The performance of pooled three anatomic site testing for Chlamydia trachomatis and Neisseria gonorrhoeae among men who have sex with men and transgender women.

Bristow, Claire C; Mehta, Sanjay R; Hoenigl, Martin; Little, Susan J

BACKGROUND While molecular testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) is highly sensitive than traditional approaches, the cost can be prohibitive. Those high costs are amplified when the recommended screening approach is used, which requires separate testing of specimens from three anatomic sites (rectal, pharyngeal and urogenital). While individual molecular testing is standard of care (SOC), pooled testing may offer a cost-saving alternative. METHODS Using the Xpert® CT/NG assay (Cepheid, Sunnyvale, CA) we tested urine, rectal and pharyngeal swabs for CT and NG in a high-risk cohort of participants assigned male at birth who reported sex with other persons who were assigned male at birth. Remnant specimens (0.34 mL from each anatomic site) were combined to perform a single 'pooled' test. We calculated positive and negative percent agreement between the pooled testing results with SOC Xpert CT/NG test results as the reference. RESULTS We conducted 644 pooled tests. Of those, 598 (92.3%) gave CT and NG results. The CT positive and negative percent agreement were 90.1% (95% CI: 80.7%, 95.9%) and 99.2% (98.1%, 99.8%), respectively. The NG positive and negative percent agreement were 96.2% (95% CI: 86.8%, 99.5%) and 99.8% (95% CI: 99.0%, 100%), respectively. Pooled testing identified 4 CT and 1 NG infections that were negative at all anatomic sites by individual testing. CONCLUSIONS Three-site pooled CT and NG testing performs similarly to single anatomic site testing among tests providing a valid result. Future cost analyses should evaluate the cost effectiveness of pooled three-site testing to determine if such a strategy improves the feasibility and accessibility of molecular STI testing.