LAUSR

Background Universal anorectal testing for Chlamydia trachomatis (chlamydia) among women is not recommended in many countries, while anorectal chlamydia infections are common. Missed anorectal infections might cause sequelae at the genital site if autoinoculation from the anorectum is possible, but evidence is limited. This study investigates the association between potentially missed anorectal infections and subsequent genital chlamydia infections in women, using not being tested at the anorectal site as a proxy for having a potentially missed anorectal infection. Methods We included all women with a repeat chlamydia test within 1 year (with at least a genital test) from the Dutch sexual health centre surveillance between 2014 and 2019. Multilevel logistic regression analyses were used to identify determinants of genital chlamydia infection at the repeat test, with anorectal testing at the previous chlamydia test as the main determinant. Results A total of 40 217 women were included in the analyses, of whom 15.4% tested chlamydia-positive genitally at their second test. Not being tested anorectally at the first test was an independent risk factor for genital chlamydia infection at the repeat test (adjusted OR 1.24, 95% CI 1.15 to 1.33). This association was in the same range as most other significant risk factors in the model: low education level, no condom use, STI symptoms and previous STI diagnosis. Young age (<20 years) (2.67, 2.39–2.98) and those who received partner notification (3.11, 2.91–3.31) showed stronger associations. The findings were robust; correcting for interactions and a sensitivity analysis stratifying by chlamydia infection at first visit did not show significant differences in the adjusted OR of not being tested anorectally at first test. Conclusion The results are suggestive of an autoinoculation process from the anorectal to the genital anatomical site in women. To enhance chlamydia control, future studies on the role of extragenital testing and autoinoculation in chlamydia transmission are needed.