Reliable Rapid Assay for Gonorrhea and Chlamydia in the Emergency Department

Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are common sexually transmitted infections seen in the emergency department (ED). Due to an inability to reliably make accurate diagnosis by physical examination, concern for unreliable follow-up, and current delays in diagnostic nucleic acid amplification testing (NAAT), presumptive treatment active against CT and NG, as described by Centers for Disease Control clinical practice guidelines, is often performed.

The purpose of this study was to determine whether a rapid, urine NAAT performed in the ED is noninferior in its diagnostic sensitivity compared with a traditional, swab NAAT assay.

We performed a prospective, noninferiority study comparing two U.S. Food and Drug Administration-approved NAAT assays for CT and NG: a 90-min rapid assay, the Xpert CT/NG Assay (Cepheid, Sunnyvale, CA) using a urine sample vs. a traditional assay, the Aptima Combo 2 Assay (Gen-Probe Incorporated, San Diego, CA) using a swab sample. This study was registered on Clinicaltrials.gov (NCT02386514).

A total of 1162 patient samples were included in the primary analysis. We observed excellent kappa agreement between assays: NG for men, 1.00 (95% confidence interval [CI] 1.00-1.00); NG for women, 0.87 (95% CI 0.79-0.94); CT for men, 0.81 (95% CI 0.59-1.00); and CT for women: 0.85 (95% CI 0.80-0.90), as well as excellent negative and positive predictive values for the rapid assay.

Although the rapid Xpert CT/NG assay's diagnostic sensitivity did not meet our prespecified threshold for noninferiority, the diagnostic characteristics are robust enough to fit into a management pathway that may reduce unnecessary antibiotic use. There may be an opportunity to utilize the rapid Xpert CT/NG assay to improve accuracy of treatment in the ED.