Performance of the Abbott RealTime CT/NG for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae

A multicenter clinical study was conducted to evaluate the performance characteristics of the Abbott RealTime CT/NG assay, a multiplex real-time PCR assay, for simultaneous detection of Chlamydia trachomatis and Neisseria gonorrhoeae. The specimens were collected from a total of 3,832 male and female subjects at 16 geographically diverse sites. Specimens included male and female urine samples, male urethral swabs, female endocervical swabs, and self-collected and clinician-collected vaginal swabs. Specimens were tested with the automated Abbott RealTime CT/NG assay, Aptima Combo 2 assay (Gen-Probe), ProbeTec ET CT/GC assay (Becton Dickinson), and culture for N. gonorrhoeae. The Aptima Combo 2 assay, the ProbeTec assay, and the N. gonorrhoeae culture were used as the reference assays. For each subject, a patient infected status (PIS) was determined based on the combined results from the reference assays. The overall prevalence in female subjects was 8.9% for C. trachomatis and 3.8% for N. gonorrhoeae. The overall male prevalence was 18.2% for C. trachomatis and 16.7% for N. gonorrhoeae. The overall sensitivity and specificity of the Abbott RealTime CT/NG assay were 92.4% and 99.2% for C. trachomatis and 96.9% and 99.7% for N. gonorrhoeae, respectively. In comparison, the sensitivity and specificity, respectively, for the Aptima Combo 2 assay were 94.5% and 99.0% for C. trachomatis and 96.1% and 99.5% for N. gonorrhoeae, and those for the ProbeTec ET assay were 90.3% and 99.5% for C. trachomatis and 92.0% and 97.3% for N. gonorrhoeae in this study. The Abbott RealTime CT/NG assay offers C. trachomatis and N. gonorrhoeae dual detection with high sensitivity and specificity. The automated assay provides a useful alternative nucleic acid amplification assay for clinical laboratories and clinicians.Chlamydia trachomatis and Neisseria gonorrhoeae are the two most prevalent bacterial sexually transmitted infections (STIs) reported to the Centers for Disease Control and Prevention (CDC) (2). Together these two infections accounted for over 1.5 million cases of STIs in 2008. The CDC estimates that sexually transmitted diseases (STDs) cost the health care system $1.5 billion annually. Since these infections, especially chlamydia, are most often asymptomatic, the CDC recommends yearly screening for chlamydia in all sexually active women ages 16 to 25 years. Since coinfections are common, many diagnostic test platforms assay for both organisms. Although there are several commercial assays available for performing nucleic acid amplification tests (NAATs), which are now recommended by the CDC as the test of choice, new assays and new platforms are needed by both private and public health programs.The Abbott RealTime CT/NG assay is a new real-time PCR assay for the direct, qualitative detection of the plasmid DNA of Chlamydia trachomatis and the genomic DNA of Neisseria gonorrhoeae in female endocervical or vaginal swab specimens, in male urethral swab specimens, and in male and female urine specimens from symptomatic and asymptomatic individuals. There were several sets of objectives of this study: (i) to determine the performance characteristics of the Abbott RealTime CT/NG assay compared to those of other amplified assays using specimens obtained from symptomatic and asymptomatic male and female subjects from clinical sites with high or low prevalence of Chlamydia trachomatis and/or Neisseria gonorrhoeae; (ii) to demonstrate the precision of the Abbott RealTime CT/NG assay using a precision panel consisting of combinations of high and low concentrations of Chlamydia trachomatis and Neisseria gonorrhoeae specimens; (iii) to evaluate the clinical sensitivity, clinical specificity, positive predictive value (PPV), and negative predictive value (NPV) of the Abbott RealTime CT/NG assay in symptomatic and asymptomatic individuals from high- and low-prevalence sites; (iv) to compare the performance of the new Abbott assay with that of the Gen-Probe Aptima Combo 2 assay for female endocervical and vaginal swabs, male urethral swabs, and male and female urine specimens; (v) to compare the performance of the Abbott assay with those of the Becton Dickinson ProbeTec ET Chlamydia trachomatis and Neisseria gonorrhoeae amplified DNA assays (ProbeTec ET) for female endocervical swabs and male and female urine specimens; and (vi) to evaluate the procedure for self-collection of a vaginal swab specimen using the Abbott multi-Collect specimen collection kit.