Detection of Chlamydia trachomatis by the Gen-Probe AMPLIFIED Chlamydia Trachomatis Assay (AMP CT) in urine specimens from men and women and endocervical specimens from women

DjinniChip: evaluation of a novel molecular rapid diagnostic device for the detection of Chlamydia trachomatis in trachoma-endemic areas

BACKGROUND

The clinical signs of active trachoma are often present in the absence of ocular Chlamydia trachomatis infection, particularly following mass drug administration. Treatment decisions following impact surveys and in post-control surveillance for communities are currently based on the prevalence of clinical signs, which may result in further unnecessary distribution of mass antibiotic treatment and the increased spread of macrolide resistance alleles in 'off-target' bacterial species. We therefore developed a simple, fast, low cost diagnostic assay (DjinniChip) for diagnosis of ocular C. trachomatis for use by trachoma control programmes.

METHODS

The study was conducted in the UK, Germany and Tanzania. For clinical testing in Tanzania, specimens from a sample of 350 children between the ages of 7 to 15 years, which were part of a longitudinal cohort that began in February 2012 were selected. Two ocular swabs were taken from the right eye. The second swab was collected dry, kept cool in the field and archived at - 80 °C before sample lysis for DjinniChip detection and parallel nucleic acid purification and detection/quantification by qPCR assay.

RESULTS

DjinniChip was able to reliably detect > 10 copies of C. trachomatis per test and correctly identified 7/10 Quality Control for Molecular Diagnostics C. trachomatis panel samples, failing to detect 3 positive samples with genome equivalent amounts ≤ 10 copies. DjinniChip performed well across a range of typical trachoma field conditions and when used by lay personnel using a series of mock samples. In the laboratory in Tanzania, using clinical samples the sensitivity and specificity of DjinniChip for C. trachomatis was 66% (95% CI 51-78) and 94.8 (95% CI 91-97%) with an overall accuracy of 90.1 (95% CI 86.4-93).

CONCLUSIONS

DjinniChip performance is extremely promising, particularly its ability to detect low concentrations of C. trachomatis and its usability in field conditions. The DjinniChip requires further development to reduce inhibition and advance toward a closed system. DjinniChip results did not vary between local laboratory results and typical trachoma field settings, illustrating its potential for use in low-resource areas to prevent unnecessary rounds of MDA and to monitor for C. trachomatis recrudescence.

Accuracy of tests used to detect infection with Chlamydia trachomatis in asymptomatic pregnant women: a systematic review

PURPOSE OF REVIEW

Infection with Chlamydia trachomatis in pregnancy is linked to increased risk of miscarriage, stillbirth, and preterm birth. Currently, PCR or DNA-based tests are the gold standard when detecting the infection; however, they are costly and require access to specialist equipment. The aim of this systematic review was to assess the accuracy of available tests to detect infection in an asymptomatic pregnant population.

RECENT FINDINGS

There was evidence of the superior accuracy of nucleic acid amplification tests to cell culture in nonpregnant asymptomatic women; however, there are multiple commercial nucleic acid amplification tests with varying sensitivities and specificities. There is a gap in current literature on accuracy studies in an asymptomatic pregnant population, particularly within routine antenatal settings.

SUMMARY

There is a need for a point-of-care test for Chlamydia in pregnancy. Future test accuracy studies for this population should aim to use a universally established reference standard. Further research should provide relevant evidence to guide practice.

Human papillomavirus prevalence in paired urine and cervical samples in women invited for cervical cancer screening

With the introduction of Human papillomavirus (HPV) vaccination in young girls in 2007, it is important to monitor HPV infections and epidemiological changes in this target population. The present study has evaluated the detection of human papillomavirus DNA in paired cervical and urine samples to understand if HPV testing in urine could be used as non-invasive method to monitor HPV status in young women. The study enrolled 216 twenty five-year-old women, resident in Florence and invited for the first time to the cervical cancer Screening Program within a project evaluating the impact of HPV vaccination. HPV genotyping was performed on 216 paired urine and cervical samples. The overall concordance between cervix and urine samples, investigated by HPV genotyping (INNO-LiPA HPV Genotyping Extra), was: 85.6% (184/215), 84.6% (182/215), 80% (172/215) when the same HPV, at least the same HR HPV and all HR HPV, respectively, were detected. HPV type specific concordance in paired urine and cervical samples was observed in 85.8% (175/204) of women with normal cytology and in seven out of nine women with abnormal cytology. Urine seems to be a suitable and reliable biological material for HPV DNA detection as evidenced by the high concordance with HPV detected in cervical samples. These results suggest that urine could be a good noninvasive tool to monitor HPV infection in vaccinated women.

Self-administered sample collection for screening of sexually transmitted infection among reservation-based American Indian youth

American Indians suffer a disproportionate burden of sexually transmitted infection, particularly adolescents. Screening access barriers in rural and reservation-based communities necessitate alternatives to clinic-based options. Self-administered screening for three sexually transmitted infections was piloted among 32 American Indian adolescents aged 18 to 19. Participants self-collected in a private location; specimens were processed by trained, American Indian paraprofessionals and analysis was conducted by an outside laboratory. Participants testing positive were treated by a Public Health Nurse from the Indian Health Service. Results suggest high overall acceptability: 69% preferred a self-administered method over clinic-based screening, 75% would encourage their friends to use this method and 100% would use it again. A self-administered screening method has the ability to reach this and other high-risk populations that might not otherwise access screening, with added potential within the Indian Health Services system for uptake and dissemination in rural, reservation communities facing significant screening barriers.

Prevalence of Chlamydia infection among women visiting a gynaecology outpatient department: evaluation of an in-house PCR assay for detection of Chlamydia trachomatis

Background

Screening women for Chlamydia trachomatis infection in developing countries is highly desirable because of asymptomatic infection. The existing diagnostic methods in developing countries are not effective and their sensitivity fall below 45.0% which leads to further spread of infection. There is an urgent need for improved and cost effective diagnostic tests that will reduce the burden of sexually transmitted infections in the developing world.

Methods

Prevalence of C. trachomatis infection among women visiting gynaecology department of Hindu Rao hospital in Delhi, India was determined using Roche Amplicor Multi Well Plate kit (MWP) as well as using in-house PCR assay. We used 593 endocervical swabs for clinical evaluation of the in-house developed assay against Direct Fluorescence Assay (DFA; Group I n = 274) and Roche Amplicor MWP kit (Group II, n = 319 samples) and determined the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of the in-house developed assay.

Results

We detected 23.0% positive cases and there was a higher representation of women aged 18-33 in this group. An in-house PCR assay was developed and evaluated by targeting unique sequence within the gyrA gene of C. trachomatis. Specificity of the reaction was confirmed by using genomic DNA of human and other STI related microorganisms as template. Assay is highly sensitive and can detect as low as 10 fg of C. trachomatis DNA. The resolved sensitivity of in-house PCR was 94.5% compared with 88.0% of DFA assay. The high specificity (98.4%) and sensitivity (97.1%) of the in-house assay against Roche kit and availability of test results within 3 hours allowed for immediate treatment and reduced the risk of potential onward transmission.

Conclusions

The in-house PCR method is cost effective (~ 20.0% of Roche assay) and hence could be a better alternative for routine diagnosis of genital infection by C. trachomatis to facilitate improved screening and treatment management.

