Impact of Chlamydia trachomatis Serovars on the Analytical Sensitivity of the GEN-PROBE® APTIMA Combo 2® Assay and New BD ProbeTec™ CTQx and GCQx Amplified DNA Assays*

Wednesday, March 12, 2008
Continental Ballroom
Christine Welborn, MS , Molecular, Becton Dickinson, Sparks, MD
Tom L. Brink, MS , Molecular, Becton Dickinson, Sparks, MD
Amy Lloyd , Molecular, Becton Dickinson, Sparks, MD
Daryl Shank , Molecular, Becton Dickinson, Sparks, MD
William Lebar , Hospital Consolidated Laboratories - Providence Hospital, Southfield, MI

BD has developed two novel assays for detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) for use with the BD Viper™ System. Walk-away automation is achieved through the extraction of DNA from clinical specimens by binding to ferric oxide, followed by amplification and real-time fluorescent detection.

To compare the analytical sensitivity of the BD ProbeTec™ Qx and GEN-PROBE® APTIMA Combo 2® (AC2) assays using samples containing known concentrations of CT and GC and to investigate the impact on performance of two different CT serovars.

APTIMA® Swab Transport Medium and Qx Swab Diluent were co-spiked with CT and GC as follows: 15 Elementary Bodies and 25 cells/mL; 7.5 EB and 12 cells/mL. Separate panels were prepared using CT serovars LGV2 and H. Negative controls consisted of uninoculated medium. Panels were tested according to the manufacturers' instructions.

For both platforms all CT/GC-negative samples yielded negative results.
BD ProbeTec™ CTQx and GCQx Amplified DNA Assays
Positive Percent Agreement (PPA) with expected results for CT and GC was 100% for each organism and with both CT serovars.
AC2 Assay
PPA for GC was 100% in the presence of both CT serovars. In contrast, PPA for CT-LGV2 was 100% whereas PPA for serovar H at the same levels was 0%. Repeat testing of the serovar H panel with the alternative APTIMA® CT Assay yielded 100% PPA.

In contrast with the BD ProbeTec™ Qx Assays and BD Viper™ System, the detection of CT by the GEN-PROBE® AC2 Assay was shown to be serovar dependent.

Under the conditions tested, the BD ProbeTec™ CTQx Assay was more analytically sensitive than the GEN-PROBE® AC2 Assay for detection of CT serovar H. Further experiments are required to determine impact on clinical performance.
*BD ProbeTec™ Qx Assays under development, not for sale or use
See more of: Poster Session 2
See more of: Oral and Poster