Comparison of ligase chain reaction and culture for detection of Neisseria gonorrhoeae in genital and extragenital specimens

Impact of Anatomic Site, Specimen Collection Timing, and Patient Symptom Status on Neisseria gonorrhoeae Culture Recovery

BACKGROUND

Neisseria gonorrhoeae culture is required for antimicrobial susceptibility testing, but recovering isolates from clinical specimens is challenging. Although many variables influence culture recovery, studies evaluating the impact of culture specimen collection timing and patient symptom status are limited. This study analyzed urogenital and extragenital culture recovery data from Centers for Disease Control and Prevention's Strengthening the US Response to Resistant Gonorrhea (SURRG) program, a multisite project, which enhances local N. gonorrhoeae culture and antimicrobial susceptibility testing capacity.

METHODS

Eight SURRG jurisdictions collected gonococcal cultures from patients with N. gonorrhoeae-positive nucleic acid amplification test (NAAT) results attending sexually transmitted disease and community clinics. Matched NAAT and culture specimens from the same anatomic site were collected, and culture recovery was assessed. Time between NAAT and culture specimen collection was categorized as same day, 1 to 7 days, 8 to 14 days, or ≥15 days, and patient symptoms were matched to the anatomic site where culture specimens were collected.

RESULTS

From 2018 to 2019, among persons with N. gonorrhoeae-positive NAAT, urethral infections resulted in the highest culture recovery (5927 of 6515 [91.0%]), followed by endocervical (222 of 363 [61.2%]), vaginal (63 of 133 [47.4%]), rectal (1117 of 2805 [39.8%]), and pharyngeal (1019 of 3678 [27.7%]) infections. Culture recovery was highest when specimens were collected on the same day as NAAT specimens and significantly decreased after 7 days. Symptoms were significantly associated with culture recovery at urethral (P = <0.0001) and rectal (P = <0.0001) sites of infection but not endocervical, vaginal, or pharyngeal sites.

CONCLUSIONS

Culture specimen collection timing and patient symptomatic status can impact culture recovery. These findings can guide decisions about culture collection protocols to maximize culture recovery and strengthen detection of antimicrobial-resistant infections.

Self-Collected versus Clinician-Collected Sampling for Chlamydia and Gonorrhea Screening: A Systemic Review and Meta-Analysis

BACKGROUND

The increases in STI rates since the late 1990s in Canada have occurred despite widespread primary care and targeted public health programs and in the setting of universal health care. More innovative interventions are required that would eliminate barriers to STI testing such as internet-based or mail-in home and community service testing for patients that are hard to reach, who refuse to go for clinician-based testing, or who decline an examination. Jurisdictions such as New Zealand and some American states currently use self-collected sampling, but without the required evidence to determine whether self-collected specimens are as accurate as clinician-collected specimens in terms of chlamydia and gonorrhea diagnostic accuracy. The objective of the review is to compare self-collected vaginal, urine, pharyngeal and rectal samples to our reference standard - clinician-collected cervical, urethral, pharyngeal and rectal sampling techniques to identify a positive specimen using nucleic acid amplification test assays.

METHODS

The hierarchical summary receiver operating characteristic and the fixed effect models were used to assess the accuracy of comparable specimens that were collected by patients compared to clinicians. Sensitivity and specificity estimates with 95% confidence intervals (CI) were reported as our main outcome measures.

FINDINGS

We included 21 studies based on over 6100 paired samples. Fourteen included studies examined chlamydia only, 6 compared both gonorrhea and chlamydia separately in the same study, and one examined gonorrhea. The six chlamydia studies comparing self-collection by vaginal swab to a clinician-collected cervical swab had the highest sensitivity (92%, 95% CI 87-95) and specificity (98%, 95% CI 97-99), compared to other specimen-types (urine/urethra or urine/cervix). Six studies compared urine self-samples to urethra clinician-collected samples in males and produced a sensitivity of 88% (95% CI 83-93) and a specificity of 99% (95% CI 0.94-0.99). Taking into account that urine samples may be less sensitive than cervical samples, eight chlamydia studies that compared urine self-collected verses clinician-collected cervical samples had a sensitivity of 87% (95% CI 81-91) and high specificity of 99% (95% CI 0.98-1.00). For gonorrhea testing, self-collected urine samples compared to clinician-collected urethra samples in males produced a sensitivity of 92% (95% CI 83-97) and specificity of 99% (95% CI 0.98-1.00).

CONCLUSION

The sensitivity and specificity of vaginal self-collected swabs compared to swabs collected by clinicians supports the use of vaginal swab as the recommended specimen of choice in home-based screening for chlamydia and gonorrhea. Urine samples for gonorrhea collected by men had comparably high sensitivity and specificity, so could be recommended as they can be left at room temperature for several days, allowing for the possibility of mail-in home-based testing. In populations that may not go for testing at all, do not have the option of clinical testing, or who refuse a clinical examination, self-collected screening would be a good alternative. We recommend that guidelines on how to self-collect gonorrhea and chlamydia urine, vaginal, rectal and pharyngeal specimens be published.

Effect of nucleic acid amplification testing on detection of extragenital gonorrhea and chlamydial infections in men who have sex with men sexually transmitted disease clinic patients

BACKGROUND

In 2010, the Centers for Disease and Control and Prevention recommended using nucleic acid amplification tests (NAATs) for extragenital gonorrhea (GC) and chlamydia (CT) testing because of NAATs' improved sensitivity compared with culture.

