Background: The etiology of NGU may differ in MSW and MSM. We evaluated whether exposures associated with NGU in MSW differ from those associated with NGU in MSM.
Methods: Between 12/16/2014-12/18/2015, we enrolled 120 men ≥16 years attending the Seattle STD Clinic into a stratified case-control study (30 NGU+ MSM, 30 NGU- MSM, 30 NGU+ MSW, 30 NGU- MSW). Men underwent a clinic exam, specimen collection, and computerized self-interview. NGU was defined as symptoms or visible discharge and ≥ 5 PMNs/HPF. Urine was tested for Chlamydia trachomatis (CT) and Mycoplasma genitalium(MG) using TMA (Hologic, Inc). We used multi-variable logistic regression to identify exposures independently associated with NGU.
Results: The mean age was 35.5 (SD±10.6); 67.9% of men were White and 16.1% were Black; 25.2% of men reported current smoking. CT and MG were detected in 8 (26.7%) and 3 (10.0%) MSW with NGU, respectively, but neither was detected in MSW without NGU. Among MSM, CT and MG were detected in 11 (36.7%) and 6 (20%) men with NGU, respectively, and each was detected in 1 (3.3%) man without NGU. MSM who reported current smoking had lower odds (AOR=0.10; 95%CI=0.02-0.64) and MSM who reported insertive anal sex at last sex (AOR=7.93; 95%CI=2.16-29.09) or receipt of oral sex at last sex (AOR=2.96; 95%CI=0.76-11.44) had greater odds of NGU than MSM who did not. MSW who had ever had an anonymous partner (AOR=5.20; 95%CI=1.16-23.35) and Black MSW (AOR=4.41; 1.10-17.64) had greater odds of NGU than MSW who had not. No other exposures were significantly associated with NGU in either group.
Conclusions: Insertive anal sex among MSM may be an important exposure for NGU, potentially related to acquisition of rectal bacteria. Ever having had an anonymous partner may be an important risk factor in MSW, but may also be a marker for unmeasured exposures.