Comparison of three methods of DNA extraction in endocervical specimens for Chlamydia trachomatis infection by spectrophotometry, agarose gel, and PCR

Chlamydia trachomatis is the major cause of sexually transmitted disease in the world. The aim of this study was to determine the best method of DNA extraction for detecting C. trachomatis by polymerase chain reaction (PCR) in sexually active women (n = 80) attending Shahid Beheshti Hospital in Isfahan, Iran. Endocervical swabs were collected from 80 women, 22 of whom were asymptomatic and 58 symptomatic. Three different DNA extraction methods were used in this study (phenol-chlorophorm, proteinase K, and boiling). DNA yield was evaluated by spectrophotometry, agarose gel, and PCR. The internal control was assayed by beta-globin primers (PCO4, GH20). The DNA cryptic plasmid was selected as the target for C. trachomatis and samples were examined by PCR using specific KL1 and KL2 primers. It was shown that DNA extraction by boiling was the most sensitive with the highest yield of DNA. Of the 80 samples, 17 (21.25%) showed positivity for C. trachomatis by PCR. The highest rate of C. trachomatis infection was found in the group aged between 35 and 45 years old and those who used withdrawal or an intrauterine device as methods of contraception. It was demonstrated that DNA extraction by boiling was the least expensive and a very rapid method that gave the highest DNA yield. The infection rate in the sexually active women, including symptomatic and asymptomatic, was 21.25%, with a presumably high prevalence compared with other studies done in this field.

Urine‐based testing forChlamydia trachomatisusing polymerase chain reaction, leucocyte esterase and urethral and cervical smears

The performance of Roche polymerase chain reaction (PCR) Amplicor to detect Chlamydia trachomatis in first-voided urine specimens from 422 males and 456 females attending two clinics for sexually transmitted infections was evaluated in comparison with cultures of urethral and cervical specimens. At the same time, the ability of leucocyte esterase (LE) in first-voided urine and the presence of leucocytes in urethral and cervical smears to identify C. trachomatis-infected individuals based on PCR and culture was determined. The prevalence of C. trachomatis infection was 10.9% in men and 7.7% in women. Sensitivity, specificity, positive predictive value and negative predictive value of Amplicor was 93.5%, 99.7%, 97.7% and 99.2% in males and 91.4%, 99.5%, 94.1% and 99.3% in females. All Chlamydia-infected men were identified by means of a combination of urethritis (4 leucocytes in the urethral smear) and/or a positive LE test in urine, although the specificity was only 42.2%. In women, the combination of urethritis and/or cervicitis and/or a positive LE test identified 85.7% of Chlamydia-infected patients with a specificity of 38.2%. It is concluded that a combination of urethral and/or cervical smears and LE testing of urine can be used as a screening test to select patients, especially males, for specific C. trachomatis testing.

Effect of HIV viral load, CD4 cell count and antiretroviral therapy on human papillomavirus prevalence in urine samples of HIV-infected men

HIV-infected patients are at increased risk for persistent human papillomavirus (HPV) infection, the major cause of anogenital cancer. The present study describes the HPV prevalence in urine samples of 243 HIV-infected men and a control group of 231 men. HPV DNA was amplified by the SPF10 polymerase chain reaction primer set. The overall HPV prevalence in HIV-infected men was 27.5% compared with 12.6% in controls (P < 0.01). Infections with high-risk and multiple HPV genotypes were present in both groups. Differences were not statistically significant. A multivariate logistic regression model showed a decreased HPV prevalence associated with use of a nucleoside and a non-nucleoside reverse transcriptase inhibitor combination (P = 0.03). A trend was observed towards a higher HPV prevalence and a lower CD4 cell count. Further prospective studies are needed to determine the role of HPV DNA testing in urine in future screening programmes for anal cancer in men.

Comparison of an in-house PCR assay, direct fluorescence assay and the Roche AMPLICOR Chlamydia trachomatis kit for detection of C. trachomatis

To improve the control of Chlamydia trachomatis infection in India, a rapid, specific and cost-effective method is much needed. We developed an in-house PCR assay by targeting a unique genomic sequence encoding a protein from the C. trachomatis phospholipase D endonuclease superfamily that produces an amplified fragment of 368 bp. The specificity of the primers was confirmed using genomic DNA from other sexually transmitted disease-causing and related micro-organisms and from humans. The assay was highly sensitive and could detect as low as 10 fg C. trachomatis DNA. Clinical evaluation of the in-house-developed PCR was carried out using 450 endocervical specimens that were divided in two groups. In group I (n=274), in-house PCR was evaluated against the direct fluorescence assay. The resolved sensitivity of the in-house PCR method was 97.22 % compared with 88 % for the direct fluorescent antibody assay. In group II (n=176), the in-house PCR was compared with the commercial Roche AMPLICOR MWP CT detection kit. The resolved sensitivity of the in-house PCR assay reported here was 93.1 % and the specificity was 97.46 %, making it a cost-effective alternative for routine diagnosis of genital infection by C. trachomatis. The method should facilitate early detection leading to better prevention and treatment of genital infection in India.

The prevalence of human papillomavirus (HPV) infection in paired urine and cervical smear samples of HIV-infected women

BACKGROUND

HIV-infected women are at increased risk for cervical dysplasia. Cervical dysplasia is caused by persistent infections with certain types of human papillomavirus (HPV). Conventional testing for genital HPV infections requires cervical cytology. A non-invasive screening method by detection of HPV DNA in urine samples is preferable but is not a routine practice.

OBJECTIVES

To investigate the prevalence and concordance of HPV in paired urine and cervical smear samples and cytological results of Pap smears in HIV-infected women.

STUDY DESIGN

Paired urine and cervical smear samples were collected from 27 HIV-infected women.

RESULTS

The HPV prevalence in urine and cervical smear samples was 81.5% and 51.9%, respectively (p = 0.01). The concordance for HPV positivity and negativity between urine and cervical smear samples is 71%. Seven women (25.9%) had an abnormal cervical smear of Pap II or higher. In all urine samples from these cases HPV DNA was detected.

CONCLUSION

In the present study we show that the HPV prevalence in urine and cervical smear samples of HIV-infected women is high and HPV test results are highly concordant. Therefore, urine samples can be used as medium for HPV testing. HPV testing in urine samples is a simple, reliable, non-invasive screening method.

