NG assay, Aptima Combo 2 assay (Gen-Probe), ProbeTec ET CT/GC assay (Becton Dickinson), and culture for N. gonorrhoeae. The Aptima Combo 2 assay, the ProbeTec assay, and the N. gonorrhoeae culture were used as the reference assays. For each subject, a patient infected status (PIS) was determined based on the combined results from the reference assays. The overall prevalence in female subjects was 8.9% for C. trachomatis and 3.8% for N. gonorrhoeae. The overall male prevalence was 18.2% for C. trachomatis and 16.7% for N. gonorrhoeae. The overall sensitivity and specificity of the Abbott RealTime CT/NG assay were 92.4% and 99.2% for C. trachomatis and 96.9% and 99.7% for N. gonorrhoeae, respectively. In comparison, the sensitivity and specificity, respectively, for the Aptima Combo 2 assay were 94.5% and 99.0% for C. trachomatis and 96.1% and 99.5% for N. gonorrhoeae, and those for the ProbeTec ET assay were 90.3% and 99.5% for C. trachomatis and 92.0% and 97.3% for N. gonorrhoeae in this study. The Abbott RealTime CT/NG assay offers C. trachomatis and N. gonorrhoeae dual detection with high sensitivity and specificity. The automated assay provides a useful alternative nucleic acid amplification assay for clinical laboratories and clinicians.Chlamydia trachomatis and Neisseria gonorrhoeae are the two most prevalent bacterial sexually transmitted infections (STIs) reported to the Centers for Disease Control and Prevention (CDC) (2). Together these two infections accounted for over 1.5 million cases of STIs in 2008. The CDC estimates that sexually transmitted diseases (STDs) cost the health care system $1.5 billion annually. Since these infections, especially chlamydia, are most often asymptomatic, the CDC recommends yearly screening for chlamydia in all sexually active women ages 16 to 25 years. Since coinfections are common, many diagnostic test platforms assay for both organisms. Although there are several commercial assays available for performing nucleic acid amplification tests (NAATs), which are now recommended by the CDC as the test of choice, new assays and new platforms are needed by both private and public health programs.The Abbott RealTime CT/NG assay is a new real-time PCR assay for the direct, qualitative detection of the plasmid DNA of Chlamydia trachomatis and the genomic DNA of Neisseria gonorrhoeae in female endocervical or vaginal swab specimens, in male urethral swab specimens, and in male and female urine specimens from symptomatic and asymptomatic individuals. There were several sets of objectives of this study: (i) to determine the performance characteristics of the Abbott RealTime CT/NG assay compared to those of other amplified assays using specimens obtained from symptomatic and asymptomatic male and female subjects from clinical sites with high or low prevalence of Chlamydia trachomatis and/or Neisseria gonorrhoeae; (ii) to demonstrate the precision of the Abbott RealTime CT/NG assay using a precision panel consisting of combinations of high and low concentrations of Chlamydia trachomatis and Neisseria gonorrhoeae specimens; (iii) to evaluate the clinical sensitivity, clinical specificity, positive predictive value (PPV), and negative predictive value (NPV) of the Abbott RealTime CT/NG assay in symptomatic and asymptomatic individuals from high- and low-prevalence sites; (iv) to compare the performance of the new Abbott assay with that of the Gen-Probe Aptima Combo 2 assay for female endocervical and vaginal swabs, male urethral swabs, and male and female urine specimens; (v) to compare the performance of the Abbott assay with those of the Becton Dickinson ProbeTec ET Chlamydia trachomatis and Neisseria gonorrhoeae amplified DNA assays (ProbeTec ET) for female endocervical swabs and male and female urine specimens; and (vi) to evaluate the procedure for self-collection of a vaginal swab specimen using the Abbott multi-Collect specimen collection kit.     