METHODS

In 2011, the Public Health-Seattle & King County Sexually Transmitted Disease Clinic introduced NAAT-based testing for extragenital GC and CT infection in men who have sex with men (MSM) using AptimaCombo2. We compared extragenital GC and CT test positivity and infection detection yields in the last year of culture-based testing (2010) to the first year of NAAT testing (2011).

RESULTS

Test positivity of GC increased by 8% for rectal infections (9.0%-9.7%) and 12% for pharyngeal infections (5.8%-6.5%) from 2010 to 2011; CT test positivity increased 61% for rectal infections (7.4%-11.9%). Pharyngeal CT was identified in 2.3% of tested persons in 2011 (not tested in 2010). We calculated the ratio of extragenital cases per 100 urethral infections to adjust for a possible decline in GC/CT incidence in 2011; the GC rectal and pharyngeal ratios increased 77% and 66%, respectively, and the CT rectal ratio increased 127%. The proportion of infected persons with isolated extragenital infections (i.e., extragenital infections without urethral infection) increased from 43% in 2010 to 57% in 2011.

CONCLUSIONS

Extragenital testing with NAAT substantially increases the number of infected MSM identified with GC or CT infection and should continue to be promoted.

Investigating the potential public health benefit of jail-based screening and treatment programs for chlamydia

Observational studies have found mixed results on the impact of jail-based chlamydia screen-and-treat programs on community prevalence. In the absence of controlled trials or prospectively designed studies, dynamic mathematical models that incorporate movements in and out of jail and sexual contacts (including disease transmission) can provide useful information. We explored the impact of jail-based chlamydia screening on a hypothetical community's prevalence with a deterministic compartmental model focusing on heterosexual transmission. Parameter values were obtained from the published literature. Two analyses were conducted. One used national values (large community); the other used values reported among African Americans--the population with the highest incarceration rates and chlamydia burden (small community). A comprehensive sensitivity analysis was carried out. For the large-community analysis, chlamydia prevalence decreased by 13% (from 2.3% to 2.0%), and based on the ranges of parameter values (including screening coverage of 10%-100% and a postscreening treatment rate of 50%-100%) used in the sensitivity analysis, this decrease ranged from 0.1% to 58%. For the small-community analysis, chlamydia prevalence decreased by 54% (from 4.6% to 2.1%). Jail-based chlamydia screen-and-treat programs have the potential to reduce chlamydia prevalence in communities with high incarceration rates. However, the magnitude of this potential decrease is subject to considerable uncertainty.

The use and performance of oral-throat rinses to detect pharyngeal Neisseria gonorrhoeae and Chlamydia trachomatis infections

Gonococcal and chlamydial infections in the pharynx can occur as a consequence of oral sex. Currently, diagnosis of these infections typically requires a swab specimen to be collected from the posterior pharynx. However, we assessed the diagnostic adequacy of using commercial mouthwash or water as an oral-throat rinse and subsequent testing with a nucleic acid amplification test (Gen-Probe APTIMA Combo 2 assay; Gen-Probe, San Diego, CA). Mouthwash and water samples, spiked with varying amounts of gonorrhea and chlamydia, remained positive for both organisms for up to 2 weeks after storage at room temperature and 37 degrees C. A clinical trial compared the test performance of oral-throat rinses to pharyngeal swabs among 561 (250 mouthwash, 311 water) gay and other men who have sex with men. Participants were also surveyed to assess the acceptability, preference, and feasibility of oral-throat rinses in a clinical setting. The prevalence of pharyngeal gonorrhea and chlamydia were 9.5% (53/556) and 1.4% (8/561), respectively. Compared with the pharyngeal swab, mouthwash oral-throat rinses had a sensitivity and specificity for the detection of gonorrhea of 72% and 99.1%, respectively, whereas water had 82% and 99.7%, respectively. Chlamydia prevalence was too low for reliable assessments of test performance. Study participants found oral-throat rinses acceptable, preferable, and feasible when compared with pharyngeal swabs. Further study is needed to investigate discordant results and improve the sensitivity of oral-throat rinses.

Pyrosequencing of the DNA gyrase gene in Neisseria species: effective indicator of ciprofloxacin resistance in Neisseria gonorrhoeae

The quinolone resistance determining region (QRDR) of the gyrA gene in ciprofloxacin-susceptible strains (n=53) and strains of Neisseria spp. with reduced susceptibility (n=70) was determined by the pyrosequencing method. Results showed that the QRDR of the gyrA gene is an effective molecular indicator of resistance to ciprofloxacin in Neisseria gonorrhoeae, and presumably in Neisseria meningitidis, but not in all other Neisseria spp. This sequence was not unique for N. gonorrhoeae and seems unsuitable for species verification of N. gonorrhoeae. However, whether it is also possible to use this region for verification depends on the specificity of the primary screening method used.

Prevalence and Incidence of Pharyngeal Gonorrhea in a Longitudinal Sample of Men Who Have Sex with Men: The EXPLORE Study

BACKGROUND

The prevalence of gonorrhea of the pharynx among select samples of men who have sex with men (MSM) ranges from 9% to 15%. To our knowledge, there have been no longitudinal studies in a prospective MSM cohort to estimate pharyngeal gonorrhea incidence or predictors of infection. We examined the prevalence, incidence, and sociodemographic and behavioral predictors of pharyngeal gonorrhea in a cohort of sexually active, human immunodeficiency virus-negative MSM.

METHODS

We conducted a prospective study of pharyngeal gonorrhea among MSM who were enrolled in a behavioral intervention study to prevent human immunodeficiency virus infection (Project EXPLORE). Participants were enrolled in this ancillary study from March 2001 through July 2003. At baseline and every 6 months thereafter until 31 July 2003, participants were tested for pharyngeal gonorrhea and were administered a questionnaire regarding their oral sex practices. Rectal and urethral gonorrhea testing were also performed.