Evaluation of Gen-Probe APTIMA-based Neisseria gonorrhoeae and Chlamydia trachomatis confirmatory testing in a metropolitan setting of high disease prevalence

Prompted by reports challenging the validity of the low-positive Neisseria gonorrhoeae and Chlamydia trachomatis results generated by the APTIMA Combo 2 assay (Gen-Probe, Incorporated) and by a Centers for Disease Control and Prevention recommendation to confirm N. gonorrhoeae- or C. trachomatis-positive screens by using an alternative amplification target, we report on a comparison of this means of confirmation with an in-house algorithm of repeat testing. Primary clinical specimens yielding N. gonorrhoeae- or C. trachomatis-specific luminescent values between 100,000 and 1,000,000 were repeat tested in duplicate. A subset of specimens was forwarded for confirmatory assays (Gen-Probe) individualized for alternative N. gonorrhoeae or C. trachomatis targets. An 18-month audit revealed that 230 of 29,977 C. trachomatis screens (0.8%) and 41 of 29,064 N. gonorrhoeae assays (0.1%) yielded low-positive data. When a subset of 40 low-positive N. gonorrhoeae screens was repeat tested, 20 (50.0%) remained positive; 22 (55.0%) of the screens remained positive following performance of the confirmatory assay. In contrast, repeat testing of 153 low-positive C. trachomatis screens yielded a positive result for fewer specimens (n = 97; 63.4%) than when commercial confirmatory testing was used (n = 124; 81.0%). However, confirmation of the results for additional C. trachomatis screens by use of an alternative target did not translate into significant differences in the calculated overall C. trachomatis-positive screen rates (7.39% by repeat testing versus 7.52% by the confirmatory assay; P = 0.53). Furthermore, use of the confirmatory assay raised the positive predictive value only 1.8% over that of repeat testing. Molecular confirmatory testing did not significantly enhance the reliability of C. trachomatis- or N. gonorrhoeae-specific nucleic acid amplification testing in this metropolitan setting compared to the reliability of repeat testing.

Adult and pediatric emergency department sexually transmitted disease and HIV screening: programmatic overview and outcomes

OBJECTIVES

To measure the prevalence of gonorrhea, chlamydia, and human immunodeficiency virus (HIV) infection among emergency department (ED) patients who accept screening, and to assess treatment outcomes and risks for infection.

METHODS

Research staff offered voluntary testing for gonorrhea and chlamydia (by urine transcription-mediated amplification) and HIV (by enzyme immunoassay/Western blot of oral mucosal transudate) to ED patients. Pediatric (15-21 years) and adult (22-29 years) patients were eligible for gonorrhea and chlamydia testing; patients aged 15-54 years were eligible for HIV testing. The authors surveyed behavioral risks of patients accepting HIV testing.

RESULTS

From November 2003 to May 2004, 497 of 791 eligible pediatric patients (63%) and 1,000 of 2,180 eligible adult patients (46%) accepted screening for gonorrhea, chlamydia, and/or HIV. There were 41 patients infected with gonorrhea, chlamydia, or both among 380 pediatric patients (10.8%) and 11 of 233 adult patients (4.7%); 14 of 52 patients (27%) were treated presumptively by ED clinicians. Through study efforts, 33 of the 38 remaining patients were treated (90% overall treatment). Eight HIV infections were diagnosed: seven of 969 adult patients (0.7%) and one of 459 pediatric patients (0.2%); five HIV-infected patients (63%) received test results, and three (38%) attended an HIV clinic. Gonorrhea or chlamydia infection in pediatric patients was associated with multiple sex partners, same-sex intercourse, and suspicion of sexually transmitted diseases by the ED clinician.

CONCLUSIONS

The high prevalence of gonorrhea and/or chlamydia infection among pediatric ED patients tested supports consideration of expanded screening. Targeted HIV screening with rapid tests merits exploration in the authors' ED, given the low-moderate numbers of patients identified through screening, receiving test results, and linked to care.

A cost-effectiveness evaluation of a jail-based chlamydia screening program for men and its impact on their partners in the community

BACKGROUND

Few cost-effectiveness evaluations of screening men in jails for chlamydia have been published, and none have evaluated the cost-effectiveness of providing partner notification services to the partners of chlamydia-infected inmates.

GOAL

The goal of this study was to evaluate the cost-effectiveness of the chlamydia screening and partner notification programs for men conducted by a Massachusetts jail compared with 3 hypothetical alternatives.

STUDY DESIGN

Using jail cost and testing data, we used decision analyses to compare the cost and effectiveness of universal screening, age-based screening with 2 age cutoffs, and testing of symptomatic inmates at intake using treated cases of chlamydia and gonorrhea as the primary outcome. We also evaluated the cost-effectiveness of adding partner notification to these alternatives.

RESULTS

Universal screening was the most effective and expensive alternative. Age-based screening would have identified slightly fewer cases at half the cost of universal screening. The net cost of partner notification was low. Assuming high sequelae costs in female partners made partner notification a cost-saving intervention.

CONCLUSIONS

Age-based screening could lower costs without substantially sacrificing effectiveness. Notifying partners of infected inmates was a cost-effective adjunct to screening inmates.

Comparison of an rRNA-based and DNA-based nucleic acid amplification test for the detection of Chlamydia trachomatis in trachoma

BACKGROUND/AIM

The World Health Organisation (WHO) hopes to achieve global elimination of trachoma, still the leading cause of preventable blindness worldwide, in part through mass antibiotic treatment. DNA-based nucleic acid amplification tests (NAATs) are currently used to evaluate the success of treatment programmes by measuring the prevalence of C trachomatis infection. Some believe that newer ribosomal RNA (rRNA)-based tests may be much more sensitive since bacterial rRNA is present in amounts up to 10 000 times that of genomic DNA. Others believe that rRNA-based tests are instead less sensitive but more specific, due to the presence of dead or subviable organisms that the test may not detect. This study compares an rRNA-based test to a DNA-based test for the detection of ocular C trachomatis infection in children living in trachoma-endemic villages.

METHODS

An rRNA-based amplification test and DNA-based polymerase chain reaction (PCR) were performed on swab specimens taken from the right upper tarsal conjunctiva of 56 children aged 0-10 years living in two villages in Amhara, Ethiopia.

RESULTS

The rRNA-based test detected ocular C trachomatis infection in 35 (63%) subjects compared with 22 (39%) detected by PCR (McNemar's test, p = 0.0002). The rRNA-based test gave positive results for all subjects that were positive by PCR, and also detected infection in 13 (23%) additional subjects.

CONCLUSION

The rRNA-based test appears to have significantly greater sensitivity than PCR for the detection of ocular chlamydial infection in children in trachoma-endemic villages. Using the rRNA-based test, we may be able to detect infection that was previously missed with PCR. Past studies using DNA-based tests to assess prevalence of infectious trachoma following antibiotic treatment may have underestimated the true prevalence of infection.

Rapid hybridization probe assay and PCR for detection of Chlamydia trachomatis in urinary tract infections: a prospective study

Chlamydia trachomatis is a widespread bacterium that causes trachoma and genital tract infections in humans. The fact that the growth of this pathogen does not normally occur outside living cells poses a challenge in its diagnosis. The present study aimed to compare the efficacies of different molecular and cultural methods in the detection of C. trachomatis in urine samples collected from patients with urinary tract infections. Examined detection methods involved the Gen-Probe C. trachomatis (GP-CT) assay, direct antigen detection by enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) method. The efficacies of these methods were compared to that of the cell culture technique depending on sensitivity, specificity, and accuracy. C. trachomatis was detected in 25 out of 50 (50%) of examined urine samples using the cell culture method. Compared with this standard technique, the GP-CT assay was the most sensitive procedure, being able to detect the pathogen in all positive samples, followed by PCR and ELISA, which showed 60% and 40% sensitivities, respectively. PCR and ELISA displayed the highest level of specificity (100%) compared to the cell culture method with the GP-CT assay showing 40% specificity. The rate of accuracy was comparable between the GP-CT, PCR, and ELISA methods ranging from 70-80% of the accuracy of the cell culture method. The above results suggest that C. trachomatis is a frequent pathogen associated with upper and lower urinary tract infections. Both the GP-CT assay and PCR method can be recommended as reliable detection methods for C. trachomatis, and the GP-CT can be used as a screening tool.

