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Frequency and risk factors for incident and redetected Chlamydia trachomatis infection in sexually active, young, multi-ethnic women: a community based cohort study

Research output: Contribution to journalArticlepeer-review

Adamma Aghaizu, Fiona Reid, Sally Kerry, Phillip E Hay, Harry Mallinson, Jorgen S Jensen, Sarah Kerry, Sheila Kerry, Pippa Oakeshott

Original languageEnglish
Pages (from-to)524-8
Number of pages5
Issue number7
Early online date6 Aug 2014
Accepted/In press5 Jul 2014
E-pub ahead of print6 Aug 2014
PublishedNov 2014


King's Authors


OBJECTIVE: To investigate the frequency and risk factors for incident and redetected Chlamydia trachomatis infection in sexually active, young, multi-ethnic women in the community.

DESIGN: Cohort study.

SETTING: 20 London universities and Further Education colleges.

PARTICIPANTS: 954 sexually experienced women, mean age 21.5 years (range 16-27), 26% from ethnic minorities, who were recruited to the Prevention of Pelvic Infection (POPI) chlamydia screening trial between 2004 and 2006, and returned repeat postal self-taken vaginal swabs 11-32 (median 16) months after recruitment.

RESULTS: The estimated annual incidence of chlamydia infection among 907 women who tested negative at baseline was 3.4 per 100 person-years (95% CI 2.5 to 4.6 per 100 person-years), but 6.6 per 100 person-years (95% CI 4.5 to 9.3 per 100 person-years) in the 326 teenagers (<20 years). Predictors of incident chlamydia infection were age <20 years (relative risk (RR) 4.0, 95% CI 2.1 to 7.5), and (after adjusting for age) a new sexual partner during 12 months follow-up (RR 4.4, 95% CI 2.0 to 9.9), smoking (RR 2.2 95% CI 1.2 to 3.9), concurrent bacterial vaginosis (RR 2.0 95% CI 1.1 to 3.9) and high risk carcinogenic human papillomavirus (RR 2.2, 95% CI 1.1 to 4.3). Of 47 women positive for chlamydia at baseline, 12 (25.5%, 95% CI 13.9% to 40.3%) had redetected infection at a median of 16 months follow-up. Taking into account follow-up time (65 person-years), the annual redetection rate was 18.5 per 100 person-years (95% CI 9.9 to 30.0 per 100 person-years).

CONCLUSIONS: One in four women with chlamydia infection at baseline retested positive, supporting recent recommendations to routinely retest chlamydia positives.

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