C-153. Evaluation of Gen-Probe Combo 2 Performed on Tigris DTS System for Detecting Chlamydia trachomatis and Neisseria gonorrhoeae

J. Aslanzadeh, J. Miller, Y. Baldonada, P. Hamilton, I. Ratkiewicz;
Hartford Hosp., Hartford, CT.

The APTIMA Combo 2® assay performed on fully automated Tigris DTS system is a target amplification test that utilizes target capture for the in vitro qualitative detection and differentiation of rRNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (GC) in vaginal, endocervical and male urethral swab as well as urine and Cytec ThinPrep specimens. We evaluated the performance of this assay in two separate studies. In a blind study, we tested 124 samples previously tested for CT/GC in another laboratory. Over all, 87 specimens were negative for both organisms, 24 samples were positive for CT, 11samples were positive for GC and 1 sample was positive for CT and GC at both laboratories. One specimen positive for CT at the reference laboratory was repeatedly negative at our laboratory and was considered a false negative. The overall sensitivity specificity and positive and negative predictive value of the Tigris for CT was (96%, 100%, 100% 99%) and GC was (100%, 100%, 100%. 100%) respectively. In a subsequent prospective study, we compared the Tigris to the BD ProbeTec Viper system using 555 endocervical samples collected with the BD ProbeTec swab. Swabs were placed in BD extraction vials and 1 ml aliquot from each vial was transferred into Tigris tubes before denaturation and was tested simultaneously on both instruments. Five hundred thirty five (535) samples were negative for CT/GC, 11 samples were positive for CT and 7 samples were positive for GC on both instruments. Four (4) samples repeatedly positive for CT on Tigris were initially negative for CT on Viper but on repeat testing, 2 out of 4 samples were positive for CT on Viper. The remaining 2 specimens were negative on repeat testing. In addition, in a 9 months study where positive results for CT and GC were repeated in duplicate on both instruments, BD ProbeTec failed to repeat positive GC and CT 16% and 8.2 % of the time respectively. In contrast, Tigris failed to repeat positive GC and CT 2% and 2.3% of the time respectively. We conclude that APTIMA Combo 2® assay performed on Tigris DTS is highly senstive and specific for detecting CT/GC in clinical samples.