RESULTS

Prevalence of pharyngeal gonorrhea was 5.5% (136 cases diagnosed from 2475 tests). The incidence rate was 11.2 cases per 100 person-years. Pharyngeal gonorrhea was positively associated with younger age and the number of insertive oral sex partners in the past 3 months. Ejaculation did not increase the risk of pharyngeal gonorrhea. Gonorrhea of the pharynx was asymptomatic in 92% of cases.

CONCLUSIONS

The pharynx is a common, asymptomatic reservoir for gonorrhea in sexually active MSM.

Nucleic acid amplification testing for Neisseria gonorrhoeae: an ongoing challenge

Nucleic acid amplification tests (NAATs) for the detection of Neisseria gonorrhoeae became available in the early 1990s. Although offering several advantages over traditional detection methods, N. gonorrhoeae NAATs do have some limitations. These include cost, risk of carryover contamination, inhibition, and inability to provide antibiotic resistance data. In addition, there are sequence-related limitations that are unique to N. gonorrhoeae NAATs. In particular, false-positive results are a major consideration. These primarily stem from the frequent horizontal genetic exchange occurring within the Neisseria genus, leading to commensal Neisseria species acquiring N. gonorrhoeae genes. Furthermore, some N. gonorrhoeae subtypes may lack specific sequences targeted by a particular NAAT. Therefore, NAAT false-negative results because of sequence variation may occur in some gonococcal populations. Overall, the N. gonorrhoeae species continues to present a considerable challenge for molecular diagnostics. The need to evaluate N. gonorrhoeae NAATs before their use in any new patient population and to educate physicians on the limitations of these tests is emphasized in this review.

Changes in the Etiology of Sexually Transmitted Diseases in Botswana between 1993 and 2002: Implications for the Clinical Management of Genital Ulcer Disease

BACKGROUND

In recent years, increasing evidence has accumulated that suggests the majority of cases of genital ulcer disease in sub-Saharan Africa are due to viral and not bacterial infections. Although many cross-sectional studies support such a trend, few serial cross-sectional data are available to show the evolution of genital ulcer disease over time.

METHODS

We surveyed the prevalence of sexually transmitted diseases (STDs) among patients with STD symptoms and women recruited from family planning clinics in 3 cities in Botswana in 2002 and compared our findings with those from a survey of a similar population conducted in 1993.

RESULTS

The observed proportion of cases of genital ulcer disease due to chancroid decreased from 25% in 1993 to 1% in 2002, whereas the proportion of ulcers due to herpes simplex virus increased from 23% in 1993 to 58% in 2002. Although the proportion of ulcers due to syphilis was similar for both surveys, the rate of positive serologic test results for syphilis among patients with genital ulcer disease decreased from 52% in 1993 to 5% in 2002. During this period, decreases in the prevalence of gonorrhea, syphilis-reactive serologic findings, chlamydial infection, and trichomoniasis were also detected among patients with STDs and women from family planning clinics. These changes remained significant after estimates were adjusted for the sensitivity and specificity of diagnostic tests.

CONCLUSIONS

Our findings suggest a decrease in the prevalence of bacterial STDs and trichomoniasis, a reduction in the proportion of ulcers due to bacterial causes, and an increase in the proportion of ulcers due to herpes simplex virus during the period 1993-2002. These changes should be taken into consideration when defining new guidelines for the syndromic management of genital ulcer disease.

A Cost-Effectiveness Analysis of Interventions to Increase Repeat Testing in Patients Treated for Gonorrhea or Chlamydia at Public Sexually Transmitted Disease Clinics

BACKGROUND

Persons who have been infected with chlamydia or gonorrhea (CT/GC) are at elevated risk for reinfection. The cost-effectiveness of interventions designed to encourage public sexually transmitted disease (STD) clinic patients to return for rescreening has not been well-evaluated.

GOAL

The goal of this study was to conduct a program- and societal-perspective cost-effectiveness analysis of five interventions designed to encourage public STD clinic patients infected with CT/GC to return for rescreening 3 months after initial treatment.

STUDY

Researchers at two STD clinics collected cost data for the five interventions. These were combined with study data on return rates and CT/GC positivity rates among returning patients to compare the cost-effectiveness of the interventions.

RESULTS

The cost per patient counseled with a brief recommendation to return, followed by a telephone reminder after 3 months, was higher than two interventions: a brief recommendation to return with no reminder and a $20 incentive, received on return. However, the brief recommendation with a telephone reminder yielded the highest return rate (33%) and was the least costly in terms of cost per infection treated ($622 program, $813 societal). In-depth motivational counseling that helped clients identify risk factors and provided reasons for returning was more costly than a phone reminder alone and was not more effective.

CONCLUSIONS

Phone reminders are more cost-effective than motivational counseling and improve return rates over a brief recommendation given at the time of initial treatment.

The Cost Effectiveness of Gonorrhea Screening in Urban Emergency Departments

BACKGROUND

The prevalence of gonorrhea (GC) among adolescent and young women attending some urban emergency departments (EDs) ranges from 1% to 7%, but historically screening has not been logistically practical.

GOAL

The primary goal of the study was to assess the cost effectiveness of GC screening in women ages 15 to 29, seeking care in urban EDs, using noninvasive or rapid point-of-care tests.

