Take three, test one: a cross-sectional study to evaluate the molecular detection of Chlamydia trachomatis and Neisseria gonorrhoeae in pooled pharyngeal, anorectal and urine samples versus single-site testing among men who have sex with men in Belgium

Searching for sexually transmitted infections by midstream urine pooling after exclusion of urinary tract infection: A cost-effectiveness analysis

We aimed to evaluate the cost-effectiveness of screening for sexually transmitted infections (STI), Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, and Trichomonas vaginalis in patients with suspected urinary tract infection (UTI) but negative urine cultures, using a pooled sampling method. A cohort of 200 patients was analyzed. A decision tree model based on cost-effectiveness was used to evaluate the following five diagnostic strategies: (A) no screening;(B) screening only men;(C) screening only women;(D) screening men and women with high leukocyte counts (>70cells/µL);(E) screening all men and women. The pooling method reduced reagent testing costs by 75 %. The most cost-effective strategy was screening men and women with high leukocyte counts, yielding an incremental cost-effectiveness ratio of 489.05euros. STI screening using pooled midstream urine samples in patients with suspected UTI and negative urine cultures is cost-effective, particularly when targeting individuals with high leukocyte counts. This approach optimizes resource use and improves early STI detection.

Self-sampling with oral rinse to detect oropharyngeal Neisseria gonorrhoeae among men who have sex with men: results from an exploratory study in Belgium (the SSONG Study)

OBJECTIVES

We aimed to assess whether a self-collected oral rinse was non-inferior to clinician-collected oropharyngeal swabs to detect Neisseria gonorrhoeae (Ng) using culture and nucleic acid amplification tests (NAAT) among men who have sex with men (MSM), and whether Ng may still be detected in oral rinses for a minimum of 5 days after collection.

METHODS

MSM with a positive Ng result in an oropharyngeal or pooled sample (oropharynx, urethra and anorectum) were approached. Clinician-collected oropharyngeal swabs and oral rinses (15 mL sterile water) were taken. Ng culture and NAAT (Abbott 2000m RealTime System CT/NG assay and in-house PCR) were performed. Diagnostic accuracy was assessed using sensitivity and specificity, and agreement between both techniques using Cohen's kappa statistic. Aliquots of positive oral rinses were left at room temperature for a minimum of 5 days and reanalysed using NAAT. Lastly, participants filled in a questionnaire to explore perceptions of both methods.

RESULTS

We included 100 participants between June 2022 and October 2023. 45 individuals (45 of 100) had a positive Ng result in either the oral rinses (42 of 45, 93%) or the swabs (36 of 45, 80%). Sensitivity was higher for oral rinses than swabs (sensitivity=0.93/0.80, specificity=1.0/1.0, respectively) and agreement between both techniques was good (kappa=0.75, p<0.001). Of the 42 positive oral rinses, 37 remained positive after a minimum of 5 days (88.1%). Using culture, 18 individuals had a positive Ng result in either the oral rinses (8 of 18, 44%) or the swabs (16 of 18, 88%). Most participants found the oral rinse easy or very easy to use and would be willing to use the oral rinse for home-based sampling.

CONCLUSION

We detected more oropharyngeal Ng infections via NAAT using oral rinses than swab samples. However, swabs were better than oral rinses for culturing Ng. Oral rinses might allow for home-based self-sampling to detect oropharyngeal Ng.

Patterns of Chlamydia trachomatis and Neisseria gonorrhoeae in different anatomical sites among Pre-Exposure Prophylaxis (PrEP) users in Brazil

BACKGROUND

The presence of untreated sexually transmitted infections (STIs) significantly increases the chance of acquiring HIV. In Brazil, testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) among Pre-Exposure Prophylaxis (PrEP) users is insufficient, and syndromic treatment is a priority in clinical practice. Multi-site testing for CT/NG improves thescreening of asymptomatic cases and ensures timely treatment. Therefore, it is essential for HIV prevention. This study aims to test the importance of two-site testing for better screening of these pathogens and to determine whether the presence of symptoms is an indicator of CT/NG infection.

METHODS

This is a cross-sectional study carried out in four public infectious diseases clinics in São Paulo State, Brazil between January of 2022 and March of 2023. All participants had an anal swab and a first-pass or mid-stream urine collected for CT/NG analysis by Polymerase chain reaction (PCR). Data about sociodemographic, sexual behavioural and clinical aspects were collected. Pathway analysis was used to examine the direct and indirect relationships between variables according to the theoretical model.

