Pharyngeal Chlamydia trachomatis Screening in Women: A Retrospective Study

Background: Chlamydia trachomatis (CT) infections are among the most prevalent sexually transmitted infections (STIs), particularly affecting young adults. In women, CT can cause pelvic inflammatory disease, infertility, and ectopic pregnancy, justifying routine vaginal swab screening. However, due to diverse sexual practices, CT can colonize multiple anatomical sites, including the pharynx. Pharyngeal CT carriage in women is underdiagnosed and may contribute to ongoing transmission. Objectives and Methods: This study aimed to assess the rate of pharyngeal CT carriage, describe the rate of isolated pharyngeal CT carriage, and identify factors with pharyngeal CT carriage. We conducted a retrospective study at Montpellier University Hospital (France) and the public STI clinic of the city, including all cisgender women who provided at least one pharyngeal sample for CT testing between May 1^st, 2018, and June 30, 2023. Results: A total of 567 women (median age 24 years) contributed 666 samples. Pharyngeal CT carriage was found in 2.8% of the population. Most cases were concurrent with vaginal CT, but 5 women had isolated pharyngeal carriage, representing 0.9% of the study population and accounting for 11.1% of detected cases. Young age and a history of CT infection appeared to be independently associated with pharyngeal CT carriage in multivariate mixed model analysis. Conclusion: We observed a pharyngeal CT carriage rate consistent with the literature, which was low but not insignificant. Notably, 11.1% of CT infections would have been missed without pharyngeal screening, underscoring the importance of considering extragenital testing.