United States guidelines recommend azithromycin or doxycycline for chlamydia (Chlamydia trachomatis [CT]) treatment. These therapies are similarly efficacious for urogenital infections when outcomes are measured 7 to 42 days after treatment, although doxycycline may be superior for rectal infections. Some investigators have suggested that persistent rectal infections may lead to autoinfection of the urogenital tract, potentially resulting in higher rates of recurrent infection in azithromycin-treated women.
We used Washington State surveillance data to identify women 14 years or older with urogenital CT (1992–2015) treated with azithromycin or doxycycline. We defined persistent/recurrent CT as a repeat positive CT test result 14 to 180 days after treatment of the initial infection. We used log binomial regression to estimate the adjusted relative risk (aRR) of persistent/recurrent infection associated with treatment with azithromycin versus doxycycline.
From 1992 to 2015, there were 268,596 reported cases of urogenital CT, including 168,301 (63%) who received azithromycin and 66,432 (25%) who received doxycycline. The risk of persistent/recurrent urogenital CT was 6.7% and 4.7% in azithromycin- and doxycycline-treated cases, respectively (P < 0.001). Adjusting for age, race/ethnicity, year, pregnancy status, jurisdiction reporting, reason for examination, and gonorrhea coinfection, azithromycin-treated women were significantly more likely to have persistent/recurrent urogenital CT than doxycycline-treated women (aRR, 1.24; 95% confidence interval [CI], 1.19–1.30). Adjusting the retesting window to 21 to 180 days (aRR, 1.24; 95% CI, 1.19–1.30) and 28 to 180 days (aRR, 1.25; 95% CI, 1.19–1.30) did not alter our primary findings.
Persistent/recurrent urogenital CT may be more common among women treated with azithromycin than with doxycycline. The reason for this difference is uncertain and is an important area of future investigation.
Among 234,733 women with urogenital chlamydia in Washington State (1992–2015), persistent/recurrent urogenital Chlamydia trachomatis was more common among women treated with azithromycin compared with doxycycline (6.7% vs. 4.7%; P < 0.001).
From the *Department of Epidemiology, University of Washington, Seattle; †Washington State Department of Health, Olympia; Departments of ‡Biostatistics, §Global Health, and ¶Medicine, University of Washington; and ∥Public Health—Seattle and King County HIV/STD Program, Seattle, WA
Acknowledgments: The authors thank Tom Jaenicke at the Washington State Department of Health for his support of this project and Julie Dombrowski at the University of Washington for her guidance on the analysis.
This work was supported by the National Institutes of Health (Grant U19 AI113173 to C.M.K.).
Conflict of Interests: C.M.K., M.R.G., and L.E.M. have received donations of specimen collection kits and reagents from Hologic, Inc. M.R.G. has received research support from GSK. All other authors declare that they have no conflict of interest.
Correspondence: Christine M. Khosropour, PhD, MPH, Department of Epidemiology, Harborview Medical Center, Box 359777, 325 Ninth Ave, Seattle, WA 98104. E-mail: firstname.lastname@example.org.
Received for publication September 28, 2017, and accepted November 11, 2017.