Increasing yield of pharyngeal Chlamydia trachomatis among male gay and bisexual clinic attendees in Sydney: an observational study.

Unlabelled: Background The aim of the present study was to describe the temporal trends in Chlamydia trachomatis (CT) testing yield among gay and bisexual male (GBM) sexual health clinic attendees in Sydney.

Methods: All CT testing occasions among GBM from January 2011 to December 2014 were reviewed. Yield was defined as the proportion of testing occasions where CT was detected.

Results: In all, 2917 GBM were tested on 5445 occasions. CT was detected on 439 (8.1%; 95% confidence interval (CI) 7.4-8.8%) occasions. Pharyngeal, urethral and anorectal CT were detected on 74 (1.4%; 95% CI 1.1-1.7%), 109 (2.0%; 95% CI 1.7-2.4%) and 333 (6.1%; 95% CI 5.5-6.8%) occasions respectively. Over the study period, there was a significant increase in pharyngeal CT yield (from 0.70% to 1.6%; odds ratio (OR) 1.25; 95% CI 1.01-1.55; P=0.043), which remained borderline significant (OR 1.22; 95% CI 0.99-1.52; P=0.067) when adjusted for age. There was no change in yield of either urethral or anorectal infections. Almost half the pharyngeal CT (n=35; 47.3%) occurred without concurrent anogenital infection. Excluding those who would have received anti-chlamydial treatment for another reason, 27.0% of pharyngeal and 4.6% of all CT infections would not have been treated without pharyngeal testing.

Conclusions: A recent temporal increase was observed in the yield of pharyngeal CT without a concurrent increase in anogenital yield. Ongoing surveillance is warranted to inform testing guidelines for GBM.