RESULTS

We screened 171 PrEP users which had two samples collected, resulting in 342 samples. Comparing the anatomic sites, the urine samples showed lower sensitivity for CT and NG than anal samples. Gonorrhoea was directly linked to lower age (β= -0.161, p = 0.001). Time of PrEP use was directly associated with CT infection (β = 0.202; p = 0.042) and inversely associated with dysuria (β= -0.121, p = 0.009). Lower occurrence of yellow-green secretion was linked to detection of CT (β= -0.089, p = 0.005) and NG (β= -0.048, p = 0.002) infections. Foul-smelling discharge was directly associated with CT (β = 0.275, p = 0.004) and NG (β = 0.295, p = 0.037) infection.

CONCLUSION

The symptoms are a bad indicator of CT and NG infection, and the screening must be done in more than one site since most of the positive results would be missed if only urines were tested. In the case of testing only one anatomical site, specifically the urethra, the CT/NG incidence and prevalence would be underestimated. The two-sites testing improves detection rates of CT/NG, and PrEP follow-up benefits people offering STI testing.

Pooled Pharyngeal, Rectal, and Urine Specimens for the Point-of-Care Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by Lay Providers in Key Population-Led Health Services in Thailand

Routine testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) in people with heightened risk is lacking in Thailand. This study aimed to assess the performance of the Cepheid Xpert CT/NG assay, conducted by key population (KP) lay providers, for CT and NG detection on single-site and pooled specimens from the pharynx, rectum, and urine. Between August and October 2019, 188 men who have sex with men and 11 transgender women were enrolled. Participants collected urine specimens while trained KP lay providers obtained pharyngeal and rectal swabs. Compared to single-site testing with the Abbott RealTime CT/NG assay by medical technologists, the Xpert assay missed one pharyngeal NG infection out of 199 single-site specimens, giving a 93.3% sensitivity for pharyngeal NG and one missed pharyngeal NG infection out of fifty pooled specimens, giving an 88.9% sensitivity for pharyngeal NG. There was no discrepancy between the two assays for CT detection. The Cohen's Kappa coefficient of pooled specimen testing by the Xpert was 0.93 for NG and 1 for CT when compared to single-site testing by Abbott. Implementing pooled specimen testing by KP lay providers can be a cost-saving strategy to enhance the uptake of CT/NG services for populations facing increased risk.

Using pooled urogenital, anorectal and oropharyngeal specimens to detect Chlamydia trachomatis and Neisseria gonorrhoeae among men who have sex with men in China: a multisite diagnostic accuracy study

OBJECTIVES

Screening for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) at both urogenital and extragenital sites has been recommended in many countries. Testing of the infections using pooled specimens from urogenital and extragenital sites offer the opportunity to shorten the testing time and reduce the testing cost. Ex-ante pooling is placing the original single-site specimens in a tube with transport media, while ex-post pooling is making a pool of the transport media from both anorectal and oropharyngeal specimens and the urine. This study aimed to conduct a multisite performance evaluation of two pool-specimen approaches (ex-ante and ex-post) in detection of CT and NG using the Cobas 4800 platform among men who have sex with men (MSM) in China.

DESIGN

Diagnostic accuracy study.

SETTING, PARTICIPANTS AND OUTCOME MEASURES

Participants were recruited from MSM communities at six cities in China. Two oropharyngeal and anorectal swabs collected by clinical staff and 20 mL first-void urine collected by the participant himself were used for evaluating sensitivity and specificity.

RESULTS

A total of 1311 specimens were collected from 437 participants in six cities. The sensitivities of ex-ante pooling approach as compared with single-specimen approach (reference standard) were 98.7% (95% CI, 92.7% to 100.0%) for detection of CT and 89.7% (95% CI, 75.8% to 97.1%) for NG, and the specificities were 99.5% (95% CI, 98.0% to 99.9%) and 98.7% (95% CI, 97.1% to 99.6%), respectively. The sensitivities of ex-post pooling approach were 98.7% (95% CI, 92.7% to 100.0%) for CT and 100.0% (95% CI, 91.0% to 100.0%) for NG, and the specificities were 100.0% (95% CI, 99.0% to 100.0%) and 100.0% (95% CI, 99.1% to 100.0%), respectively.

