Study backs guidance on screening for pharyngeal chlamydia
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Compared with other extragenital STIs, the incidence and duration of pharyngeal chlamydia are low among men who have sex with men, according to a recent study.
Researchers said the findings support national guidelines that recommend against routine screening for pharyngeal chlamydia.
“Our results intimate that pharyngeal [Chlamydia trachomatis (CT)] infection is not likely to be a major driver in CT transmission at the population level, but the full extent of pharyngeal CT’s role in transmission remains unclear,” they wrote in Clinical Infectious Diseases.
“This was part of a larger study to examine the incidence and duration of pharyngeal and rectal gonorrhea and chlamydia,” Christine M. Khosropour, PhD, MPH, an epidemiologist and assistant professor of epidemiology at the University of Washington, told Healio.
“These infections seem to be commonly diagnosed, but we know surprisingly little about how often people acquire these infections or how long they last,” Khosropour said. “Pharyngeal chlamydia is the least common extragenital STI, but it may play a role in population-level chlamydia transmission.”
For the study, Khosropour and colleagues enrolled men who have sex with men (MSM) in a 48-week natural history cohort study in Seattle between March 2016 and December 2018. They tested participants’ self-collected pharyngeal specimens weekly using nucleic acid amplification testing.
Throughout the study period, 140 participants contributed 70.5 person-years (PY) of follow-up, with two participants having pharyngeal chlamydia at enrollment. According to the study, primary analyses revealed eight pharyngeal chlamydia cases among six MSM for an incidence of 11.4 per 100 PY (95% CI, 6-21.9), whereas a sensitivity analysis showed that there were 19 cases among 16 MSM, yielding an incidence of 27.1 per 100 PY (95% CI, 18.5-39.8).
Overall, the researchers determined that the median duration of pharyngeal chlamydia was 6 weeks (95% CI, 2 weeks-undefined) in primary analyses and 2 weeks (95% CI, 1.1-6) in a sensitivity analysis. They reported that the duration was shorter for those with a history of chlamydia compared with those without (3.6 weeks vs. 8.7 weeks; P = .02).
“Given the relatively short duration of infection and the fact that most infections were asymptomatic, our findings support CDC’s guidelines that do not recommend routine screening for pharyngeal chlamydia. However, it is also important to note that we still do not know the full extent of pharyngeal chlamydia’s role in population-level transmission of chlamydia,” Khospropour said. “Based on available data, routine screening for pharyngeal chlamydia does not need to be implemented, but we still need to understand its role in population-level chlamydia transmission.”
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