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

Abstract

c Triple-site testing (using pharyngeal, rectal, and urethral/first-void urine samples) for Neisseria gonorrhoeae and Chlamydia trachomatis using nucleic acid amplification tests detects greater numbers of infections among men who have sex with men (MSM). However, triple-site testing represents a cost pressure for services. MSM over 18 years of age were eligible if they requested testing for sexually transmitted infections (STIs), reported recent sexual contact with either C. trachomatis or N. gonorrhoeae, or had symptoms of an STI. Each patient underwent standard-of-care (SOC) triple-site testing, and swabs were taken to form a pooled sample (PS) (pharyngeal, rectal, and urine specimens). The PS was created using two methods during different periods at one clinic, but we analyzed the data in combination because the sensitivity of the two methods did not differ significantly for C. trachomatis (P ‫؍‬ 0.774) or N. gonorrhoeae (P ‫؍‬ 0.163). The sensitivity of PS testing (92%) was slightly lower than that of SOC testing (96%) for detecting C. trachomatis (P ‫؍‬ 0.167). For N. gonorrhoeae, the sensitivity of PS testing (90%) was significantly lower than that of SOC testing (99%) (P < 0.001). When pharynx-only infections were excluded, the sensitivity of PS testing to detect N. gonorrhoeae infections increased to 94%. Our findings show that pooling of self-taken samples could be an effective and cost-saving method, with high negative predictive values. (Interim results of this study were presented at the BASHH 2013 summer meeting.) I n the United States and Europe, genital Chlamydia trachomatis and Neisseria gonorrhoeae are the most prevalent bacterial sexually transmitted infections (STIs). In the United Kingdom, rates of gonorrhea and chlamydia among men who have sex with men (MSM) continue to rise (1), while studies highlight increases in the numbers of HIV-positive and HIV-negative MSM reporting high-risk sexual behavior since the advent of combination antiretroviral therapy (cART) (2-4).Coinfection with an STI and HIV has been shown to increase HIV transmission in epidemiological studies (5-7). Concomitant genital infections have been shown to increase shedding of HIV in the genital tract, in both vaginal secretions and seminal fluid (8, 9). Rectal C. trachomatis/N. gonorrhoeae infections have been associated with HIV acquisition in MSM (10), and it is plausible that they may also enhance HIV transmission.Nucleic acid amplification tests (NAATs) are being used increasingly to screen MSM for pharyngeal and rectal C. trachomatis/N. gonorrhoeae infections, in addition to the use of urethral or first-void urine (FVU) samples, and the use of NAATs is now recommended in national guidelines (11). While there are no NAATs licensed for use with extragenital specimens, several studies have demonstrated that NAATs perform well for the detection of both pharyngeal and rectal C. trachomatis/N. gonorrhoeae infections in . Studies evaluating the performance of these testing methodologies have demonstrated sensitivities and sp...

Detection of Neisseria gonorrhoeae and Chlamydia trachomatis from pooled rectal, pharyngeal and urine specimens in men who have sex with men

“…Pooling of urine specimens from multiple individuals has been shown to be sensitive and specific for CT testing15 16 and the effectiveness of pooling specimens from different anatomical sites within an individual for CT and NG detection has been demonstrated previously 11. These workers tested throat and rectal swabs and urine samples in MSM using the AC2 assay and demonstrated high negative predictive values for pooled sample testing.…”

“…It is possible that the dilutional effect of the urine in the pooled specimens was responsible for the apparent reduced sensitivity for the solitary rectal CT infections. Sultan et al 11 also found single site infections accounted for almost all of their missed CT and NG infections with pooled specimen testing, but found the throat swabs were less sensitive than the rectal swabs. Direct comparison of pooled testing and individual specimen testing using the GeneXpert would help address this.…”

“…There are limited data on the use of NAATs for the detection of CT and NG using pooled specimens. Sultan et al 11 studied pharyngeal, rectal and urine specimens in MSM by comparing single sample analysis with pooled remaining samples using the Aptima Combo 2 TMA assay (AC2) (Hologic, San Diego, CA, USA). For their cohort of 164 CT and 288 NG detections from single sample testing they found the sensitivity of pooled sampling to be slightly lower but not significantly different (p=0.167) for CT (92% vs 96%); however, pooled sampling was significantly lower (p<0.001) for NG (90% vs 99%), resulting in 13 missed CT infections and 31 missed NG infections.…”

2016 United Kingdom national guideline on the sexual health care of men who have sex with men

“…National data from the Netherlands suggests that a majority of chlamydial and gonococcal infections in MSM would be missed if extragenital sites are not tested (77), although there is no published cost effectiveness data to compare this strategy with history-directed testing. Pooling of samples from pharynx, urine and rectum may be a means of reducing costs (78). It is desirable that hepatitis B vaccination is offered in all settings but the advantages of expanding the availability of HIV and STI testing should not be lost if this is not practicable in outreach situations.…”

Missed Opportunities of Chlamydia and Gonorrhea Detection When Not Using Extra Genital Screening Among Males

“…Extra genital screening tests patients in their genital, urethral, and pharyngeal sites. Although urine is most widely used to test for CT/GC infection, it is still recommended to test all three sites as an individual's sexual practices can place them at greater risk for infection, depending on the type of sex they are having (13,15) . Information on the underlying disparities regarding prevalence and incidence of disease is necessary for bridging the gap in services.…”