STUDY

We developed a state-transition Markov model to compare the net lifetime health consequences, costs, and cost effectiveness of routine ED care (no screening for women without genitourinary symptoms) to GC screening using 1 of 5 detection methods: Gram-stained smears of endocervical swab specimens, urine-based nucleic acid amplification tests (NAATs), NAATs performed on endocervical swabs, rapid immunochromotographic strip test (RIS) performed on clinician-collected vaginal swabs, and RIS on patient-collected vaginal swabs.

RESULTS

Screening women between 15 and 29 years of age using urine-based NAATs prevented 1247 cases of pelvic inflammatory disease (PID) and saved 177 US dollars per patient compared with no screening. Compared with urine-based NAAT, screening with RIS using clinician-obtained vaginal swabs prevented an additional 220 cases of PID and had an incremental cost effectiveness ratio of 6490 US dollars per quality-adjusted life year (QALY). Results were sensitive to assumptions about loss to follow-up, gonorrhea prevalence, and test costs.

CONCLUSION

Screening females aged 15 to 29 for gonorrhea in some urban EDs will prevent substantial reproductive morbidity. Screening with rapid, point-of-care tests is cost effective compared with other well-accepted preventive interventions.

Prevalence of rectal, urethral, and pharyngeal chlamydia and gonorrhea detected in 2 clinical settings among men who have sex with men: San Francisco, California, 2003

BACKGROUND

The Centers for Disease Control and Prevention developed screening and diagnostic testing guidelines for chlamydia and gonorrhea at urethral, rectal, and pharyngeal sites for men who have sex with men (MSM). However, in most clinical settings, rectal chlamydial testing is not performed for MSM, and primarily sexually transmitted disease (STD) clinics alone perform routine rectal and pharyngeal gonorrhea screening for asymptomatic men.

METHODS

We evaluated the prevalence of rectal, urethral, and pharyngeal chlamydial and gonococcal infections among MSM seen at the municipal STD clinic and the gay men's community health center. We also determined the proportion of asymptomatic rectal infections, described the patterns of single and multiple anatomic sites of infection, and evaluated the proportion of chlamydial infections that would be missed and not treated if MSM were not routinely tested for chlamydia. We tested specimens using previously validated nucleic acid amplification tests (NAATs).

RESULTS

The prevalence of infection varied by anatomic site (chlamydia: rectal, 7.9%; urethral, 5.2%; and pharyngeal, 1.4%; for gonorrhea, rectal, 6.9%; urethral, 6.0%; and pharyngeal, 9.2%). Approximately 85% of rectal infections were asymptomatic supporting the need for routine screening. Because 53% of chlamydial infections and 64% of gonococcal infections were at nonurethral sites, these infections would be missed and not treated if only urethral screening was performed. In addition, >70% of chlamydial infections would be missed and not treated if MSM were tested only for gonorrhea.

CONCLUSIONS

Because these infections enhance both HIV transmission and susceptibility, clinical settings serving MSM should evaluate the prevalence of chlamydial and gonococcal infections by anatomic site using validated NAATs.

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

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

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

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

The laboratory diagnosis of gonorrhoea and syphilis infection

Following a decline in prevalence during the 1980s and early 1990s, gonorrhoea and syphilis infections are once again posing a threat to public health. In addition, the antibiotic sensitivity pattern for gonorrhoea appears to have changed with an increased prevalence of resistance. Both syphilis and gonorrhoea appear to disproportionately affect MSM and black ethnic minorities, and are concentrated in urban areas. Their diagnosis requires microbiological tests to be performed appropriately, and a rapid diagnosis can often be provided in GUM clinics using near-patient microscopy. Early diagnosis and effective, rapid treatment is crucial in limiting the morbidity for the affected individual and the public health risks resulting from the spread of infection.

Evaluation of ligase chain reaction for the non-cultural detection of rectal and pharyngeal gonorrhoea in men who have sex with men

OBJECTIVES

To compare a nucleic acid amplification test (ligase chain reaction) with culture for detecting rectal and pharyngeal gonorrhoea in men who have sex with men (MSM).

METHODS

Duplicate rectal and throat swabs from MSM attending a genitourinary medicine clinic were collected for culture on modified New York City medium and detection of gonococcal nucleic acid by the Abbott ligase chain reaction (LCR) utilising probes based on opa 1 gene sequences. LCR positive culture negative specimens were tested by a second LCR utilising probes based on pilin gene sequences. Patients with rectal and/or pharyngeal cultures yielding Gram negative diplococci confirmed as Neisseria gonorrhoeae by biochemical and immunological methods were diagnosed with rectal and/or pharyngeal gonorrhoea. The criteria for diagnosing rectal and pharyngeal infection by LCR included a positive opa LCR with a positive culture from the same site or, in the case of a negative culture, a positive opa LCR and a positive pilin LCR.

RESULTS

Duplicate rectal samples were obtained from 227 MSM. The results of LCR and culture were concordant in 219 samples (96.5%). The prevalence of rectal gonorrhoea by LCR and culture was 7.0% (16/227) and 4.0% (9/227), respectively. Duplicate throat samples were obtained from 251 MSM. The results of LCR and culture were concordant in 230 (91.6%) cases. The prevalence of pharyngeal gonorrhoea by LCR and culture was 12.7% (32/251) and 6.0% (15/251), respectively. The specificity of LCR was 99.5% (210/211) for rectal and 98.2% (215/219) for pharyngeal specimens.

CONCLUSIONS

The high prevalence and asymptomatic nature of pharyngeal and rectal gonococcal infection suggests that routine screening for infection at these sites by a nucleic acid amplification test method such as LCR should be considered as part of the overall strategy to control gonorrhoea in MSM.