CONCLUSIONS

The ex-ante and ex-post pooling approaches show good sensitivity and specificity in detecting urogenital and extragenital CT and/or NG, indicating that these approaches can be used in epidemiological surveillance and clinical management of CT and NG infections, particularly among MSM population.

Pooling Rectal, Pharyngeal, and Urine Samples to Detect Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycoplasma genitalium Using Multiplex Polymerase Chain Reaction Is as Effective as Single-Site Testing for Men Who Have Sex With Men

Background

Screening for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) at pharyngeal, urogenital, and anorectal sites is recommended for men who have sex with men (MSM). Pooling samples is a promising technique, but no data are available when pooled screening also includes Mycoplasma genitalium (MG). The main objective of this study was to examine the sensitivity of pooled samples for detecting CT, NG, and MG in MSM using nucleic acid amplification versus single-site testing.

Methods

In this multicenter study, MSM with a positive result for CT, NG, or MG were recalled to the clinic for treatment and were asked to participate in this study. Separate samples were sent to a central virological department that proceeded to form the pooled samples. Testing was performed using the multiplex real-time polymerase chain reaction Allplex STI Essential Assay (Seegene, Seoul, Korea), which can simultaneously detect 7 pathogens.

Results

A total of 130 MSM with at least 1 positive test for CT, NG, or MG were included. A total of 25.4% had a coinfection. The sensitivities of pooled-sample testing were 94.8% for CT, 97.0% for NG, and 92.3% for MG. Pooling failed to detect 8 infections, but pooled-sample analysis missed detecting only samples with a low bacterial load (cycle threshold >35).

Conclusions

Pooling samples from MSM to detect CT, NG, and MG is as sensitive as individual-site testing for these 3 pathogens using the Allplex assay. Missed infections with a very low bacterial load could have a low impact on further transmission.

Clinical Trials Registration. NCT03568695.

Evaluating specimen pooling for Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycoplasma genitalium screening in asymptomatic men who have sex with men

BACKGROUND

Screening for Neisseria gonorrhoeae and Chlamydia trachomatis is recommended for individuals at high-risk for sexually transmitted infections (STIs), while the role of Mycoplasma genitalium screening is still unclear. We evaluated whether specimen pooling is an effective alternative for sexually transmitted infection testing during resource shortages.

METHODS

This 2-year prospective study enrolled 135 asymptomatic patients from a community outreach site who identified as men who have sex with men. Oropharyngeal, urine, and/or rectal swab specimens were pooled and tested using the Aptima Combo 2 assay for Neisseria gonorrhoeae and Chlamydia trachomatis. The Aptima Mycoplasma genitalium assay was performed on 34 patients whose specimens had sufficient sample volume for additional testing. Results from pooled specimens were compared to results obtained by individual-site testing.

RESULTS

The positive percent agreement (PPA) between pooled testing and individual-site testing was 93.8% and negative percent agreement (NPA) was 100% for Neisseria gonorrhoeae. For Chlamydia trachomatis, the PPA was 85.7% and NPA was 99.2%. A PPA of 72.7% and NPA of 95.7% were observed for Mycoplasma genitalium. Discrepancy analysis revealed the majority of false-negative pools were from failure to detect positive rectal samples.

CONCLUSIONS

Specimen pooling reduces sensitivity of the Aptima assays for Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma genitalium and thus should be used with caution.

Epidemiology of symptomatic infective anoproctitis in a population of men having sex with men (MSM)

PURPOSE

Anoproctitis due to Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are Sexual Transmitted Infections (STIs) reported in MSM population. This study describes clinical and microbiological epidemiology of infective anoproctitis in MSM population.

METHODS

All patients with symptomatic anoproctitis consulting at the proctology Institute of Saint-Joseph's Hospital, Paris, were included. Detection of CT/NG was performed by PCR GeneXpert^R and other STIs pathogens Mycoplasma sp., HSV, CMV and T. pallidum were detected by multiplex PCR Allplex (mPCR).

RESULTS

Symptoms most frequently reported were pain, rectal bleeding and purulent flow in 66%, 52% and 49% of cases, respectively. On the 311 rectal samples collected, 171 (55.2%) were positive to CT/NG. Among the 194 used for mPCR, 148 were positive to STIs pathogens (76.2%) including 106 samples (71.6%) positive in coinfections. Among NG infections, 22.6% of the strains were resistant to azithromycin and 26.8% to tetracyclines.

