Nucleic acid amplification tests in the diagnosis of chlamydial and gonococcal infections of the oropharynx and rectum in men who have sex with men

Background: Several nucleic acid amplification tests (NAATs) are US Food and Drug Administration-cleared for detecting urogenital Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) infection, but they have not been adequately evaluated for the relatively common oropharyngeal or rectal CT and GC infections in men, who have sex with men (MSM). Methods: Multiple swabs were collected from the oropharynx and rectum of MSM attending a city sexually transmitted disease clinic. The specimens were tested by standard culture and the following NAATs: Roche's Amplicor (PCR), Becton Dickinson's ProbeTec (SDA), and Gen-Probe's APTIMA Combo 2 (AC2) for the detection of CT and GC. Confirmatory testing of specimens with discrepant results was done by NAATs using alternate primers. Results: A total of 1110 MSM were enrolled. Based on initial findings on 205 MSM, PCR had a 78.9% GC specificity with oropharyngeal swabs. Thus, we discontinued PCR testing for the rest of the study. For oropharyngeal GC (89 infections detected), sensitivities were 41% for culture, 72% for SDA, and 84% for AC2. For rectal GC (88 infections detected), sensitivities were 43% for culture, 78% for SDA and 93% for AC2. For oropharyngeal CT (9 infections detected), sensitivities were 44% for culture, 67% for SDA, and 100% for AC2. For rectal CT (68 infections detected), sensitivities were 27% for culture, 63% for SDA, and 93% for AC2. Specificities of SDA and AC2 were >= 99.4% for both organisms and anatomical sites. Conclusions: AC2 and SDA were far superior to culture for the detection of CT or GC from the oropharynx and rectum with AC2 detecting twice as many infections as culture. Further analyses with larger pharyngeal samples are needed, but clearly NAATs can improve our ability to diagnose rectal and oropharyngeal infection with CT or GC in MSM.