Comparison of STD prevalences in the Mwanza, Rakai, and Masaka trial populations: the role of selection bias and diagnostic errors

OBJECTIVES

To assess bias in estimates of STD prevalence in population based surveys resulting from diagnostic error and selection bias. To evaluate the effects of such biases on STD prevalence estimates from three community randomised trials of STD treatment for HIV prevention in Masaka and Rakai, Uganda and Mwanza, Tanzania.

METHODS

Age and sex stratified prevalences of gonorrhoea, chlamydia, syphilis, HSV-2 infection, and trichomoniasis observed at baseline in the three trials were adjusted for sensitivity and specificity of diagnostic tests and for sample selection criteria.

RESULTS

STD prevalences were underestimated in all three populations because of diagnostic errors and selection bias. After adjustment, gonorrhoea prevalence was higher in men and women in Mwanza (2.8% and 2.3%) compared to Rakai (1.1% and 1.9%) and Masaka (0.9% and 1.8%). Chlamydia prevalence was higher in women in Mwanza (13.0%) compared to Rakai (3.2%) and Masaka (1.6%) but similar in men (2.3% in Mwanza, 2.7% in Rakai, and 2.2% in Masaka). Prevalence of trichomoniasis was higher in women in Mwanza compared to women in Rakai (41.9% versus 30.8%). Herpes simplex virus type 2 (HSV-2) seroprevalence and prevalence of serological syphilis (TPHA+/RPR+) were similar in the three populations but the prevalence of high titre syphilis (TPHA+/RPR >/=1:8) in men and women was higher in Mwanza (5.6% and 6.3%) than in Rakai (2.3% and 1.4%) and Masaka (1.2% and 0.7%).

CONCLUSIONS

Limited sensitivity of diagnostic and screening tests led to underestimation of STD prevalence in all three trials but especially in Mwanza. Adjusted prevalences of curable STD were higher in Mwanza than in Rakai and Masaka.

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

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

A cost-effectiveness evaluation of testing and treatment of Chlamydia trachomatis infection among asymptomatic women infected with Neisseria gonorrhoeae

BACKGROUND

Because patients infected with Neisseria gonorrhoeae are frequently coinfected with Chlamydia trachomatis, routine dual treatment of patients with N gonorrhoeae infection is frequently practiced and has long been recommended.

GOAL

The goal of this study was to examine the cost-effectiveness of routine dual treatment of women with infection, with or without separate testing for C trachomatis, compared with an alternative of testing for both infections and restricting treatment for C trachomatis to women testing positive for C trachomatis.

STUDY DESIGN

A decision analysis compared the cost-effectiveness of these options using cases of pelvic inflammatory disease prevented as the outcome. Parameter values were taken from the literature.

RESULTS

Routine dual treatment is not an effective or cost-effective replacement for testing for C trachomatis, but it can increase the number of cases of C trachomatis treated when combined with testing. Dual treatment results in more overtreatment of infection C trachomatis than treatment based on test results.

CONCLUSIONS

Testing for both infections is more cost-effective than routine presumptive treatment for C trachomatis. Providing both presumptive treatment and testing for C trachomatis can also be cost-effective in some settings.

Coexistence of urethritis with genital ulcer disease in South Africa: influence on provision of syndromic management

OBJECTIVE

To assess whether syndromic management of genital ulcer disease was sound, if based on the premise that men with genital ulcers rarely have a concomitant urethral infection.

METHODS

Specimens were taken in 1998 from 186 mine workers in Carletonville, South Africa, who were seen consecutively with genital ulcers. The specimens comprised a swab from the ulcer, a urethral swab for a Gram stained smear, and 10-15 ml of a first catch urine sample. The latter was tested by ligase chain reaction assays for Neisseria gonorrhoeae and Chlamydia trachomatis specific DNA sequences and by a polymerase chain reaction (PCR) assay for Mycoplasma genitalium. Ulcer inducing micro-organisms were detected either by a multiplex PCR assay, or in the case of lymphogranuloma venereum (LGV) serologically, and human immunodeficiency virus (HIV) infection was detected by an enzyme linked immunosorbent assay (ELISA) test.

RESULTS

Most (54%) of the ulcers were chancroidal, 18% were herpetic (HSV type 2), 6.5% primary syphilitic, and 3.2% due to LGV. More than one micro-organism was detected in 9.1% of the ulcers and less than 10% were undiagnosed. Microscopic examination of the urethral smears showed that 99 (53%) of the men had urethritis, of whom 45 (45%) were infected with N gonorrhoeae. Of the 54 men (55%) who had non-gonococcal urethritis (NGU), 11 (19.6%) harboured C trachomatis or M genitalium. Almost two thirds (64.5%) of the men had HIV infection, but this did not seem to have influenced the aetiology of the ulcers. Nor was a particular ulcer associated with one type of urethritis more than the other. Neither C trachomatis nor M genitalium was associated significantly with non-gonococcal urethritis (NGU) in either HIV positive or HIV negative men.

CONCLUSION

The combination of antibiotics used for the management of genital ulcer disease in men in this South African mining population needs to be widened to encompass frequently occurring concomitant gonococcal urethritis and NGU infections. This means treatment with long acting penicillin, combined with ciprofloxacin and azithromycin or erythromycin. A similar situation may exist in other geographical locations with a need to provide appropriate antimicrobial combinations depending on the patterns of infection detected.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cost-effectiveness of five strategies for gonorrhea and chlamydia control among female and male emergency department patients

BACKGROUND

Previous studies have shown screening for gonorrhea and chlamydia to be cost-effective for limiting the sequelae of infection and the associated costs of management.

