Second- and third-generation commercial Neisseria gonorrhoeae screening assays and the ongoing issues of false-positive results and confirmatory testing

Maximizing the Neisseria gonorrhoeae confirmatory rate and the genotypic detection of ciprofloxacin resistance for samples screened with cobas CT/NG

“…We demonstrate that the c6800 followed by the MP96-RP-GC testing is an improved supplemental testing method compared to c4800-RP-GC with a 100% confirmatory rate for urogenital samples and 93.6% for extragenital samples. As with our previous study and others ( 7 , 11 ), we conclude that supplemental testing is not required for c6800 for urogenital samples, but oropharyngeal samples should undergo secondary testing, in line with current Australian and UK guidelines ( 5 , 10 ). At the time of our previous study, the US version of the c6800 CTNG test did not have an oropharyngeal or anorectal claim, whereas the CE/IVD marked kits approved for use in Australia and the UK were approved for use for these sample types.…”

“…The problem has been most pronounced in testing oropharyngeal swabs, where commensal Neisseria species are ubiquitous ( 3 – 5 ). Earlier generation commercial assays lacked specific claims for testing oropharyngeal samples; however, third-generation commercial NG-NAATs have progressed to include performance claims for extragenital sites, such as oropharyngeal and anorectal swabs ( 2 , 6 , 7 ).…”

“…Our laboratory recently evaluated two versions of the cobas CT/NG assay (Roche Molecular Systems Inc., Branchburg, NJ, USA) using the cobas 4800 (c4800) and cobas 6800 (c6800) testing platforms. We showed that supplemental confirmatory testing may not be required for urogenital sites but is warranted for oropharyngeal samples for both assays owing to suboptimal confirmation rates ( 7 ). Another recent c6800 study has shown suboptimal confirmatory rates for oropharyngeal samples and advocated secondary testing for oropharyngeal samples in line with the UK guidelines ( 11 ).…”

“…This study was prompted by our previous concerns relating to suboptimal oropharyngeal confirmatory rates with an in-house supplemental assay detecting opa and porA ( 7 ). The ResistancePlus GC assay (RP-GC) (SpeeDx, Eveleigh, NSW, Australia) is a commercial supplemental test that simultaneously detects NG (dual target detection of opa and porA ), the gyrA 91S (wild type), or the gyrA 91F mutation associated with resistance to ciprofloxacin.…”

Clinical performance of four multiplex real-time PCR kits detecting urogenital and sexually transmitted pathogens

“…On the other hand, if the reference assay presents a lack of specificity, there is a risk of underestimation of PPA. Whereas a lack of specificity was reported using cobas 4800 for N. gonorrhoae in oropharyngeal specimens [24], performance seemed better using cobas 6800 [13] but might remain insufficient. A third assay and/or Sanger DNA sequencing would have helped to resolve discordant samples but no original sample was left.…”