Women find it easy and prefer to collect their own vaginal swabs to diagnose Chlamydia trachomatis or Neisseria gonorrhoeae infections

BACKGROUND

Self-collected specimens can be used to screen asymptomatic women for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC). We surveyed women's opinions on ease and preferences as to sampling after collecting their own vaginal swab and urine and a physician collection of vaginal swab and cervical swab.

METHODS

In 7 North American cities, a questionnaire was used for women after they participated in a clinical trial of nucleic acid amplification testing of various specimens. A total of 1,090 women consenting to gynecologic sampling for CT and GC (82% of those sampled) volunteered to complete the survey. We analyzed the data for ease of self-collection and preferences for a vaginal swab, urine, or cervical swab.

RESULTS

The average age was 26.6 years; 59.6% were black, 25.5% white, 11% Hispanic, 1.9% Asian, and 2% unknown. Thirty-five percent had more than one sex partner in the past 6 months, 84.9% had been previously tested for a sexually transmitted infection (STI), and 49.2% had experienced an STI. A total of 90.4% found it very easy to self-collect a vaginal swab. This was not influenced by age, education, or study site. Seventy-six percent preferred a vaginal swab over a pelvic examination, 60% over a urine collection, and 94% indicated that they would be tested more often if a vaginal swab was available.

CONCLUSION

Self-collected vaginal swabs were easy to collect and patients preferred them over urine and cervical swabs.

High prevalence of human papillomavirus infections in urine samples from human immunodeficiency virus-infected men

Infection with human immunodeficiency virus (HIV) and the resulting immunosuppression are associated with an increased risk for human papillomavirus (HPV) persistence and related malignancies. In the present study we investigated the prevalence of HPV in urine samples from 104 HIV-infected men with low CD4+ cell counts (<100 per mm(3)) and 115 urine samples from HIV-negative men. A high prevalence of HPV DNA (39.4%) was found in the HIV patients. Most of the HPV types were high risk (81.4%), with HPV 52 as the most prevalent type (12.5%), followed by HPV 18 (6.7%), HPV 35 (5.8%), and HPV 70 (4.8%). Multiple HPV genotypes were observed in 17 (41%) of the 41 HPV- and HIV-positive men. In contrast, only 11 (9.6%) HPV DNA-positive cases were observed among the 115 HIV-uninfected men, and 3 (27.3%) contained multiple genotypes. Quantitative analyses indicated that the HPV viral load, as measured in urine samples, is significantly higher in HIV-positive men compared to HIV-negative men. In the present study we show that urine samples are useful for detecting HPV DNA, there is a high prevalence of HPV in HIV-positive men, and the HPV viral load is substantially higher in HIV-positive than in HIV-negative men. More studies are needed to evaluate the risk and natural development of HPV-related malignancies in HIV-positive men.

Nucleic acid amplification tests for gonorrhea and chlamydia: practice and applications

Nucleic acid amplification tests (NAATs), which are highly sensitive and specific, have provided the ability to use alternative sam-ple types for the diagnosis of sexually transmitted infections (STIs). Self-collected genital specimens, such as urine or even vaginal swabs, can now be accurately used to diagnose gonorrhea or chlamydia infections. In many cases, use of these sample types can decrease the necessity for a clinician to perform a pelvic examination on women or to collect a urethral swab from men, thus extending the diagnostic capability for detecting these infections to nonclinic screening venues. As most chlamydia infections and many gonorrhea infections are asymptomatic, the use of NAATs for self-collected samples greatly increases the types and numbers of patients that can be screened outside of clinic settings. Self-sampling also allows clinicians to easily screen patients in the clinic for STIs who are not presenting for pelvic or urogenital examinations. The application of NAATs to self-collected specimens has the potential to augment public health programs designed to control the epidemic of STIs in the community.

Diagnostic Tests for Chlamydial and Gonorrheal Infections

Chlamydia trachomatis and Neisseria gonorrhoeae are the two most prevalent bacterial sexually transmitted infections reported in the United States. The purpose of this article is to review the various tests available for diagnosing C. trachomatis and N. gonorrhoeae. The nucleic acid amplification tests are preferred owing to their high sensitivity and specificity and use on specimens obtained noninvasively. Non-amplified non-culture tests, such as the DNA probe test, remain a choice for settings in which nucleic acid amplification tests are not available or affordable. Culture is recommended for use on conjunctival, oropharyngeal, and rectal specimens and in cases of suspected abuse. In addition, for gonorrhea, culture is recommended when screening in populations with a low prevalence of infection. Point-of-care tests are limited by low sensitivity and should be used for only populations unlikely to return for follow-up.

Urine nucleic acid amplification tests for the diagnosis of sexually transmitted infections in clinical practice

PURPOSE OF REVIEW

With the advent of highly sensitive and specific nucleic acid amplification assays, this report will demonstrate that self-collected genital specimens, such as urine or even vaginal swabs can be accurately used to diagnose sexually transmitted infections.

RECENT FINDINGS

Use of self collected samples can eliminate the necessity of a clinician to perform a pelvic examination for women or collect a urethral swab for men, thus extending the diagnostic capability for sexually transmitted infections to non-clinic screening venues. As many sexually transmitted infections are asymptomatic, this ability to use self-sampling greatly increases the numbers of patients that can be screened, and has the potential to augment public health programs designed to control the epidemic of sexually transmitted infections in the community. Patient collected samples are highly acceptable, highly accurate, and are becoming widely used. Self-sampling also allows clinicians to easily screen patients in the clinic, who are not presenting for pelvic or urogenital examinations, for sexually transmitted infections.

SUMMARY

Highly accurate molecular tests and easily obtained self-collected urogenital samples represent the ideal combination for obtaining the public health goal of decreasing the sexually transmitted infection epidemic among sexually active persons in the United States today.

The effect of urine testing in evaluations of the sensitivity of the Gen-Probe Aptima Combo 2 assay on endocervical swabs for Chlamydia trachomatis and neisseria gonorrhoeae: the infected patient standard reduces sensitivity of single site evaluation

BACKGROUND

The Gen-Probe APTIMA Combo 2 (AC2) assay is a second-generation transcription-mediated amplification assay for the detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG).

GOAL

The goal of this study was to evaluate AC2 performance of endocervical (cx) swabs for the detection of CT and NG using either a specimen or an infected patient standard.

STUDY DESIGN

In a multicenter clinical study, we compared AC2 with Abbott's ligase chain reaction (LCR) and Roche's polymerase chain reaction (PCR; Amplicor or COBAS) for CT, and we compared AC2 with Abbott's LCR and culture for NG. A total of 1569 females were enrolled in the study; we collected cx and first-catch urine (FCU) specimens.

RESULTS

CT prevalence was 13.3% for cx specimens and 13.7% for FCU specimens. NG prevalence was 8.7% and 7.9% for cx and FCU specimens, respectively. When based only on cx specimens, AC2, LCR, and PCR sensitivities for CT were 99.4%, 95.6%, and 95.6%, respectively. However, cx sensitivity for CT was reduced to 92.1%, 86.6%, and 87.1% for each respective assay when based on both cx and FCU specimen results (infected patient standard). NG sensitivities for AC2, LCR, and culture based solely on cx specimen results were 99.2%, 96.1%, and 85.9%, respectively. Based on infected patient standard, the sensitivities of each respective assay were 98.5%, 93.9%, and 84.0%.

