The reference test was the Aptima Combo 2® assay (from here referred to as Aptima), which utilizes transcription-mediated amplification (TMA) to amplify the target rRNA and uses a Dual Kinetic Assay to detect the amplicon. The Aptima assay detects a specific region of the 23S rRNA from CT and a specific region of the 16S rRNA from NG. Results from the Aptima test are routinely used by AHF for patient management and were communicated to the clinicians and participants. The standard of care at AHF currently does not include pharyngeal CT testing and therefore pharyngeal CT results were not available for analysis. Laboratory staff that performed the Aptima test were not aware of symptom status or results from the comparator test.
The Xpert® CT/NG assay (from here referred to as Xpert) is run on the GeneXpert® System and can be implemented in clinical settings without the need for central laboratory processing. That assay is run in approximately 90 minutes and results are displayed in tabular and graphic formats on a computer system. The GeneXpert® System has three main internal quality control mechanisms to ensure ideal test functioning and conditions.18 One of those internal quality control mechanisms is the sample adequacy control (SAC), which detects the presence of the gene encoding hydroxymethylbilane synthase (HMBS), a single-copy human cellular housekeeping gene, to monitor whether the sample contains human DNA. A negative SAC indicates that inadequate numbers of human cells were present in the sample, which can be due to sample degradation, insufficient mixing, or because of an inadequately collected specimen. The primers and probes in the Xpert CT/NG Assay detect chromosomal sequences in the CT and NG bacteria, with one target for CT and two different targets for NG. Both of the NG targets need to be positive for the Xpert CT/NG Assay to return a positive NG result. The testing methods occurred in accordance with the manufacturer directions. Xpert results were neither used for clinical management nor were communicated to the participants. Indeterminate Xpert test results were rerun once and those specimens that failed to show presence of human DNA or were incomplete pairs were excluded from analysis.
The Xpert® CT/NG assay (from here referred to as Xpert) is run on the GeneXpert® System and can be implemented in clinical settings without the need for central laboratory processing. That assay is run in approximately 90 minutes and results are displayed in tabular and graphic formats on a computer system. The GeneXpert® System has three main internal quality control mechanisms to ensure ideal test functioning and conditions.18 One of those internal quality control mechanisms is the sample adequacy control (SAC), which detects the presence of the gene encoding hydroxymethylbilane synthase (HMBS), a single-copy human cellular housekeeping gene, to monitor whether the sample contains human DNA. A negative SAC indicates that inadequate numbers of human cells were present in the sample, which can be due to sample degradation, insufficient mixing, or because of an inadequately collected specimen. The primers and probes in the Xpert CT/NG Assay detect chromosomal sequences in the CT and NG bacteria, with one target for CT and two different targets for NG. Both of the NG targets need to be positive for the Xpert CT/NG Assay to return a positive NG result. The testing methods occurred in accordance with the manufacturer directions. Xpert results were neither used for clinical management nor were communicated to the participants. Indeterminate Xpert test results were rerun once and those specimens that failed to show presence of human DNA or were incomplete pairs were excluded from analysis.
