Comparative Evaluation of 2 Nucleic Acid Amplification Tests for the Detection of Chlamydia trachomatis and Neisseria gonorrhoeae at Extragenital Sites

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Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections are frequently asymptomatic, requiring highly accurate diagnostic tests and proper management to prevent further transmission. We compared two nucleic acid tests, Xpert® CT/NG (Cepheid, Sunnyvale, CA) point-of-care platform and at an offsite clinical laboratory with Aptima Combo 2® (Hologic, Inc., San Diego, CA) assay, for the detection of extragenital infection in patients at an STI clinic in Hollywood, CA.

We calculated concordance between the two assays and used the exact binomial method to calculate 95% confidence intervals (CIs) for each specimen type and pathogen.

The concordance between the two assays was 97.7% (95% CI: 95.7%,99.0%) for 393 paired CT rectal results, 98.2% (95% CI: 96.4%,99.3%) for 391 paired NG rectal results and 98.4% (95% CI: 96.8%,99.4%) for 448 paired NG pharyngeal results.

The performance of Xpert® CT/NG assay in point-of-care testing in extragenital specimens was highly similar to the laboratory-based platform.

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