GOAL

To evaluate the cost-effectiveness of enhanced screening for gonorrhea and chlamydia in an emergency department (ED) setting.

STUDY DESIGN

Five strategies were compared with use of decision analysis for theoretical cohorts of 10,000 female and 10,000 male ED patients aged 18 years to 31 years: standard ED practice, three enhanced screening strategies, and mass treatment. Main outcome measures were untreated gonorrhea or chlamydia cases and their sequelae, transmission to a partner, congenital outcomes, and cost to prevent a case. This analysis, from the perspective of the healthcare sector, included medical case costs expressed in US dollars (1999), discounted at an annual rate of 3%.

RESULTS

Mass treatment was the most cost-effective strategy among women and men. Of the screening strategies for women, universal screening combined with standard practice was the most cost-effective; it was used for treating 499 more cases of gonorrhea and chlamydia than was standard practice, saving $95.70 per case treated. Standard ED practice remained the most cost-effective strategy for men under a variety of circumstances.

CONCLUSION

The authors recommend urine ligase chain reaction screening for gonorrhea and chlamydia in women aged 18 years to 31 years in the ED, in conjunction with standard ED practice, to decrease the occurrence of the sequelae and costs associated with infection.

Increased sensitivity of DNA amplification testing for the detection of pharyngeal gonorrhea in men who have sex with men

We compared ligase chain reaction (LCR) assay with standard culture for the detection of pharyngeal Neisseria gonorrhoeae infection in men who have sex with men (MSM) presenting at a sexually transmitted diseases clinic in San Francisco. Pharyngeal specimens were obtained from 200 MSM who reported performing fellatio during the previous 2 weeks. Confirmatory testing of discrepant specimens was conducted using N. gonorrhoeae pilin proteins. Prevalence of pharyngeal N. gonorrhoeae was 6% by culture or 11% by LCR. The sensitivity and specificity of LCR were 94.7% and 97.8%, respectively, compared with values of 47.4% and 100% for culture. Prevalence of pharyngeal N. gonorrhoeae infection, as determined by DNA amplification testing, was higher than that suggested by traditional culture. Results support the use of DNA amplification testing in the oropharynx. The high prevalence of pharyngeal N. gonorrhoeae infection among MSM suggests that routine screening should be considered in efforts to reduce the burden of gonorrhea in this population.

Correlation between urine and cervical specimens for the detection of cervical Chlamydia trachomatis and Neisseria gonorrhoeae using ligase chain reaction in a cohort of HIV infected and uninfected adolescents

PURPOSE

(a) To examine the concordance between ligase chain reaction (LCR) results from urine and cervical samples for Chlamydia trachomatis and Neisseria gonorrhoeae in HIV infected and uninfected adolescent women, and (b) to examine factors that may influence the concordance of LCR results in this population.

METHODS

Baseline specimens from 269 of 334 female subjects enrolled in a longitudinal study of HIV infection in adolescents were analyzed for C. trachomatis and N. gonorrhoeae using ligase chain reaction (LCR) assays in a central laboratory. Concordance was measured using kappa coefficient with permutation analyses to calculate the difference between HIV status groups. Discordant LCR results were examined for the co-infection with the other microorganism, bacterial vaginosis, or Trichomonas vaginalis.

RESULTS

The prevalence of C. trachomatis detected by LCR in the HIV infected and uninfected groups was 19.3% and 12.2%, respectively (p = .16); the prevalence of N. gonorrhoeae was 7.0% and 2.4%, respectively (p = .16). Urine LCR assay sensitivity to detect cervical C. trachomatis infection was 86% (95% CI: 68%-96%) in the HIV infected group and 100% (95% CI: 69%-100%) in the HIV uninfected group. Urine LCR assay sensitivity to detect cervical N. gonorrhoeae infection was 92% (95% CI: 62%-100%) in the HIV infected group. There were only 2 N. gonorrhoeae infections in the HIV uninfected group, and both were urine LCR positive. Differences in sensitivity between HIV infected and HIV uninfected subjects were not statistically significant. Coinfection with N. gonorrhoeae, bacterial vaginosis or Trichomonas vaginalis was not associated with the concordance of urine and cervical LCR results.

CONCLUSION

The relatively high sensitivity of urine LCR testing overall suggests that urine screening may be reasonable for sexually active adolescent females with or without HIV infection in situations in which urine screening may be more acceptable than pelvic examinations.

Enhancing the specificity of the COBAS AMPLICOR CT/NG test for Neisseria gonorrhoeae by retesting specimens with equivocal results

The COBAS AMPLICOR CT/NG test for Neisseria gonorrhoeae cross-reacts with certain strains of nonpathogenic Neisseria species. In some strains, the target sequence is identical to that of N. gonorrhoeae, whereas other strains have a small number of mismatches within the regions recognized by the primers or probe used in the COBAS AMPLICOR NG test. These cross-reactive strains are occasionally present in urogenital specimens, causing false-positive results in the COBAS AMPLICOR NG test. Analysis of the data generated in a large multicenter clinical trial showed that 2.9% of the specimens gave signals between A(660)s of 0.2 and 3.5 but that one-half of these equivocal specimens did not contain N. gonorrhoeae. Most of these equivocal specimens were correctly classified as true positive or true negative by retesting in duplicate and defining a PCR-positive result as two of three results with an A(660) of > or =2.0. If specimens had been classified as positive or negative based on a single test result using a cutoff of an A(660) of 0.2, specificity would have ranged from 96.2 to 98.9% depending on specimen type, sex, and presence of symptoms. By employing the equivocal zone-retesting algorithm, specificity increased to 98.6 to 99.9% with little effect (0.1 to 4.9% decrease) on sensitivity in most specimen types, enabling the test to achieve a positive predictive value of at least 90% in populations with a prevalence of 4% or higher. In lower-prevalence populations, the test could be used to screen for presumptive infections that would have to be confirmed by an independent test.