CONCLUSIONS

The infected patient standard reduces the sensitivity of the endocervical evaluation because some infected patients are positive only with FCU. The reduction in sensitivity is greater when testing for CT. Specificities improved slightly, because some unique cx positives, initially classified as false-positive were confirmed by a positive FCU result. Sensitivity of AC2 was higher than LCR, PCR, and culture. Specificity was slightly lower, but discrepant analysis (using alternate TMA targets) of apparent AC2 false-positives showed that 75% to 80% were true-positives.

Can the diagnosis of pelvic inflammatory disease be excluded without a bimanual examination?

Now that urine-based tests are available for detection of Chlamydia and gonorrhea, we sought to determine whether history alone could be used to exclude pelvic inflammatory disease (PID) and thus preclude a bimanual examination. The study design was a retrospective chart review. The study population included females aged 15-24 years diagnosed with PID. Outcome measures were documentation of screening symptoms (abdominal pain, dyspareunia, or abnormal vaginal bleeding) in the medical record. Our primary analysis was sensitivity of screening symptoms for identifying patients with PID. At least 1 of the 3 screening symptoms was reported by 93% of the PID group. If absence of all 3 screening symptoms were used as a screening instrument to exclude a bimanual examination, many women with lower genital tract symptoms could be evaluated noninvasively. However, this approach could result in delayed diagnosis of PID in a small number of patients. Before this strategy is adopted, a large prospective study is needed.

Volume effect on sensitivity of nucleic acid amplification tests for detection of Chlamydia trachomatis in urine specimens from females

Nucleic acid amplification tests (NAATs) for the detection of Chlamydia trachomatis are routinely used on first-catch urine (FCU) specimens. We analyzed data from a head-to-head comparison of NAATs on female FCU specimens and found that the volume of urine collected could affect test performance.

Vaginal swabs are appropriate specimens for diagnosis of genital tract infection with Chlamydia trachomatis

Because self-collected vaginal swabs (VS) are potentially very useful for screening asymptomatic women for Chlamydia trachomatis infection, a multicenter study evaluated that specimen with nucleic acid amplification tests (NAATs). The objective was to determine whether VS are equal to Food and Drug Administration (FDA)-cleared specimens (cervical swabs and first-catch urines [FCU]) for diagnosing genital chlamydial infection. All NAATs then commercially available (October 1996 to October 1999) were used (ligase chain reaction [LCx Probe System; Abbott Laboratories, Abbott Park, Ill.]; PCR [Amplicor; Roche Molecular Systems, Branchburg, N.J.]; and transcription-mediated amplification, [Amplified CT Assay; Gen-Probe Inc., San Diego, Calif.]). NAATs were performed on FCU, urethral, cervical, self- and clinician-collected VS. Sensitivity was compared to isolation using cervical and urethral swabs. Agreement of NAAT results between VS and cervical swabs or FCU was calculated. Specimens from 2,517 15- to 25-year-old asymptomatic women attending clinics at nine different centers were evaluated. Results with self- and clinician-collected VS were equivalent and were at least as good as results with FCU and cervical swabs. Across all sites, summary specificities for all specimens were >99%. Among culture-positive women, NAAT sensitivity with VS (93%) was as high as or higher than NAAT sensitivity with cervical swabs (91%) or FCU (80.6%) or culture of cervical swabs (83.5%). VS are appropriate specimens for diagnosing chlamydial genital tract infection by NAATs. That patients can efficiently collect them offers important benefits for screening programs. It would be beneficial for public health programs if the NAAT manufacturers sought FDA clearance for this specimen.

Identification of symptoms that indicate a pelvic examination is necessary to exclude PID in adolescent women

BACKGROUND

Diagnosis of chlamydia, gonorrhea, and vaginitis is now possible in adolescents using urine testing and vaginal swabs obtained by care provider or patient. However, a complete pelvic examination is necessary to diagnose pelvic inflammatory disease (PID). It is thus important to identify patients who might have pelvic inflammatory disease to assure complete gynecologic assessment of genitourinary symptoms.

PURPOSE

To determine whether adolescent patients with pelvic inflammatory disease report predictable symptoms during the medical interview and to determine what proportion of patients diagnosed with PID report at least one predictor symptom.

DESIGN

Observational study.

SETTINGS

Hospital-based adolescent clinic and Job Corps health service.

PATIENTS

A convenience sample (n = 193) of adolescent and young adult women who had a pelvic examination performed to evaluate a wide range of genitourinary symptoms.

MAIN OUTCOME MEASURE

Clinical diagnosis of pelvic inflammatory disease.

ANALYSIS

Sensitivity, specificity, and positive and negative predictive value of predictor symptoms for identifying patients given a diagnosis of pelvic inflammatory disease.

RESULTS

Twenty (10.4%) patients received a clinical diagnosis of PID. Lower abdominal pain was the most common symptom (90.0%) reported by these patients. All of the patients with PID reported either lower abdominal pain or dyspareunia in the medical history compared with 97 (56.1%) of those without PID. The presence of lower abdominal pain and/or dyspareunia in the clinical history yielded a sensitivity of 100%, specificity of 44%, and positive and negative predictive value of 17% and 100%, respectively, for identifying patients given a diagnosis of PID.

CONCLUSION

This study identified two symptoms reported in the medical history (lower abdominal pain and dyspareunia) that were associated with a clinical diagnosis of pelvic inflammatory disease. If lack of these two symptoms was used as a criterion for omitting a pelvic examination, more than one third of the patients in this study could have been evaluated for cervical and vaginal infections with urine and directly obtained vaginal swabs. Although some of these patients might have required a pelvic examination to exclude other causes of abnormal vaginal bleeding, at least 30% of the total sample could have been evaluated without a speculum and bimanual examination. If further studies support these findings, patients with symptoms suggestive of uncomplicated genitourinary infection (e.g., vaginal discharge, vaginal pruritus, or dysuria) who deny lower abdominal pain and dyspareunia can be evaluated with urine and vaginal samples in place of a speculum and bimanual examination.

Performance of the APTIMA Combo 2 assay for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in female urine and endocervical swab specimens

The greater sensitivity of nucleic acid amplification tests (NAATs) for Chlamydia trachomatis and Neisseria gonorrhoeae permits the use of urine and other noninvasive specimens, which can increase the reach and decrease the costs of public health screening programs aimed at controlling these infections. This study evaluated the performance of the APTIMA Combo 2 assay, a multiplex assay based on the transcription-mediated amplification reaction, for the simultaneous detection of both pathogens in endocervical swab and urine specimens from females. Combo 2 assay results were compared with patient infected status, which were available by using other commercial NAATs. Sensitivity and specificity for C. trachomatis were 94.2 and 97.6%, respectively, in swabs and 94.7 and 98.9%, respectively, in first-catch urine (FCU). Sensitivity and specificity for N. gonorrhoeae were 99.2 and 98.7%, respectively, in swabs and 91.3 and 99.3%, respectively, in FCU. The assay reliably detected both infections in coinfected patients. The Combo 2 assay can be recommended for use with endocervical swab and urine specimens from females, especially for screening tests for asymptomatic women in sexually transmitted disease surveillance programs. This Food and Drug Administration-cleared assay can be a useful tool in efforts to reduce the prevalence and incidence of C. trachomatis and N. gonorrhoeae infections in sexually active women and to prevent their costly and serious sequelae.