Pooling Urine Samples for Ligase Chain Reaction Screening for Genital Chlamydia trachomatis Infection in Asymptomatic Women

The accuracy of pooling urine samples for the detection of genital Chlamydia trachomatis infection by ligase chain reaction (LCR) was examined. A model was also developed to determine the number of samples to be pooled for optimal cost savings at various population prevalences. Estimated costs included technician time, laboratory consumables, and assay costs of testing pooled samples and retesting individual specimens from presumptive positive pools. Estimation of population prevalence based on the pooled LCR results was also applied. After individual urine specimens were processed, 568 specimens were pooled by 4 into 142 pools and another 520 specimens were pooled by 10 into 52 pools. For comparison, all 1,088 urine specimens were tested individually. The sample-to-cut-off ratio was lowered from 1.0 to 0.2 for pooled samples, after a pilot study which tested 148 samples pooled by 4 was conducted. The pooling algorithm was 100% (48 of 48) sensitive when samples were pooled by 4 and 98.4% (61 of 62) sensitive when samples were pooled by 10. Although 2.0% (2 of 99) of the negative pools of 4 and 7.1% (1 of 14) of the negative pools of 10 tested presumptive positive, all samples in these presumptive-positive pools were negative when retested individually, making the pooling algorithm 100% specific. In a population with 8% genital C. trachomatis prevalence, pooling by four would reduce costs by 39%. The model demonstrated that with a lower prevalence of 2%, pooling eight samples would reduce costs by 59%. Pooling urine samples for detection of C. trachomatis by LCR is sensitive, specific, and cost saving compared to testing individual samples.     

Influence of Temperature,Medium, and Storage Duration on Chlamydia trachomatis DNA Detection by PCR

We validated the use of stored samples for Chlamydia trachomatis research. C. trachomatis DNA was detected by real-time PCR in clinical (urine and self-taken vaginal swabs) and spiked samples using six different media, five different time points (up to 2 years), and four different temperature conditions. C. trachomatis was detected in all 423 samples, and no clinically relevant degradation impact was detected.     

Multicenter Evaluation of the Fully Automated COBAS AMPLICOR PCR Test for Detection of Chlamydia trachomatis in Urogenital Specimens

The fully automated COBAS AMPLICOR CT/NG test for the detection of Chlamydia trachomatis was evaluated in a multicenter trial. Test performance was evaluated for 2,014 endocervical swab and 1,278 urine specimens obtained from women and for 373 urethral swab and 254 urine specimens obtained from men. Culture served as the reference test. Culture-negative, COBAS AMPLICOR-positive specimens that tested positive in a confirmatory PCR test for an alternative target sequence within the C. trachomatis major outer membrane protein gene were resolved as true positives. The overall prevalence of chlamydia was 4.3% in cervical swabs and 11.0% in urethral swabs from men. When the results for each specimen type were considered separately, the resolved sensitivities were 96.5% (83 of 86) for endocervical swab specimens, 95.1% (39 of 41) for urine specimens from women, 100.0% (41 of 41) for urethral swab specimens from men, and 94.4% (17 of 18) for urine specimens from men; the resolved specificities were 99.4% (1,912 of 1,924) for endocervical swab specimens, 99.8% (1,204 of 1,207) for urine specimens from women, 98.5% (325 of 330) for urethral swab specimens from men, and 100.0% (236 of 236) for urine specimens from men. For the subset of patients from whom both swab and urine specimens were collected, the combined results for both specimen types were used to identify all infected patients. Using these combined reslts as criteria, the resolved sensitivities for the COBAS AMPLICOR test were 82.6% (38 of 46) for endocervical swab specimens, 84.4% (38 of 45) for urine specimens from women, 84.2% (16 of 19) for urethral swab specimens from men, and 89.5% (17 of 19) for urine specimens from men. In comparison, the sensitivity of culture was only 56.5% (26 of 46) for endocervical specimens and 63.2% (12 of 19) for urethral specimens from men. The internal control provided in the COBAS AMPLICOR test revealed that 2.9% of specimens were inhibitory when they were initially tested. Nevertheless, valid results were obtained for 99.1% of specimens because 68.7% of the inhibitory specimens were not inhibitory when a second aliquot of the original sample was tested. Two additional COBAS AMPLICOR-positive specimens were detected by retesting inhibitory specimens. The COBAS AMPLICOR CT/NG test for the detection of C. trachomatis exhibited equally high sensitivities and specificities with both urogenital swab and urine specimens and, thus, is well-suited for use in screening.     

