ABSTRACT
Nucleic acid amplification testing (NAAT) is the preferred method to detect
Chlamydia trachomatis
and
Neisseria gonorrhoeae
, but no commercial tests are cleared by the U.S. Food and Drug Administration for use with extragenital swab samples. This study evaluated the performance of the Gen-Probe Aptima Combo2 assay (Aptima) and the Cepheid Xpert CT/NG assay (Xpert) to detect
C. trachomatis
and
N. gonorrhoeae
in rectal and pharyngeal samples from 224 men and 175 women reporting a history of anal receptive sexual intercourse. Discordant results between the NAATs were repeated using the assays APTIMA CT or APTIMA GC, which target alternate primers, as the confirmatory tests.
C. trachomatis
was detected from 59 rectal swabs and 8 pharyngeal samples, with 97.7% and 99.5% agreement between the two test systems, respectively. For
C. trachomatis
, Xpert was 95% sensitive (95% CI, 86 to 99%) and Aptima was 92% sensitive (95% CI, 81 to 97%) from rectal swabs, while both systems were 100% sensitive from pharyngeal samples.
N. gonorrhoeae
was detected from 30 rectal and 40 pharyngeal samples, with 99.5% and 97.5% agreement between the two test systems. The sensitivity of Xpert for
N. gonorrhoeae
from rectal swabs was 100% (95% CI, 88 to 100%) versus 93% (95% CI, 78 to 99%) for Aptima. From pharyngeal swab samples, Xpert was 98% sensitive (95% CI, 87 to 99.9%) versus 93% (95% CI, 80 to 98%) for Aptima. For
C. trachomatis
, neither system was >95% sensitive from the rectum, though both were >99.5% specific. For
N. gonorrhoeae
, Xpert had higher sensitivity than Aptima, but with more false positives from pharyngeal samples.
Use of Nucleic Acid Amplification Testing for Diagnosis of Anorectal Sexually Transmitted Infections