Multicenter prospective cohort study in Chlamydia trachomatis positive women after regular treatment to understand the transmission of anorectal CT infections.

Rationale:

Current national and international strategies for the control of Chlamydia trachomatis (CT) critically fail to obtain a reduction in transmission. In women, anorectal infections are about as common as genital CT. Yet anorectal CT remain untested as sexually transmitted infection (STI) clinics, general practitioners, hospital and population testing initiatives largely focus on genital CT. Part of untested anorectal CT is incidentally treated with the treatments applied for genital CT, as in women anorectal CT is often concurrent with genital CT. Yet, it is unknown whether transmission of anorectal CT can still occur after currently recommended treatment. Anorectal and genital CT were observed quite often after regular treatment (up to 40% detection by nucleic acid amplification tests-NAAT). Proposed reasons for such detection include a new (re-)infection from a partner or self-infection from another anatomic, e.g. anorectal, site. Anorectal infections are a potential reservoir for ongoing transmission of genital and anorectal CT in the population, between partners and between anatomic sites of an individual. Yet, neither the transmission potential nor the transmission impact of anorectal infections has been reported. The scientific evidence for the optimal control strategy for anorectal CT and thereby CT in its totality, is lacking.

Objective:

To understand the transmission of anorectal CT infections in women, i.e. from their male sexual partner(s) and from and to the genital region of the same woman, in women who receive routine care, in order to inform guidelines to optimize CT control.

Study population:

Participants are recruited from 3 large Dutch STI clinics, in South Limburg, Amsterdam and Rotterdam. Eligible participants are likely to reflect the STI clinic population, in terms of age, ethnicity and level of education. Participants include genital and/or anorectal CT positive women (n=400).

Study design:

A multicentre prospective cohort study is set up with biological and behavioural measurements after routine treatment of CT. During 3 months, the participants will be studied using a self-administered anorectal and vaginal swab that is self-collected pre-treatment (T0), and at the end of weeks 1, 2, 4, 6, 8, 10, and 12. Samples are tested using NAAT for presence of CT-DNA (detection), concentration (load), viability (weeks 4,8, and 12), and CT type (multilocus sequence typing-MLST) to confirm re-infection. To validate sexual exposure, chromosomal Y DNA (as a marker for semen exposure) in genital and anorectal samples is applied. At each sampling time, online self-administered questionnaires on behaviour (e.g. anorectal exposure) and symptoms will be completed.

Outcomes:

The outcome is detection of anorectal and genital CT at any of the time -points.

Primary outcome is incident detection by NAAT, and secondary outcomes include detection of viable CT and CT-DNA concentration.

Statistical analyses:

In statistical analyses, using logistic regression models, the impact of two key factors will be assessed (i.e. sexual exposure and alternate anatomic site of infection) on detection of anorectal and genital CT. In sub-analyses, the role of treatment-type is evaluated.

Expected results:

This project will provide scientific insight in the role of anorectal CT in maintaining the CT burden, and it will provide practical recommendations (STI guidelines) to reduce avoidable transmission. Implications will be to improve care strategies for (re-)testing and partner management that currently largely neglect anorectal CT, benefitting the individual (better fitting care) and public health (reducing burden) and eventually cost-effectiveness of care.

Inclusion Criteria:

• Chlamydia trachomatis test positive (genital and or anorectal)

Exclusion Criteria:

• (reported) co-infection with gonorrhoea
• (reported) co-infection with HIV
• (reported) co-infection with syphilis
• (reported) pregnant
• (reported) anti-Chlamydial antibiotic use (period screening-treatment)

Participants are recruited from 3 large Dutch STI clinics, in South Limburg, Amsterdam and Rotterdam. Eligible participants are likely to reflect the STI clinic population, in terms of age, ethnicity and level of education. Participants include genital and/or anorectal CT positive women (n=400).

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