Evaluation of Self-Collected Glans and Rectal Swabs from Men Who Have Sex with Men for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by Use of Nucleic Acid Amplification Tests

Abstract

Self-collected glans and rectal swab specimens from men who have sex with men (MSM) may be appropriate, convenient specimens for testing. We evaluated the use of self-collected swabs for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae by a transcription-mediated amplification test (AC2; Aptima Combo 2; Gen-Probe Inc.) and a strand displacement amplification test (SDA; ProbeTec; Becton Dickinson Co.) in MSM seen at the city sexually transmitted disease clinic in San Francisco, CA. For the glans swab specimen, subjects enrolled early in the study rolled a Dacron swab across the meatus three times (method 1). A slightly more invasive procedure was performed later in the study: the subjects inserted the swab 1/4 in. into the urethra, rotated the swab, and then withdrew the swab (method 2). MSM self-collected a rectal swab specimen and also provided first-catch urine (FCU). Additional rectal swab samples were then obtained by the clinician. For the detection of C. trachomatis and N. gonorrhoeae, all swabs were evaluated by AC2 and SDA, FCU was tested by AC2, and the clinician-collected rectal swabs were cultured. A rectal true-positive (TP) result was defined as a culture-positive result for C. trachomatis or N. gonorrhoeae, two or more positive nucleic acid amplification test (NAAT) results, or a single NAAT-positive result confirmed by an alternate amplification method (the Aptima C. trachomatis or N. gonorrhoeae test). A glans TP result was defined as a positive result for FCU, positive results for both glans specimens (one tested by AC2 and one tested by SDA), or a positive result for a single glans specimen confirmed by an alternate amplification method. The prevalence rates of C. trachomatis and N. gonorrhoeae by testing of FCU were 6.8% (60/882 specimens) and 12.2% (108/882 specimens), respectively. Mixed results were obtained with the glans swab: N. gonorrhoeae detection by AC2 and SDA (method 1) had the best performance (sensitivities, >92%) with samples from a population with a higher prevalence of infection, but their performance for the detection of C. trachomatis was poor and varied by collection method (sensitivities, 56 to 68%). The prevalence rates of C. trachomatis and N. gonorrhoeae in the rectum were 7.3% (66/907 specimens) and 9.4% (83/882 specimens), respectively. The sensitivities of the tests with self-collected and clinician-collected rectal swab specimens were comparable (for C. trachomatis, 41% and 44%, respectively, by SDA and 82% and 71%, respectively, by AC2; for N. gonorrhoeae, 77% and 68%, respectively, by SDA and 84% and 78%, respectively, by AC2). AC2 and SDA were far superior to culture for the detection of C. trachomatis and N. gonorrhoeae in the rectum, with both tests detecting at least twice as many infections. While we found self-collected rectal swabs from MSM to be valid specimens for testing, the sensitivities of the tests with glans swab specimens were disappointing except for those from patients with symptomatic N. gonorrhoeae infections. Self-collected gla...

Performance of the GeneXpert CT/NG Assay Compared to That of the Aptima AC2 Assay for Detection of Rectal Chlamydia trachomatis and Neisseria gonorrhoeae by Use of Residual Aptima Samples

“…A similar study using the same assays found respective sensitivities of 63% and 93% for C. trachomatis and 78% and 93% for N. gonorrhoeae (13). Neither of these two studies suggested that there was a significant problem with cross-reactivity of nongonococcal Neisseria species, with both reporting specificities in excess of 99.3% (12,13).…”

“…Because of this, user verification is necessary to provide data to support their use. Few studies have evaluated the performance of NAATs for use with rectal samples; however, one such study tested self-collected rectal swabs with the Becton, Dickinson ProbeTec and Gen-Probe Aptima Combo2 assays (12). Based on a composite gold standard of culture or agreement in two or more NAATs, the authors found respective sensitivities of 77.1% and 84.3% for C. trachomatis and 40.9% and 81.8% for N. gonorrhoeae.…”

“…In the United Kingdom, 82% of sexual health clinics offer asymptomatic MSM screening by NAATs for chlamydia, and 23% are offered NAATs for gonorrhea (2). Several studies using NAATs for the detection of N. gonorrhoeae and C. trachomatis from rectal swab samples have shown a higher burden of disease than would have been detected with traditional assays, including culture (1,6,(11)(12)(13)(14)(15).…”

“…In the United Kingdom, 82% of sexual health clinics offer asymptomatic MSM screening by NAATs for chlamydia, and 23% are offered NAATs for gonorrhea (2). Several studies using NAATs for the detection of N. gonorrhoeae and C. trachomatis from rectal swab samples have shown a higher burden of disease than would have been detected with traditional assays, including culture (1,6,(11)(12)(13)(14)(15).Despite a high prevalence of self-reported anal sex in the general population and some high-risk groups, there are no commercially available tests for chlamydia or gonorrhea that have regulatory approval for use with rectal swab samples (1,5,9,14). Problems of cross-reactivity with nongonococcal Neisseria species, which may frequently be found in the lower gastrointestinal tract, may have dissuaded commercial manufacturers from seeking regulatory approval for this sample type.…”

Chlamydia trachomatis infection prevalence and serovar distribution in a high-density urban area in the north of Italy

“…Nowadays, NAATs have become the reference method for CT detection in both urogenital and extra-genital samples, representing a reliable, fully automated, easy-to-use, highthroughput method (Moncada et al, 2009;Bachmann et al, 2010).…”