Investigating the Epidemiology of Repeat Chlamydia trachomatis Detection after Treatment by Using C. trachomatis OmpA Genotyping

Repeat Chlamydia trachomatis detection frequently occurs within months after C. trachomatis infection treatment. The origins of such infection (persistence versus reinfection from untreated or new partners) are varied and difficult to determine. C. trachomatis strains can be differentiated by sequencing the ompA gene encoding the outer membrane protein A (OmpA). We used OmpA genotyping to investigate the epidemiology of repeat C. trachomatis detection after treatment in C. trachomatis-infected subjects seen at a sexually transmitted diseases clinic. Subjects were enrolled, tested for C. trachomatis, treated with azithromycin, and scheduled for a 6-month follow-up for repeat C. trachomatis testing. OmpA genotyping was performed on C. trachomatis-positive urogenital specimens obtained from patients at enrollment and follow-up. The enrollment visit OmpA genotypes for C. trachomatis were determined for 162 subjects (92% female, 94% African American). C. trachomatis was detected at follow-up in 39 subjects (24%). The OmpA genotype distribution at enrollment did not differ in those with versus those without repeat C. trachomatis detection. Of the 35 subjects with C. trachomatis strains genotyped at enrollment and follow-up, 7 (20%) had the same ompA sequence at both visits, while 28 (80%) had discordant sequences. A new sexual partner was reported more often in subjects with discordant C. trachomatis strains than in those with concordant strains (13 [46%] versus 1 [14%]; P = 0.195). Half of the subjects with discordant C. trachomatis strains who reported sexual activity since treatment denied a new sexual partner; 62% of these subjects reported that their partner was treated. Our study demonstrates that most repeat C. trachomatis detections after treatment were new infections with a different C. trachomatis strain rather than reinfection with the same strain. OmpA genotyping can be a useful tool in understanding the origins of repeat C. trachomatis detection after treatment.     

Possible role of Chlamydia trachomatis in the male partner of infertile couples

Chlamydia trachomatis is the most prevalent sexually transmitted bacterial infection, with an estimated 92 million new cases occurring each year worldwide. The aim of the present study was to detect the microorganism from semen samples of asymptomatic male partners of infertile couples using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assays (ELISA). Semen and blood specimens were obtained from 93 infertile and 93 fertile men attending an infertility center by our diagnostic laboratory for the detection of C. trachomatis. The presence of C. trachomatis was examined by PCR assay. Serum IgG and IgA antibodies to C. trachomatis were also monitored using ELISA in all samples. The rates of C. trachomatis infection by PCR were 19.4% and 7.5% in infertile and fertile men, correspondingly, which was significantly different using χ ² test (p?=?0.01). The prevalence of IgG and IgA antibody levels were 4.3% and 2.2% (in infertile) and 3.2% and 1.1% (in fertile men), respectively. The present study showed a remarkable correlation between infections caused by C. trachomatis and infertility in men. Our data revealed that C. trachomatis caused a persistent infection among infertile couples.     

Chlamydia trachomatis causing neonatal conjunctivitis in a tertiary care center

Chlamydia trachomatis is considered a major aetiological agent of conjunctivitis in newborns. The objective of the present study was to determine the aetiology of neonatal conjunctivitis and clinico-epidemiological correlates of chlamydial ophthalmia neonatorum. Fifty-eight newborns with signs and symptoms of conjunctivitis were studied. Conjunctival specimens were subjected to Gram staining, routine bacteriological culture, culture for Neisseria gonorrhoeae and direct fluorescent antibody (DFA) staining for diagnosis of C. trachomatis infection. C. trachomatis was detected in 18 (31%) neonates. Findings suggest that since C. trachomatis is the most common cause of neonatal conjunctivitis, routine screening and treatment of genital C. trachomatis infection in pregnant women and early diagnosis and treatment of neonatal Chlamydial conjunctivitis may be considered for its prevention and control.     

