High Rates of Asymptomatic Gonorrhea (GC) and Chlamydia (CT) Infections in Men Who Have Sex with Men (MSM) Undergoing Anal Dysplasia Screening

Background: MSM referred by primary care clinicians for anal dysplasia screening are also tested for GC and CT at the oropharynx, anus and urethra. In December 2011 we switched to nucleic acid amplification testing (NAATs) from culture.  Urine testing was always DNA based.  We compared STI results obtained by culture vs. NAATs.

Methods: A retrospective analysis of MSM tested for GC and CT at ≥1 site from July-November 2011 (culture) and December 2011 – April 2012 (NAATs).

Results: Of 799 MSM (median age 42; range 17-81 years) tested by culture or NAATs at ≥1 site, 57.7% were HIV+, 23.4% were monogamous, 71.1% had receptive anal sex, 66% had insertive anal sex, 68% had oral sex with >1 partner, 70.7% had history of a prior STI and 12.1% had possible STI-related symptoms. Characteristics were not significantly different between the 384 MSM tested by culture and 415 tested by NAATs. Overall 3.4% and 15.1% of MSM tested positive for GC and/or CT by culture and NAATS, respectively (p<0.001).  GC was identified by culture vs NAATS in the oropharynx 0 vs. 3.9%, urethra 0.3% vs 0%, anus 0.5% vs 2.7%, respectively (oropharynx p<0.001, anal p=0.02). CT was identified by culture vs NAATS in the oropharynx 0 vs 3.4%, urethra 2.3% vs 1.4% and anus 0.5% vs 8.0%, respectively (p<0.001 for oropharynx and anus). With NAATs 81.5% of GC and 74% of CT infections identified were asymptomatic. In multivariable analysis, testing positive for GC and/or CT by NAATS was significantly associated with HIV+; adjusted odds ration (AOR) 3.5(95%CI 1. 8-7.0), younger age; AOR 0.95(95%CI 0.92-0.98) and being symptomatic; AOR 8.2(95%CI 4.0-17.2).

Conclusions:  MSM referred for anal dysplasia screening have high rates of STI’s unidentified by primary care clinicians. Most are asymptomatic.  NAATs is superior to culture and MSM should undergo 3 orifice testing.