CONCLUSIONS

Anorectal infections in this MSM population showed a high prevalence of not only CT/NG but also other pathogens involved in STIs. The high level of coinfections confirms the requirement of accurate PCR tests to improve diagnosis. This study describing increasing antibiotic resistances for NG strains confirms the updating of international guidelines on antibiotic treatments recommendations.

Diagnosis and treatment of gonorrhoea: 2019 Belgian National guideline for primary care

OBJECTIVES

Gonorrhoea continues to be a public health concern in Belgium with pharyngeal and rectal infections increasing in persons with high-risk sexual behaviour. Belgian health care practitioners rely on international guidance when managing gonorrhoea resulting in non-adapted suboptimal care for the Belgian patient. This guideline will rectify this situation.

METHODS

This guideline was developed following an evidence-based approach and involving a guideline development group (GDG). Research questions were prioritised by the GDG and researchers conducted a systematic review of the evidence that was assessed using GRADE approach.

RESULTS

The guideline offers recommendations for gonorrhoea diagnosis, treatment and management for primary care professionals in Belgium and applies a risk group approach. This approach aims for improved identification of at-risk persons and targeted testing of at-risk groups; it includes behavioural questioning when deciding on diagnostic sampling and provides clear advice on treatment. The guideline defines when to add surveillance testing for antibiotic resistance, and what consists of good follow-up.

RESULTS

A concerted application of this guideline by all stakeholders in Belgium may result in improving the diagnosis of infections and eventually addressing the emerging multi-drug resistance.

Retrospective detection of asymptomatic monkeypox virus infections among male sexual health clinic attendees in Belgium

The magnitude of the 2022 multi-country monkeypox virus (MPXV) outbreak has surpassed any preceding outbreak. It is unclear whether asymptomatic or otherwise undiagnosed infections are fuelling this epidemic. In this study, we aimed to assess whether undiagnosed infections occurred among men attending a Belgian sexual health clinic in May 2022. We retrospectively screened 224 samples collected for gonorrhea and chlamydia testing using an MPXV PCR assay and identified MPXV-DNA-positive samples from four men. At the time of sampling, one man had a painful rash, and three men had reported no symptoms. Upon clinical examination 21-37 days later, these three men were free of clinical signs, and they reported not having experienced any symptoms. Serology confirmed MPXV exposure in all three men, and MPXV was cultured from two cases. These findings show that certain cases of monkeypox remain undiagnosed and suggest that testing and quarantining of individuals reporting symptoms may not suffice to contain the outbreak.

Pooled 3-Anatomic-Site Testing for Chlamydia trachomatis and Neisseria gonorrhoeae: A Systematic Review and Meta-Analysis

BACKGROUND

Pooled testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) may be a cost-saving solution to increase screening by simplifying testing procedures and reducing resource burdens. We conducted a systematic review and meta-analysis to examine the performance of pooled 3-anatomic-site testing (pharyngeal, rectal, and urogenital sites) for CT and NG in comparison with single-anatomic-site testing.

METHODS

We conducted a systematic literature search in PubMed, Embase, and Web of Science to identify original evaluation studies of the performance of pooled testing for CT and NG infections and identified 14 studies for inclusion. Each study was systematically evaluated for bias. We conducted bivariate fixed-effects and random-effects meta-analyses using a full Bayesian method of the positive percent agreement and negative percent agreement.

RESULTS

The combined positive percent agreement for CT was 93.11% (95% confidence interval [CI], 91.51%-94.55%), and the negative percent agreement was 99.44% (95% CI, 99.18%-99.65%). For NG, the combined positive percent agreement was 93.80% (95% CI, 90.26%-96.61%), and the negative percent agreement was 99.73% (95% CI, 99.30%-99.97%).

CONCLUSIONS

We found that pooled 3-anatomic-site tests performed similarly to single-anatomic-site tests for the detection of CT and NG. The pooled 3-anatomic-site tests have the added potential benefit of reduced cost and resource requirement, which could lead to improved testing access and screening uptake.

