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

Bristow, Claire C. PhD, MPH, MSc*; McGrath, Mark R. MPH; Cohen, Adam C. PhD, MPH; Anderson, Laura J. MPH; Gordon, Kristie K. BA†§; Klausner, Jeffrey D. MD, MPH‡§

Sexually Transmitted Diseases: July 2017 - Volume 44 - Issue 7 - p 398–400
doi: 10.1097/OLQ.0000000000000627

Abstract: 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.

Our study found high concordance between the Xpert CT/NG assay (Cepheid, Sunnyvale, CA) and Aptima Combo 2 (Hologic, Inc, San Diego, CA) for use with extragenital specimens.

From the *Division of Global Public Health, Department of Medicine, University of California San Diego, La Jolla, CA; †AIDS Healthcare Foundation, Los Angeles, CA; ‡UCLA Fielding School of Public Health, Los Angeles, CA; and §UCLA David Geffen School of Medicine, Los Angeles, CA

The authors thank Cepheid for the donation of test equipment and supplies and the study participants for their contributions toward this study. In addition, the authors thank Rosalba Castro, the laboratory technician at AIDS Healthcare Foundation, and Katheryn Salow, a research associate at AIDS Healthcare Foundation, for their valuable contributions toward the success of this study.

Author C.C. Bristow acknowledges funding from Fogarty International Center 5R25TW009343 FIC. Cepheid provided all testing materials.

Conflict of interest: None declared.

Correspondence: Claire C. Bristow, PhD, MPH, MSc, University of California San Diego, 9500 Gilman Dr, 0507, La Jolla, CA 92093-0507. E-mail:

Received for publication January 23, 2017, and accepted March 12, 2017.

© Copyright 2017 American Sexually Transmitted Diseases Association