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Clinical sciences poster session 1: and related syndromes
P3-S1.19 Evaluation of the cobas® 4800 CT/NG test using clinician and self-collected vaginal swabs, cervical specimens in PreservCyt solution, and pharyngeal throat wash specimens
  1. M Krevolin,
  2. A Sunhachawee,
  3. D Hardy,
  4. J Pane,
  5. E Cervantes,
  6. R Kotadia,
  7. S Joshi,
  8. R Puckett,
  9. O Liesenfeld
  1. Roche Molecular Systems, Pleasanton, USA

Abstract

Objective To evaluate the limit of detection (LOD), inclusivity, exclusivity, and interfering substances of the cobas® 4800 CT/NG Test using vaginal, PreservCyt, and pharyngeal specimens.

Methods Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) cultures were diluted into pools of negative patient specimens at six concentrations to determine the LOD (lowest concentration giving a ≥95% hit rate). A panel of 15 serovars of CT, plus the Swedish variant (nvCT), and 45 strains of NG was diluted into each sample matrix to determine inclusivity. To ensure specificity, a panel of 184 non-CT and non-NG organisms that may be found in the oral or urogenital region was tested at Ġ≥10^5 CFU or copies/ml. The organisms were diluted into CT/NG positive and negative samples. Ten CT/NG positive and negative samples were spiked with blood (up to 5%), leukocytes (up to 10^7 cells/ml), cervical mucus, and saliva at concentrations up to 10% to check for interference. Ten (for pharyngeal) and 18 (for urogenital) over-the-counter products were also tested.

Results LODs were as follows: Vaginal CT 10 IFU/ml, NG 100 CFU/ml; PreservCyt CT 0.6 IFU/ml, NG 3.5 CFU/ml, Pharyngeal CT 0.5 IFU/ml, NG 2.25 CFU/ml. All 15 serovars of CT, plus the Swedish variant (nvCT), and 45 strains of NG were detected at, or near the LOD. No cross reactivity was noted with 184 non-CT and non-NG organisms in any specimen type. Vaginal but not PreservCyt samples showed interference from leukocytes at >10^6 cells/ml. This interference was noted as clot detections and samples were not processed. Pharyngeal samples showed false negative results in the presence of blood at >0.25%, and saliva at >2.5%. No interference was noted with any over-the-counter products in any specimen type.

Conclusions Vaginal, PreservCyt, and pharyngeal specimens are suitable sample types for the cobas® 4800 CT/NG Test.

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