Evaluation of the Performance of the Cobas CT/NG Test for Use on the Cobas 6800/8800 Systems for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in Male and Female Urogenital Samples

Abstract

The clinical performance of the Cobas CT/NG assay on the Cobas 6800/8800 systems (Cobas) for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae was established in a multisite, prospective collection study using male and female urogenital specimens; supportive data from archived specimens were also included. The results obtained with the Cobas assay were compared with the patient infected status derived from a combination of U.S. Food and Drug Administration-approved nucleic acid amplification tests to determine the sensitivity and specificity of detection from each sample type. The sensitivity of Cobas for the detection of C. trachomatis in female specimens was 95.6% (95% confidence interval [CI], 92.4% to 97.4%) for urine; 98.6% (95% CI, 95.2% to 99.6%) and 99.2% (95% CI, 95.4% to 99.9%) for clinician- and self-collected vaginal swab specimens, respectively; 93.3% (95% CI, 89.6% to 95.7%) for endocervical swabs; and 92.5% (95% CI, 88.7% to 95.1%) for cervical swab samples in PreservCyt. The specificity for the detection of C. trachomatis was ≥98.8% for all female sample types. Sensitivity and specificity estimates of Cobas for the detection of C. trachomatis in male urine samples were 100% (96.8% to 100.0%) and 99.7% (95% CI, 99.2% to 99.9%), respectively. The sensitivity of Cobas for the detection of N. gonorrhoeae in female specimens was 94.8% (95% CI, 89.6% to 97.4%) for urine; 100.0% (95% CI, 87.9% to 100.0%) and 100.0% (95% CI, 87.9% to 100.0%) for clinician- and self-collected vaginal swab specimens, respectively; 97.0% (95% CI, 91.5% to 99.0%) for endocervical swabs; and 96.6% (95% CI, 90.6% to 98.8%) for cervical samples in PreservCyt; the specificity for all female sample types was >99.0%. The sensitivity and specificity of Cobas for detecting N. gonorrhoeae in male urine were 100.0% (95% CI, 95.8% to 100.0%) and 99.5% (95% CI, 98.8% to 99.8%), respectively. Fully automated assays help fill the clinical need for a sensitive, high-throughput screening tool to aid public health efforts to control C. trachomatis and N. gonorrhoeae infections.

Keywords: Chlamydia trachomatis; Cobas CT/NG assay; Neisseria gonorrhoeae; PCR; genital infection; molecular diagnostics; nucleic acid amplification test; sexually transmitted infection.

FIG 1

Patient disposition and specimen evaluability in the prospective population. ^a, reasons for exclusion included clinician decision (n = 3), the patient did not meet the eligibility criteria (n = 21), the patient was unwilling to provide informed consent (n = 37), pregnancy (n = 1), protocol deviation (n = 14), screen failure (n = 1), and withdrawal by the patient (n = 15); ^b, nonevaluable subjects were those without an assigned C. trachomatis/N. gonorrhoeae patient infected status (PIS; n = 51) or invalid/failed Cobas test results (n = 1). ^c, patients were considered evaluable if they had both a designated C. trachomatis/N. gonorrhoeae PIS, based on the prespecified PIS algorithm, and valid Cobas results for at least one sample type; ^d, valid samples were those with valid Cobas results and were included in the analysis; samples with missing, invalid, or failed Cobas results were excluded from the analysis; ^e, prospectively enrolled women were randomly assigned to the clinician-collected (CC) or self-collected (SC) vaginal swab specimen group. CT, C. trachomatis; NG, N. gonorrhoeae.

FIG 2

Venn diagrams comparing C. trachomatis-positive results across NAATs with urine samples from women (A), vaginal swab samples (B), and urine samples from men (C).

FIG 3

Venn diagrams comparing N. gonorrhoeae-positive results across NAATs with urine samples from women (A), vaginal swab samples (B), and urine samples from men (C) (prospective population).