The “3 in 1” Study: Pooling Self-Taken Pharyngeal,Urethral, and Rectal Samples into a Single Sample for Analysis for Detection of Neisseria gonorrhoeae and Chlamydia trachomatis in Men Who Have Sex with Men

Triple-site testing (using pharyngeal, rectal, and urethral/first-void urine samples) for Neisseria gonorrhoeae and Chlamydia trachomatis using nucleic acid amplification tests detects greater numbers of infections among men who have sex with men (MSM). However, triple-site testing represents a cost pressure for services. MSM over 18 years of age were eligible if they requested testing for sexually transmitted infections (STIs), reported recent sexual contact with either C. trachomatis or N. gonorrhoeae, or had symptoms of an STI. Each patient underwent standard-of-care (SOC) triple-site testing, and swabs were taken to form a pooled sample (PS) (pharyngeal, rectal, and urine specimens). The PS was created using two methods during different periods at one clinic, but we analyzed the data in combination because the sensitivity of the two methods did not differ significantly for C. trachomatis (P = 0.774) or N. gonorrhoeae (P = 0.163). The sensitivity of PS testing (92%) was slightly lower than that of SOC testing (96%) for detecting C. trachomatis (P = 0.167). For N. gonorrhoeae, the sensitivity of PS testing (90%) was significantly lower than that of SOC testing (99%) (P < 0.001). When pharynx-only infections were excluded, the sensitivity of PS testing to detect N. gonorrhoeae infections increased to 94%. Our findings show that pooling of self-taken samples could be an effective and cost-saving method, with high negative predictive values. (Interim results of this study were presented at the BASHH 2013 summer meeting.)     

False-negative results of a ligase chain reaction assay to detectChlamydia trachomatis due to inhibitors in urine

The aim of this study was to assess the presence of inhibitors in urine specimens causing false-negative results in a commercialChlamydia trachomatis gap-filling ligase chain reaction (Gap-LCR) assay. On testing of urine samples by the Gap-LCR assay and urethral swab specimens by cell culture, 73 (19%)Chlamydia trachomatis positive subjects were detected among 382 men attending a clinic for sexually transmitted diseases. In 56 subjects, the agent was detected in both the urine and the urethral samples, while 309 subjects were negative in both tests. In seven subjects urine samples were Gap-LCR positive (confirmed by a different Gap-LCR assay), but the corresponding urethral swab samples were cell culture-negative. In another ten subjects the urethral swab samples were cell culture positive, but their urine samples were Gap-LCR negative. Subsequent re-analysis of the urine samples including the addition of externalChlamydia trachomatis DNA indicated full or partial inhibition in nine of the cell culture-positive Gap-LCR negative subjects. When urine preparations were freeze-thawed and diluted prior to testing,Chlamydia trachomatis was detected in six of the ten initially Gap-LCR-negative samples. Gap-LCR inhibitors were present in at least nine (12%) of the 73 urine preparations from theChlamydia trachomatis positive individuals. Identification of samples containing Gap-LCR inhibitors and subsequent processing to reduce the inhibition increased the sensitivity of the test from 86% to 95%.     

Comparative Evaluation of Chlamydiazyme, PACE 2, and AMP-CT Assays for Detection of Chlamydia trachomatis in Endocervical Specimens

We conducted a comparative evaluation of the Chlamydiazyme (Abbott Laboratories), PACE 2 (Gen-Probe), and AMP-CT (Gen-Probe) assays for the detection of Chlamydia trachomatis in endocervical samples. Specimens from 787 females were included in the study. The sensitivities of the PACE 2 and Chlamydiazyme assays in comparison to the results of the AMP-CT assay were 79.3 and 63.4%, respectively. The specificities of the Chlamydiazyme and PACE 2 assays were 100%. All of the positive specimens detected in this study were positive by the AMP-CT assay. On the basis of the final results of the comparison, the prevalence of C. trachomatis in the population was 10.4%. Retesting of specimens whose results were in the intermediate zone by the PACE 2 assay by a probe competition assay identified some additional true-positive specimens. Amplification assay testing of such specimens did not significantly increase the yield. The majority of specimens which tested positive by the AMP-CT assay only were not in the intermediate zone by the PACE 2 assay. We were unable to identify demographic or clinical factors which could predict those individuals who tested positive by amplified tests but not by nonamplified tests. The Gen-Probe PACE 2 assay proved to be superior to the Chlamydiazyme assay for the screening and diagnosis of C. trachomatis infections in female endocervical specimens.