Diagnostic accuracy of pooling urine, anorectal, and oropharyngeal specimens for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae: a systematic review and meta-analysis

BACKGROUND

Screening for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) at genital and extragenital sites is needed for most key populations, but molecular diagnostic tests for CT/NG are costly. We aimed to determine the accuracy of pooled samples from multiple anatomic sites from one individual to detect CT/NG using the testing of a single sample from one anatomic site as the reference.

METHODS

In this systematic review and meta-analysis, we searched five databases for articles published from January 1, 2000, to February 4, 2021. Studies were included if they contained original data describing the diagnostic accuracy of pooled testing compared with single samples, resource use, benefits and harms of pooling, acceptability, and impact on health equity. We present the pooled sensitivities and specificities for CT and NG using a bivariate mixed-effects logistic regression model. The study protocol is registered in PROSPERO, an international database of prospectively registered systematic reviews (CRD42021240793). We used GRADE to evaluate the quality of evidence.

RESULTS

Our search yielded 7814 studies, with 17 eligible studies included in our review. Most studies were conducted in high-income countries (82.6%, 14/17) and focused on men who have sex with men (70.6%, 12/17). Fourteen studies provided 15 estimates for the meta-analysis for CT with data from 5891 individuals. The pooled sensitivity for multisite pooling for CT was 93.1% [95% confidence intervals (CI) 90.5-95.0], I²=43.3, and pooled specificity was 99.4% [99.0-99.6], I²=52.9. Thirteen studies provided 14 estimates for the meta-analysis for NG with data from 6565 individuals. The pooled sensitivity for multisite pooling for NG was 94.1% [95% CI 90.9-96.3], I²=68.4, and pooled specificity was 99.6% [99.1-99.8], I²=83.6. Studies report significant cost savings (by two thirds to a third).

CONCLUSION

Multisite pooled testing is a promising approach to improve testing coverage for CT/NG in resource-constrained settings with a small compromise in sensitivity but with a potential for significant cost savings.

Real-life occurrence of bacterial sexually transmitted infections among PrEP users: improving the diagnosis of Chlamydia trachomatis and Neisseria gonorrhoeae with multisite screening

PrEP users are under high risk for bacterial sexually transmitted infections (STI), including those caused by Treponema pallidum (Tp), Chlamydia trachomatis (Ct) and Neisseria gonorrhoeae (Ng). Ct and Ng screening at multiple anatomic sites may improve the diagnostic sensitivity among high-risk populations. We analyzed the prevalence and incidence of Ct, Ng, and Tp and investigated predictors of bacterial STI occurrence between January 2018 and November 2019 in a retrospective cohort of PrEP users in Sao Paulo, Brazil. We describe the frequency and percentage of Ct/Ng per anatomical site and calculate the percentage of missed diagnosis if molecular testing were applied only in symptomatic patients, or only in urine samples. Patients underwent syphilis testing every 3-4 months and Ct/Ng testing every 6 months. We included 413 PrEP users with a median age of 31 years. At baseline, 25% had a positive treponemal test and 7% had active syphilis; Ct and Ng were more frequently detected in the oropharynx and anus (6.4-6.9%) than in urine samples (0.7-2.6%). Twelve months after the onset of PrEP, the incidence of Tp, Ct and Ng was, respectively, 13.4%, 11.4% and 8.9%. During follow-up, 23 out of 33 Ct/Ng cases (69%, 95% CI 51-84) would have been missed if oropharynx and anus samples had not been tested. In addition, if only symptomatic cases had been tested, 30 out of 33 Ct/Ng cases (90%, 95% CI 75-98) would have been missed. Participants with incident STI had a higher baseline number of sexual partners and a longer follow-up. Our study reinforces that active and frequent screening for STI is a powerful strategy to improve the diagnostic sensitivity.

Swab-Yourself Trial With Economic Monitoring and Testing for Infections Collectively (SYSTEMATIC): Part 2. A Diagnostic Accuracy and Cost-effectiveness Study Comparing Rectal, Pharyngeal, and Urogenital Samples Analyzed Individually, Versus as a Pooled Specimen, for the Diagnosis of Gonorrhea and Chlamydia

BACKGROUND

Sexual history does not accurately identify those with extragenital Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT), so universal extragenital sampling is recommended. Nucleic acid amplification tests (NAATs) are expensive. If urogenital, plus rectal and pharyngeal, samples are analyzed, the diagnostic cost is trebled. Pooling samples into 1 NAAT container would cost the same as urogenital samples alone. We compared clinician triple samples analyzed individually with self-taken pooled samples for diagnostic accuracy, and cost, in men who have sex with men (MSM) and females.