The natural course of asymptomatic Chlamydia trachomatis infections: 45% clearance and no development of clinical PID after one-year follow-up

The natural course of asymptomatic Chlamydia trachomatis infections in women was studied during one year in a cohort based nested case-control study. Healthy women (n = 744, from four company health services in Amsterdam) with a medical check-up prior to job engagement were included. C. trachomatis-positive women (n = 30, cases) and a randomly selected control group of C. trachomatis-negative women (n = 186, controls) were followed for one year. Urine specimens (at one, six and 12 months) were analysed for the presence of C. trachomatis-DNA and the C. trachomatis-serovars, and questionnaires were filled in. The C. trachomatis prevalence and natural course in relation to demographic and sexual characteristics after one, six and 12 months were studied. The main outcome measures were 1) the prevalence of C. trachomatis using urine specimens; 2) self-reported complaints; 3) clinical symptoms reported to the coordinating physicians. The prevalence of asymptomatic C. trachomatis infections was 4% and there was no correlation with demographic and sexual characteristics. The person/year clearance rate was 44.7% per year. None of the C. trachomatis-positive women developed clinical symptoms or used C. trachomatis specific antibiotic treatment. Women with or without an asymptomatic infection had the same number of self-reported urogenital complaints during follow-up. In persisting infections twice as many C. trachomatis-serovar E infections were detected as compared to clearing infections. Our findings showed that almost half of the asymptomatic C. trachomatis infections in women cleared during one year of follow-up and none developed clinical pelvic inflammatory disease (PID), which is a much lower figure than previously suggested. Therefore these data are important for cost effectiveness calculations in screening programmes for asymptomatic C. trachomatis infections.

Role of Fig2p in agglutination in Saccharomyces cerevisiae

In W303-derived strains, disruption of FIG2 increased agglutinability of alpha cells, but not a cells, and did not alter expression of alpha-agglutinin, binding of 125I-labeled alpha-agglutinin, or mating efficiency. Fig2p overexpression led to alpha-cell-specfic suppression of agglutinability. These results imply that Fig2p is an indirect masker of the active sites in alpha-agglutinin.

Prevalence and incidence of pelvic inflammatory disease in incarcerated adolescents

BACKGROUND

Few recent studies have determined the prevalence and incidence of pelvic inflammatory disease (PID) among adolescents.

GOAL

The goal of this study was to determine these parameters among incarcerated youths.

STUDY DESIGN

Both on admission and during incarceration, consecutive adolescents entering the Harris County, Texas, Juvenile Detention Center were evaluated for symptoms of PID. One of two experienced clinicians examined adolescents with possible PID. For the diagnosis of PID, we used the minimal criteria of the CDC.

RESULTS

In sexually active heterosexual or bisexual adolescents (N = 313), the prevalence of PID at admission was 4.5%; during the first 31 days of incarceration, the incidence density of PID was 3.3 cases/100 person-months, and the cumulative incidence was 2.2%. The prevalence among these youths of chlamydial and/or gonorrheal infection, as determined by urine or cervical testing, was 24.9%.

CONCLUSION

The high prevalence and incidence of PID underscore the need for effective programs to eradicate chlamydial and gonorrheal infections in high-risk youths.

Moving to nucleic acid-based detection of genital Chlamydia trachomatis

Laboratory diagnosis of the bacterium Chlamydia trachomatis has gone through a complete phase of evolution since it was first identified as a significant cause of sexually transmitted infection. As a fragile, obligatory intracellular organism, it was initially only grown in eggs. Subsequently, diagnosis relied on culture in continuous cell lines. To address the limitations of culture, immunological methods were developed and direct antigen detection using enzyme immunoassay and immunofluorescence flourished. With the advent of molecular technologies, nucleic acid-based amplification techniques became the methods of choice, offering improved standard of care for diagnosis and opening up the possibility of screening using noninvasive, patient-acceptable specimens. In this article, the various currently available molecular methods are examined, some of the existing problems discussed and a view on what we think might happen in the next 5 years to the technology and requirement in diagnosis and screening is given.

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.

Evaluation of the NucliSens Basic Kit for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in genital tract specimens using nucleic acid sequence-based amplification of 16S rRNA

We evaluated a new RNA amplification and detection kit, the NucliSens Basic Kit (Organon Teknika), for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in genitourinary specimens. The Basic Kit provides an open platform for RNA amplification and detection and contains isolation reagents for nucleic acid extraction, nucleic acid sequence-based amplification (NASBA) reagents (enzymes and buffers), and a generic ruthenium-labeled probe for electrochemiluminescent (ECL) detection of amplified product. Using freshly purified and titrated stocks of C. trachomatis and N. gonorrhoeae and in vitro-generated RNA transcripts for sensitivity determinations, the Basic Kit detected 1 inclusion-forming unit of C. trachomatis, 1 CFU of N. gonorrhoeae, and 100 RNA molecules of 16S rRNA for both bacteria. The clinical performance of the Basic Kit was evaluated by testing a total of 250 specimens for N. gonorrhoeae by culture and NASBA and a total of 96 specimens for C. trachomatis by PCR and NASBA. The Basic Kit detected 139 of 142 N. gonorrhoeae culture-positive specimens and gave a negative result for 73 of 74 culture-negative specimens, for a sensitivity and specificity of 97.9 and 98.7%, respectively. For C. trachomatis, the Basic Kit detected 24 of 24 PCR-positive specimens and gave a negative result for 71 of 72 PCR-negative specimens, for a sensitivity and specificity of 100 and 98.6%, respectively. The Basic Kit also detected specimens containing both N. gonorrhoeae and C. trachomatis, using a multiplex NASBA assay using primers for both bacteria. The NucliSens Basic Kit offers a versatile platform for the development of sensitive RNA detection assays for sexually transmitted diseases.

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.

Detection of Chlamydia trachomatis in symptomatic and asymptomatic populations with urogenital specimens by AMP CT (Gen-probe incorporated) compared to others commercially available amplification assays

The present study was designed to evaluate the sensitivity and specificity of AMP CT (Gen-Probe Incorporated, San Diego, CA, USA) on urogenital specimens taken from symptomatic patients and on first void urine (FVU) specimens from asymptomatic patients. In symptomatic patients, 618 specimens from 140 men (140 urethral swabs and 140 FVU) and 202 women (202 endocervical swabs and 136 FVU) were tested by using cell culture, AMP CT and Amplicor Chlamydia trachomatis MWP (microwell plate) (Roche Diagnostics, Somerville, NJ, USA) on genital samples, and AMP CT and Amplicor on FVU. A clinical specimen was considered to be truly positive if either the cell culture was positive and/or both AMP CT and Amplicor were positive. In the asymptomatic population, a total of 300 FVU (136 women and 164 men) were tested by four amplification methods, AMP CT, LCx (Abbott, Abbott Park, IL, USA), Amplicor MWP, and Cobas Amplicor. A subject was considered to be infected when two or more amplification methods were positive. In the symptomatic population (prevalence 13%), concordant results were observed in 320/342 cases (93.5%). After analysis of discordant results, the sensitivity of AMP CT, Amplicor, and culture was 100%, 95.5%, 68.8%, respectively, and the specificity was 98.3%, 99.3%, 100% respectively. The number of false negative results by AMP CT in urine, probably due to labile inhibitors, was 3/276 (1%). In the asymptomatic population, the results were concordant in 298/300 (99.3%), seven positive and 291 negative. Two results were considered false positives, one by Cobas Amplicor, one by AMP CT. Compared to other amplification methods, AMP CT is at least as sensitive for the identification of chlamydial infection in symptomatic and asymptomatic men and women on genital or urine specimens.