Self-collection of vaginal swabs for the detection of Chlamydia, gonorrhea, and trichomoniasis: opportunity to encourage sexually transmitted disease testing among adolescents

BACKGROUND

Many sexually transmitted diseases (STDs) are prevalent among adolescents, yet compliance to undergo STD testing by this population is suboptimal. Efforts to enhance compliance with testing among at-risk youth are needed.

GOAL

To determine the feasibility and acceptability of self-collection of vaginal swabs for the detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis among high-school students attending a school health clinic.

STUDY DESIGN

Enrolled in the study were 228 female students between the ages of 15 and 19 years. Each student self-collected a single vaginal swab that was tested for C trachomatis, N gonorrhoeae, and T vaginalis by polymerase chain reaction amplification. Acceptability of self-collection of vaginal swabs was assessed.

RESULTS

The prevalence of any STD was 18%. Trichomoniasis, chlamydia, and gonorrhea were diagnosed in 10%, 8%, and 2% of students, respectively. Nearly 13% of females who had never previously had a gynecologic examination tested positive for an STD, and 51% of infected students would not have pursued testing by traditional gynecologic examination if self-collection was not offered. Self-collection of vaginal swabs was almost uniformly reported as easy to perform (99%) and preferable to a gynecologic examination (84%). Nearly all (97%) stated that they would undergo testing at frequent intervals if self-testing were available.

CONCLUSIONS

Self-collected vaginal swabs for STD testing can be easily implemented in a high-school setting with high acceptability among students, enabling the detection of many STDs that would otherwise remain undetected and untreated.

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

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

Comparison between the LCx Probe system and the COBAS AMPLICOR system for detection of Chlamydia trachomatis and Neisseria gonorrhoeae infections in patients attending a clinic for treatment of sexually transmitted diseases in Amsterdam, The Netherlands

Two assays for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae were compared: the LCx Probe system (the LCx system; Abbott Diagnostic Laboratories, North Chicago, Ill.) and the COBAS AMPLICOR C. trachomatis/N. gonorrhoeae system (the COBAS AMPLICOR system; Roche Diagnostic Systems, Branchburg, N.J.). Endocervical swab specimens, male urethral swab specimens, and female and male urine specimens were collected from 503 female and 498 male visitors attending a sexually transmitted diseases clinic in Amsterdam, The Netherlands. Prevalences for C. trachomatis were 12.5% (63 of 503) and 10.0% (50 of 498) in females and males, respectively. The prevalences for N. gonorrhoeae were 1.2% (6 of 503) and 4.2% (21 of 498) in females and males, respectively. Both assays showed high values for sensitivity and specificity with regard to the detection of C. trachomatis in endocervical swab specimens, male urethral swab specimens, and female and male urine specimens. The sensitivities for the LCx system were 92.1, 90.0, 88.9, and 94.0% for each type of specimen, respectively; and the sensitivies for the COBAS AMPLICOR system were 96.8, 98.0, 82.5, and 92.0% for each type of specimen, respectively. Specificities ranged between 98.4 and 100%. The sensitivity of the LCx system for the detection of N. gonorrhoeae was 100% for female cervical swab and urine specimens and male urethral swab specimens, while for male urine specimens the sensitivity was 95.2%; the specificity was 100% for all types of specimens. For the detection of N. gonorrhoeae by the COBAS AMPLICOR assay, the sensitivity for female cervical swab and male urethral swab specimens was 100%, that for female urine specimens was 66.7%, and that for male urine specimens was 95.2%. However, the predictive values of a positive test for female cervical swab specimens and urine specimens were 31.6 and 36.4%, respectively. Sequence analysis of the amplimers obtained by an in-house 16S rRNA PCR of the solely COBAS AMPLICOR system-positive swab specimens revealed neither N. gonorrhoeae nor other Neisseria spp. The COBAS AMPLICOR assay was considered not suitable for screening for infections with N. gonorrhoeae. If this assay is used for detection of N. gonorrhoeae, confirmation of positive results by a reliable test is mandatory.

Reproducibility problems with the Abbott laboratories LCx assay for Chlamydia trachomatis and Neisseria gonorrhoeae

This study demonstrates that significant reproducibility problems can occur during routine use of the Abbott Laboratories LCx assay for Chlamydia trachomatis and Neisseria gonorrhoeae. These problems can go undetected by the quality control procedures outlined in the manufacturer's package insert. We outline here procedures for detecting and preventing contamination and reproducibility problems.

The Use of Molecular Techniques for the Diagnosis and Epidemiologic Study of Sexually Transmitted Infections

Molecular diagnostic tests are more sensitive and, in many cases, more specific than conventional laboratory methods for the detection of sexually transmitted infections. Here, we review recently developed molecular methods for the diagnosis and subtyping of the most common sexually transmitted infections: infections caused by Chlamydia trachomatis, Neisseria gonorrhoeae, human papillomavirus, Trichomonas vaginalis, and the agents of genital ulcer disease (Haemophilus ducreyi, herpes simplex virus, Treponema pallidum, and Calymmatobacterium granulomatis). We also provide an overview of the laboratory diagnostic tests and clinical specimens to use when infection with these agents is suspected.

