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Sex Transm Infect 92:155-160 doi:10.1136/sextrans-2015-052214
  • Epidemiology
  • Original article

An estimate of the proportion of symptomatic gonococcal, chlamydial and non-gonococcal non-chlamydial urethritis attributable to oral sex among men who have sex with men: a case–control study

Editor's Choice
  1. Matthew R Golden1,2,3
  1. 1Department of Medicine, Division of Allergy and Infectious Diseases, University of Washington, Seattle, Washington, USA
  2. 2Public Health, Seattle & King County HIV/STD Program
  3. 3Department of Epidemiology, University of Washington, Seattle, Washington, USA
  4. 4Department of Global Health, University of Washington, Seattle, Washington, USA
  1. Correspondence to Dr Lindley A Barbee, Department of Medicine, Division of Allergy and Infectious Disease, University of Washington, 325 9th Ave, Box 359777, Seattle, WA 98104, USA; lbarbee{at}u.washington.edu
  • Received 15 June 2015
  • Revised 29 July 2015
  • Accepted 4 August 2015
  • Published Online First 21 August 2015

Abstract

Background Sexually transmitted infections (STIs) of the pharynx are common among men who have sex with men (MSM); the degree to which these infections are transmitted through oral sex is unknown.

Methods We conducted a case–control study of MSM attending Public Health—Seattle & King County STD Clinic between 2001 and 2013 to estimate the proportion of symptomatic urethritis cases attributable to oral sex using two methods. First, we categorised men into the following mutually exclusive behavioural categories based on their self-reported sexual history in the previous 60 days: (1) only received oral sex (IOS); (2) 100% condom usage with insertive anal sex plus oral sex (PIAI); (3) inconsistent condom usage with anal sex (UIAI); and (4) no sex. We then determined the proportion of cases in which men reported the oropharynx as their only urethral exposure (IOS and PIAI). Second, we calculated the population attributable risk per cent (PAR%) associated with oral sex using Mantel–Haenszel OR estimates.

Results Based on our behavioural categorisation method, men reported the oropharynx as their only urethral exposure in the past 60 days in 27.5% of gonococcal urethritis, 31.4% of chlamydial urethritis and 35.9% non-gonococcal, non-chlamydial urethritis (NGNCU) cases. The PAR%s for symptomatic gonococcal urethritis, chlamydial urethritis and NGNCU attributed to oropharyngeal exposure were 33.8%, 2.7% and 27.1%, respectively.

Conclusions The pharynx is an important source of gonococcal transmission, and may be important in the transmission of chlamydia and other, unidentified pathogens that cause urethritis. Efforts to increase pharyngeal gonorrhoea screening among MSM could diminish STI transmission.