METHODS

This was a prospective, convenience sample in United Kingdom sexual health clinic. Randomized order of clinician and self-samples from pharynx, rectum, plus first-catch urine (FCU) in MSM and vulvovaginal swabs (VVS) in females, for NG and CT detection.

RESULTS

Of 1793 participants (1284 females, 509 MSM), 116 had NG detected (75 urogenital, 83 rectum, 72 pharynx); 276 had CT detected (217 urogenital, 249 rectum, 63 pharynx). There was no difference in sensitivities between clinician triple samples and self-pooled specimens for NG (99.1% and 98.3%), but clinician samples analyzed individually identified 3% more chlamydia infections than pooled (99.3% and 96.0%; P = .027). However, pooled specimens identified more infections than VVS/FCU alone. Pooled specimens missed 2 NG and 11 CT infections, whereas VVS/FCU missed 41 NG and 58 CT infections. Self-taken pooled specimens were the most cost-effective.

CONCLUSIONS

FCU/VVS testing alone missed many infections. Self-taken pooled samples were as sensitive as clinician triple samples for identifying NG, but clinician samples analyzed individually identified 3% more CT infections than pooled. The extragenital sampling was achievable at no additional diagnostic cost to the FCU/VVS.

CLINICAL TRIALS REGISTRATION

NCT02371109.

The Performance of Pooled 3 Anatomic Site Testing for Chlamydia trachomatis and Neisseria gonorrhoeae Among Men Who Have Sex With Men and Transgender Women

BACKGROUND

Although molecular testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) is highly sensitive, the cost can be prohibitive. Those high costs are amplified when the recommended screening approach is used, which requires separate testing of specimens from 3 anatomic sites (rectal, pharyngeal and urogenital). Although individual molecular testing is standard of care, pooled testing may offer a cost-saving alternative.

METHODS

Using the Xpert® CT/NG assay (Cepheid, Sunnyvale, CA) we tested urine, rectal and pharyngeal swabs for CT and NG in a high-risk cohort of participants assigned male at birth who reported sex with other persons who were assigned male at birth. Remnant specimens (0.34 mL from each anatomic site) were combined to perform a single 'pooled' test. We calculated positive and negative percent agreement between the pooled testing results with standard of care Xpert CT/NG test results as the reference.

RESULTS

We conducted 644 pooled tests. Of those, 598 (92.3%) gave CT and NG results. The CT-positive and -negative percent agreement were 90.1% (95% confidence interval [CI], 80.7-95.9%) and 99.2% (98.1-99.8%), respectively. The NG-positive and -negative percent agreement were 96.2% (95% CI, 86.8-99.5%) and 99.8% (95% CI, 99.0-100%), respectively. Pooled testing identified 4 CT and 1 NG infections that were negative at all anatomic sites by individual testing.

CONCLUSIONS

Three-site pooled CT and NG testing performs similarly to single anatomic site testing among tests providing a valid result. Future cost analyses should evaluate the cost effectiveness of pooled 3-site testing to determine if such a strategy improves the feasibility and accessibility of molecular sexually transmitted infection testing.

Modified self-obtained pooled sampling to screen for Chlamydia trachomatis and Neisseria gonorrhoeae infections in men who have sex with men

OBJECTIVES

To assess whether pooled sample testing with nucleic acid amplification tests was a potential alternative to three single-site sample testing to screen for Chlamydia trachomatis and Neisseria gonorrhoeae infections in asymptomatic men who have sex with men.

METHODS

We prospectively compared pooled sample testing with single-site sample testing in asymptomatic MSM. Self-obtained paired rectal samples, one gargle sample and one first-void urine sample were collected from participants to generate two sets of samples: one for pooled sample testing and the other for single-site testing. We used modified pooled sampling, which is defined as the use of gargle samples, instead of swabs, for the pooled sample to test for pharyngeal infection.