Touchdown enzyme time release-PCR for detection and identification of Chlamydia trachomatis, C. pneumoniae, and C. psittaci using the 16S and 16S-23S spacer rRNA genes

Three touchdown enzyme time release (TETR)-PCR assays were used to amplify different DNA sequences in the variable regions of the 16S and 16S-23S spacer rRNA genes specific for Chlamydia trachomatis, Chlamydia pneumoniae, and Chlamydia psittaci as improved tests for sensitive diagnosis and rapid species differentiation. The TETR-PCR protocol used 60 cycles of amplification, which provided improved analytical sensitivity (0.004 to 0.063 inclusion-forming unit of Chlamydia species per PCR). The sensitivity of TETR-PCR with primer set CTR 70-CTR 71 was 96.7%, and the specificity was 99.6%, compared to those of the AMPLICOR PCR for the detection of C. trachomatis in vaginal swab samples. TETR-PCR for C. pneumoniae with primer set CPN 90-CPN 91 was 90% sensitive and 93.3% specific compared with a nested PCR with primer set CP1/2-CPC/D for clinical respiratory samples. TETR-PCR for C. psittaci with primer set CPS 100-CPS 101 showed substantial agreement with cell culturing (kappa, 0.78) for animal tissue samples. Primer sets were then combined into a single multiplex TETR-PCR test. The respective 315-, 195-, and 111-bp DNA target products were precisely amplified when DNA from each of the respective Chlamydia species or combinations of them was used. Multiplex chlamydia TETR-PCR correctly identified one strain of each of the 15 serovars of C. trachomatis, 22 isolates of C. pneumoniae, and 20 isolates of C. psittaci. The primer sets were specific for each species. No target products were amplified when DNA from C. pecorum or a variety of other microorganisms was tested for specificity. TETR-PCR with primers selected for specific sequences in the 16S and 16S-23S spacer rRNA genes is a valuable test that could be used either with individual primers or in a multiplex assay for the identification and differentiation of Chlamydia species from culture isolates or for the detection of chlamydiae in clinical samples.

Using a combination of reference tests to assess the accuracy of a new diagnostic test

Often the accuracy of a new diagnostic test must be assessed when a perfect gold standard does not exist. Use of an imperfect reference test biases accuracy estimates of the new test. This paper reviews existing approaches to this problem including discrepant resolution and latent class analysis. Deficiencies with these approaches are identified. A new approach is proposed that combines the results of several imperfect reference tests to define a better reference standard. We call this the composite reference standard (CRS). Using the CRS, accuracy can be assessed using multi-stage sampling designs. Maximum likelihood estimates of accuracy and expressions for the variance of sensitivity and specificity are provided. Data from clinical literature on the detection of Chlamydia trachomatis are used to illustrate and compare the different approaches. Advantages of the CRS relative to other approaches include that the CRS is explicitly defined, does not depend on the results of the new test under investigation, and is easy to interpret.

Ability of the digene hybrid capture II test to identify Chlamydia trachomatis and Neisseria gonorrhoeae in cervical specimens

The Digene Hybrid Capture II (HCII CT/GC) test is a combination test designed to detect Chlamydia trachomatis and Neisseria gonorrhoeae in a single specimen. It is a nucleic acid hybridization test which uses signal amplification to increase sensitivity. We compared its performance to that of culture on cervical specimens from 1,370 women. Direct fluorescent-antibody assay was used to resolve discrepant results for C. trachomatis. Samples were collected with a proprietary cervical brush or with endocervical swabs. The HCII CT/GC test proved to be sensitive and specific in detecting these organisms. Compared to N. gonorrhoeae culture, it had a sensitivity of 93% (87/94) and a specificity of 98.5% (1,244/1,263). Compared to C. trachomatis culture, the sensitivity was 97.7% (129/132) and specificity was 98.2% (1,216/1,238). Testing of some specimens with discrepant results by PCR suggested that the test would actually prove to be even more specific if it were compared to a nucleic acid amplification test (NAAT). The sensitivity of C. trachomatis culture was somewhat less, at 88.6% (117/132). The endocervical brush appeared to be better than Dacron swabs for collecting specimens. The HCII CT/GC test offers an attractive format that allows simultaneous detection of C. trachomatis and N. gonorrhoeae with a single specimen. An initial positive result is followed by repeat tests with probes to identify chlamydiae or gonococci. This test is more sensitive than C. trachomatis culture and is at least as sensitive as culture for gonococci. It deserves further evaluation and comparison with NAATs and may well offer an attractive alternative for diagnosis and screening of these infections.

Determination of Chlamydia trachomatis prevalence in an asymptomatic screening population: performances of the LCx and COBAS Amplicor tests with urine specimens

This study determined the performances of the LCx (Abbott) and COBAS Amplicor (Roche) tests with urine specimens for the detection of Chlamydia trachomatis in an asymptomatic screening population. Randomly selected women and men (age range, 15 to 40 years) registered in 20 general practices in Amsterdam, The Netherlands, were invited to participate in this study. Urine specimens (n = 2, 906; 1,138 specimens from men and 1,717 specimens from women) were tested for C. trachomatis by the COBAS Amplicor (Roche) and LCx (Abbott) tests. Samples which were positive by only one assay were subjected to discrepant analyses by a third assay (in-house plasmid PCR). By the LCx assay C. trachomatis DNA was detected in urine specimens from 46 of 1,717 women and 29 of 1,138 men, while the COBAS Amplicor detected C. trachomatis DNA in 52 and 35 specimens, respectively. When comparing the LCx and COBAS Amplicor tests, 32 test results (20 for women and 12 for men) were discrepant. After discrepant analyses the following sensitivities, specificities, and positive predictive values were found for the LCx and COBAS Amplicor tests: 78.6 versus 98.8%, 99.7 versus 99.9%, and 88.0 versus 95.4%, respectively. No prominent differences were found between men and women with regard to the test performances. After discrepant analyses the overall prevalences of C. trachomatis in women and men were 3.0 and 2.8%, respectively. For both women and men the prevalence in the younger age groups was higher than that in the older age groups. In conclusion, the COBAS Amplicor tests shows better diagnostic characteristics than the LCx assay for the detection of C. trachomatis in urine specimens from an asymptomatic screening population. In this asymptomatic population the overall prevalence of C. trachomatis was 2.9%.

