Rectal Chlamydia testing among MSM attending an STD clinic

CDC recommends testing Men who have Sex with Men (MSM) at all exposure sites. A study at City Clinic in San Francisco found high prevalence of Chlamydia (CT) and Gonorrhea (GC) rectal infections among MSM using a nucleic acid amplification test (NAAT). Following internal validation by our Public Health Lab a protocol for testing at all exposure sites using APTIMA combo 2 was implemented in Philadelphia Department of Public Health STD clinics.

Prior to implementing NAAT testing at rectal site for GC/CT, rectal cultures were routinely performed for GC but no testing for Chlamydia was available. We sought to determine the prevalence of rectal Chlamydia trachomatis infections among MSM and the number of patients who would not have received treatment under the previous testing protocol.

Data were extracted from our medical record system to include MSM who had a rectal NAAT ordered. Other test results completed on other exposure sites were included.

Preliminary results from the first months of implementation show that 177 MSM patients were seen, 74 (41.8%) were tested for rectal Chlamydia. Fourteen (18.9%) positive rectal Chlamydia tests were diagnosed. Seven of the 14 would have received empirical treatment for Chlamydia based on a positive rectal NAAT result for gonorrhea (N=6) or a diagnosis of NGU (N=1).

Without NAAT rectal testing, our STD clinic would have missed treating 7cases of Chlamydia among MSM. This analysis provides further supporting evidence that NAAT testing needs to be routine for higher risk populations.