Pooling of urine samples for screening for Neisseria gonorrhoeae by ligase chain reaction: accuracy and application

The accuracy of detection of genital Neisseria gonorrhoeae infection in pooled urine samples by ligase chain reaction (LCR) was examined in three populations. Firstly, urine specimens from 300 female military recruits (FMR) were tested by LCR individually and in pools of four and six. Secondly, 300 urine specimens from middle-school students (MSS) were tested individually by LCR, and then the processed specimens were stored frozen for subsequent testing in pools of 4 and 10. Thirdly, 600 frozen urine specimens from high-school students (HSS) were tested by using the LCR pooling algorithm, i.e., testing processed specimens in pools of four in one test unit dose, and retesting individual specimens from positive pools. Finally, the pooling algorithm results were compared to culture results for a subset of 344 students from the original 600 HSS from whom cervical or urethral samples were taken at the discretion of the school nurse practitioners. Compared to individual testing of specimens by LCR in the FMR population, the pooling-by-four algorithm was 100% sensitive (5 of 5) and 100% pool specific (70 of 70), and the pool-by-six algorithm was 100% sensitive (5 of 5) and 100% pool specific (45 of 45). In the MSS population, the pool-by-4 algorithm was 95.8% sensitive (23 of 24) and 100% (52 of 52) pool specific, and the pool-by-10 algorithm was 95.8% sensitive (23 of 24) and 100% (17 of 17) pool specific. In the subset of 344 HSS from whom endocervical or urethral specimens were collected for culture, 31 were positive by LCR in urine and 26 were positive by culture. After results discrepant between culture and LCR were adjudicated by a confirmatory LCR test, the pooling algorithm was 93.8% (30 of 32) sensitive and 99.7% (311 of 312) specific. Culture from these 344 HSS was 81.3% (26 of 32) sensitive. The pooling algorithm reduced the cost of the N. gonorrhoeae LCR assay by 60% compared to individual testing of the HSS specimens and was both sensitive and specific.

Detection of Neisseria gonorrhoeae infection by ligase chain reaction testing of urine among adolescent women with and without Chlamydia trachomatis infection

BACKGROUND AND OBJECTIVES

Culture, the conventional method for detection of Neisseria gonorrhoeae, requires invasive sampling and stringent specimen transport conditions. The recently developed ligase chain reaction test (LCR; Abbott Laboratories; North Chicago, IL) allows noninvasive sampling and stable transport conditions, but has not been evaluated with specimens from adolescent populations.

GOAL OF THIS STUDY

To perform a comparative evaluation of a commercial LCR test and culture for the diagnosis of N. gonorrhoeae in adolescent women.

STUDY DESIGN

Urine and endocervical swab specimens from 330 teenage women seen in two public health adolescent clinics were tested by LCR and culture. For resolution of discordant results, a polymerase chain reaction (PCR) test was developed that directly amplifies N. gonorrhoeae DNA from urine samples processed for LCR.

RESULTS

Thirty-one of 330 (9.4%) cervical specimens were culture-positive for N. gonorrhoeae, and 30 of 330 (9.1%) urine specimens were positive by LCR. After resolution of 13 discordant results, the sensitivity, specificity, and positive and negative predictive values of LCR for urine were 88.2%, 100%, 100%, 98.7%, respectively, and for culture of endocervical specimens were 82.3%, 98.9%, 90.3% and 98%, respectively.

CONCLUSIONS

Although more expensive than culture, LCR offers a sensitive means for the detection of N. gonorrhoeae in urine samples and may be useful for this purpose in settings where pelvic examinations are difficult to perform and simultaneous detection of N. gonorrhoeae and Chlamydia trachomatis is advantageous.

Urethritis. Diagnosis of nongonococcal urethritis

Nongonococcal urethritis (NGU) frequently occurs in men after infection of the lower genital tract with a genital pathogen and is mostly associate with complaint of a scanty, thin discharge and urinary symptoms. Management of NGU includes clinical examination, microbiological diagnosis of genital pathogens, and efficient treatment as well as contact tracing. Diagnosis, especially of the Chlamydia trachomatis, the most frequent cause of NGU, has improved by using amplification assays for the detection of DNA or rRNA. These new methods have the advantage of a higher sensitivity especially for specimens with a low number of infectious agents. In addition, they enable the use of urine as a noninvasive specimen type.

Detection of GB virus C by the RT-PCR LCx system

The recent publication of representative genomic sequences of GBV-C has permitted the selection of PCR primers for detection of GBV-C in clinical samples by PCR techniques. Traditional amplification methodologies which couple reverse transcription polymerase chain reaction (RT-PCR) and Southern blot detection are slow, cumbersome, and can be technique dependent. This has hampered studies to determine the clinical significance of GBV-C. We report the selection of highly conserved PCR primers and a probe useful for semi-automated RT-PCR using the Abbott LCx system. This adaptation of the LCx system expands its capabilities to include the detection of RNA by RT-PCR, in addition to DNA detection by ligase chain reaction (LCR).

Gonococcal arthritis

Disseminated gonococcal infection is the most common systemic complication of acute gonorrhea and occurs in 0.5% to 3.0% of patients with untreated mucosal infection. It is also the most common cause of septic arthritis in patients less than 30 years of age. Fortunately, the incidence of gonorrhea is decreasing dramatically in the United States and Western Europe, although it is still high in developing countries. Increasing resistance to antibiotics requires continuous surveillance of antimicrobial susceptibilities to determine the efficacy of current therapeutic measures.