RESULTS

This study included 513 MSM. The positive rates of C. trachomatis and N. gonorrhoeae were 20.3% and 11.7%, respectively, for single-site sample testing. Compared with the sensitivity of single-site testing as the gold standard, the sensitivities of pooled sample testing for C. trachomatis and N. gonorrhoeae were 94.2% (95% CI 88.0% to 97.3%) and 98.3% (95% CI 90.9% to 99.9%), respectively. The concordance rate and kappa coefficient were 98.3% (95% CI 96.7% to 99.2%) and 0.945 (95% CI 0.859 to 1.000), respectively, for C. trachomatis and 98.8% (95% CI 90.1% to 100%) and 0.943 (95% CI 0.857 to 1.000), respectively, for N. gonorrhoeae.

CONCLUSIONS

The modified pooled sampling had a comparably high consistency with single-site sample testing. The results strongly suggest that the gargle sample is suitable as a part of pooled sample for STI screening of C. trachomatis and N. gonorrhoeae.

To pool or not to pool? Screening of Chlamydia trachomatis and Neisseria gonorrhoeae in female sex workers: pooled versus single-site testing

OBJECTIVES

As Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are the most commonly reported STIs in Belgium and the majority of women infected are asymptomatic, targeted screening of patients in specified risk groups is indicated. To prevent long-term complications and interrupt transmission, extragenital samples should be included. As this comes with a substantial extra cost, analysis of a pooled sample from vaginal and extragenital sites could be a solution. In this study, we evaluated the feasibility of molecular testing for CT and NG in pooled versus single-site samples in a large cohort of female sex workers.

METHODS

Women were sampled from three anatomical sites: a pharyngeal, a vaginal and a rectal swab. Each sample was vortexed, and 400 µL of transport medium from each sample site was pooled into an empty tube. NAAT was performed using the Abbott RealTime CT/NG assay on the m2000sp/rt system.

RESULTS

We included 489 patients: 5.1% were positive for CT; 2.0% were positive for NG and 1.4% were coinfected, resulting in an overall prevalence of 6.5% (95% CI 4.5% to 9.1%) for CT and 3.5% (95% CI 2.0% to 5.5%) for NG. From the 42 patients positive on at least one non-pooled sample, only 5 gave a negative result on the pooled sample, resulting in a sensitivity of 94% (95% CI 79% to 99%) for CT and 82% (95% CI 57% to 96%) for NG. The missed pooled samples were all derived from single-site infections with low bacterial loads. The possibility of inadequate self-sampling as a cause of false negativity was excluded, as 4/5 were collected by the physician. Testing only vaginal samples would have led to missing 40% of CT infections and 60% of NG infections.

CONCLUSIONS

Pooling of samples is a cost-saving strategy for the detection of CT and NG in women, with minimal decrease in sensitivity. By reducing costs, more patients and more extragenital samples can be tested, resulting in higher detection rates.

Pooling Pharyngeal, Anorectal, and Urogenital Samples for Screening Asymptomatic Men Who Have Sex with Men for Chlamydia trachomatis and Neisseria gonorrhoeae

Screening for Chlamydia trachomatis and Neisseria gonorrhoeae at the pharyngeal, urogenital, and anorectal sites is recommended for men who have sex with men (MSM). Combining the three individual-site samples into a single pooled sample could result in significant cost savings, provided there is no significant sensitivity reduction. The aim of this study was to examine the sensitivity of pooled samples for detecting chlamydia and gonorrhea in asymptomatic MSM using a nucleic acid amplification test. Asymptomatic MSM who tested positive for chlamydia or gonorrhoea were invited to participate. Paired samples were obtained from participants prior to administration of treatment. To form the pooled sample, the anorectal swab was agitated in the urine specimen transport tube and then discarded. The pharyngeal swab and 2 ml of urine sample were then added to the tube. The difference in sensitivity between testing of pooled samples and individual-site testing was calculated against an expanded gold standard, where an individual is considered positive if either pooled-sample or individual-site testing returns a positive result. All samples were tested using the Aptima Combo 2 assay. A total of 162 MSM were enrolled in the study. Sensitivities of pooled-sample testing were 86% (94/109; 95% confidence interval [CI], 79 to 92%]) for chlamydia and 91% (73/80; 95% CI, 83 to 96%) for gonorrhea. The sensitivity reduction was significant for chlamydia (P = 0.02) but not for gonorrhea (P = 0.34). Pooling caused 22 infections (15 chlamydia and 7 gonorrhoea) to be missed, and the majority were single-site infections (19/22). Pooling urogenital and extragenital samples from asymptomatic MSM reduced the sensitivity of detection by approximately 10% for chlamydia but not for gonorrhea.