High burden of chlamydia and gonorrhoea in pharyngeal, rectal and urethral sites among Thai transgender women: implications for anatomical site selection for the screening of STI

Objective Comprehensive data on Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections to guide screening services among transgender women (TGW) are limited. We studied the burden of CT/NG infections in pharyngeal, rectal and urethral sites of Thai TGW and determined missed CT/NG diagnoses if selected site screening was performed. Methods Thai TGW were enrolled to the community-led test and treat cohort. CT/NG screening was performed from pharyngeal swab, rectal swab and urine using nucleic acid amplification test. CT/NG prevalence in each anatomical site was analysed, along with the relationships of CT/NG among the three anatomical sites. Results Of 764 TGW included in the analysis, 232 (30.4%) had CT/NG infections at any anatomical site, with an overall incidence of 23.7 per 100 person-years. The most common CT/NG infections by anatomical site were rectal CT (19.5%), rectal NG (9.6%) and pharyngeal NG (8.1%). Among 232 TGW with CT/NG infections at any anatomical site, 22%-94.4% of infections would have been missed if single anatomical site testing was conducted, depending on the selected site. Among 668 TGW who tested negative at pharyngeal site, 20.4% had either rectal or urethral infections. Among 583 TGW who tested negative at the rectal site, 8.7% had either pharyngeal or urethral infections. Among 751 TGW who tested negative at the urethral site, 19.2% had either pharyngeal or rectal infections. Conclusion Almost one-third of Thai TGW had CT/NG infections. All-site screening is highly recommended to identify these infections, but if not feasible rectal screening provides the highest yield of CT/NG diagnoses. Affordable molecular technologies and/or CT/NG screening in pooled samples from different anatomical sites are urgently needed.