Comparison of the PACE 2 assay, two amplification assays, and Clearview EIA for detection of Chlamydia trachomatis in female endocervical and urine specimens

Screening for sexually transmitted diseases (STDs) in a greater proportion of sexually active patients has become an accepted protocol by most health care providers. The purpose of this study was to compare the current test methods for detection of Chlamydia trachomatis used at the University of South Alabama, the PACE 2 assay (Gen-Probe) and the Clearview EIA (Wampole Laboratories), with two amplification technologies, the AMP CT (Gen-Probe) and LCx (Abbott) assays. In addition, a number of demographic parameters were ascertained by asking questions at the time of examination as well as for health care provider concerns and preferences. One urine and four endocervical swab specimens were collected in random order from 787 female patients attending one of four obstetrics-gynecology clinics. Eighty-seven percent of patients had no STD-related symptoms. Patients were considered positive for C. trachomatis if three or more assays (swab and/or urine) were positive. Abbott and Gen-Probe confirmed discrepant results by alternate amplified assays. A total of 66 true-positive specimens were detected by use of the combination of endocervical swabs and urine specimens. After discrepant analysis, sensitivities for endocervical swab specimens for the EIA and the PACE 2, LCx, and AMP CT assays were 50, 81, 97, and 100%, respectively. Sensitivities for the LCx and AMP CT assays with urine specimens were 98 and 81%, respectively. The prevalence of C. trachomatis was 8.4%, as determined by amplification technology. Overall, the amplification technologies were the most sensitive methods with either swab (AMP CT assay) or urine (LCx assay) specimens. The PACE 2 assay offered the advantage of a simpler and less expensive assay with acceptable sensitivity. The clearview CT EIA, while yielding a rapid in-office result, had unacceptably low sensitivity. The wide variation in performance with amplification assays with urine specimens as reported in both this study and the literature obviates the need to clarify optimal parameters for this specimen type.

Mailed, home-obtained urine specimens: a reliable screening approach for detecting asymptomatic Chlamydia trachomatis infections

The use of mailed, home-obtained urine specimens could facilitate screening programs for the detection of asymptomatic Chlamydia trachomatis infections. Since transport time could have an adverse effect on the sensitivity of C. trachomatis detection by PCR, the influence of DNA degradation on amplification was monitored over the course of 1 week. Therefore, urine specimens were aliquoted on the day of collection or arrival. Two groups of urine specimens were investigated. Group I contains first-void C. trachomatis-positive and -negative urine samples. DNA degradation was monitored in group I samples for 7 days at room temperature (RT) and at 4 degrees C by amplifying different lengths of the human beta-globin gene and the C. trachomatis plasmid target. DNA degradation was observed only for the larger human beta-globin fragments at days 5 to 7 at RT. In contrast, at 4 degrees C all targets could be amplified. Urine specimens were also frozen and thawed before aliquoting to mimic freezing during transport. This resulted in a lower sensitivity for the detection of C. trachomatis after thawing and 3 to 4 days at RT. In addition, mailed, home-obtained C. trachomatis-positive urine specimens (group II) were analyzed for 7 days after arrival by two commercially available C. trachomatis detection systems (PCR and ligase chain reaction [LCR]). The C. trachomatis plasmid target in mailed, home-obtained urine specimens could be amplified by both PCR and LCR after 1 week of storage and/or transport at RT. In conclusion, our findings indicate that mailed, home-obtained urine specimens are suitable for the sensitive detection of asymptomatic C. trachomatis infections by amplification methods, even if the transport time is up to 1 week at RT. These findings support the feasibility and validity of screening programs based on mailed, home-obtained urine specimens. Larger studies should be initiated to confirm our results.

Performance of the Gen-Probe AMPLIFIED Chlamydia Trachomatis Assay in detecting Chlamydia trachomatis in endocervical and urine specimens from women and urethral and urine specimens from men attending sexually transmitted disease and family planning clinics

The Gen-Probe AMPLIFIED Chlamydia Trachomatis Assay (AMP CT) uses transcription-mediated amplification and hybridization protection assay procedures to qualitatively detect Chlamydia trachomatis rRNA in urine, endocervical swab, and urethral specimens. The performance of the AMP CT was compared to that of cell culture for endocervical swab and urine specimens from women and urethral and urine specimens from men. Analysis of specimens with discrepant results was performed by a combination of reculture, direct fluorescent-antibody (DFA) staining of specimen sediment, and amplification which targeted a different chlamydial rRNA. A total of 800 urine samples were tested by the AMP CT (607 from women and 193 from men), and 7. 1% were positive for C. trachomatis, with a sensitivity of 91.2% and a specificity of 99.6% upon discrepant analysis. A total of 926 swab specimens were tested by culture and AMP CT (717 endocervical swab specimens and 209 urethral swab specimens from men), and 7.7% were positive for C. trachomatis, with a sensitivity and specificity of 100% upon discrepant analysis. The AMP CT is a sensitive and specific nucleic acid hybridization assay for the detection of C. trachomatis in endocervical swab specimens from women, urethral swab specimens from men, and urine specimens from men and women.

Urine specimens from pregnant and nonpregnant women inhibitory to amplification of Chlamydia trachomatis nucleic acid by PCR, ligase chain reaction, and transcription-mediated amplification: identification of urinary substances associated with inhibition and removal of inhibitory activity

The presence of endogenous amplification inhibitors in urine may produce false-negative results for the detection of Chlamydia trachomatis nucleic acids by tests such as PCR, ligase chain reaction (LCR), and transcription-mediated amplification (TMA). Consecutive urine specimens from 101 pregnant women and 287 nonpregnant women submitted for urinalysis were processed for C. trachomatis detection. Aliquots were spiked with the equivalent of one C. trachomatis elementary body and were tested by three commercial assays: AMPLICOR CT/NG, Chlamydia LCX, and Chlamydia TMA. The prevalence of inhibitors resulting in complete inhibition of amplification was 4.9% for PCR, 2.6% for LCR, and 7.5% for TMA. In addition, all three assays were partially inhibited by additional urine specimens. Only PCR was more often inhibited by urine from pregnant women than by urine from nonpregnant women (9.9 versus 3.1%; P = 0.011). A complete urinalysis including dipstick and a microscopic examination was performed. Logistic regression analysis revealed that the following substances were associated with amplification inhibition: beta-human chorionic gonadotropin (odds ratio [OR], 3.3) and crystals (OR, 3.3) for PCR, nitrites for LCR (OR, 14.4), and hemoglobin (OR, 3.3), nitrites (OR, 3.3), and crystals (OR, 3.3) for TMA. Aliquots of each inhibitory urine specimen were stored at 4 and -70 degreesC overnight or were extracted with phenol-chloroform and then retested at dilutions of 1:1, 1:4, and 1:10. Most inhibition was removed by storage overnight at 4 or -70 degreesC and a dilution of 1:10 (84% for PCR, 100% for LCR, and 92% for TMA). Five urine specimens (three for PCR and two for TMA) required phenol-chloroform extraction to remove inhibitors. The results indicate that the prevalence of nucleic acid amplification inhibitors in female urine is different for each technology, that this prevalence may be predicted by the presence of urinary factors, and that storage and dilution remove most of the inhibitors.

Genotyping of Chlamydia trachomatis in urine specimens will facilitate large epidemiological studies

The serovars of Chlamydia trachomatis-positive urine specimens (n = 81; as detected by PCR and ligase chain reaction) were successfully analyzed in 94% of cases by omp1 PCR-based RFLP analysis. The use of urine specimens and this simple and sensitive typing method will greatly facilitate epidemiological studies of C. trachomatis serovar distribution in asymptomatic C. trachomatis infections in both females and males.