Background: In England, screening for genital chlamydial infection has begun; however, screening frequency for women is not yet determined.
Aim: To measure chlamydia incidence and reinfection rates among young women to suggest screening intervals.
Methods: An 18-month prospective cohort study of women aged 16–24 years recruited from general practices, family planning clinics and genitourinary medicine (GUM) clinics: baseline-negative women followed for incidence and baseline-positive women for reinfection; urine tested every 6 months via nucleic acid amplification; and behavioural data collected. Extra test and questionnaire completed 3 months after initial positive test. Factors associated with infection and reinfection investigated using Cox regression stratified by healthcare setting of recruitment.
Results: Chlamydia incidence was mean (95% CI) 4.9 (2.7 to 8.8) per 100 person-years (py) among women recruited from general practices, 6.4 (4.2 to 9.8) from family planning clinics and 10.6 (7.4 to 15.2) from GUM clinics. Incidence was associated with young age, history of chlamydial infection and acquisition of new sexual partners. If recently acquiring new partners, condom use at last sexual intercourse was independently associated with lower incidence. Chlamydia reinfection was mean (95% CI) 29.9 (19.7 to 45.4) per 100/person-year from general practices, 22.3 (15.6 to 31.8) from family planning clinics and 21.1 (14.3 to 30.9) from GUM clinics. Factors independently associated with higher reinfection rates were acquisition of new partners and failure to treat all partners.
Conclusions: Sexual behaviours determined incidence and reinfection, regardless of healthcare setting. Our results suggest annual screening of women aged 16–24 years who are chlamydia negative, or sooner if partner change occurs. Rescreening chlamydia-positive women within 6 months of baseline infection may be sensible, especially if partner change occurs or all partners are not treated.
- GUM, genitourinary medicine
- NCSP, National Chlamydia Screening Programme
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↵i Note from principal author: Our study was designed during the original pilot of chlamydia screening in Portsmouth and the Wirral17 and implemented before the decision for a national screening programme that would exclude GU medicine and include men. We present results for women recruited from GU medicine, but recognise that the standards of care regarding chlamydial infection are dictated by different guidelines.
↵ii A separate manuscript in this journal presents the results of a transmission dynamic modelling study of the screening interval recommendations from this study to assess whether this recommended screening strategy, or others currently in use, can be used to achieve effective chlamydia control by reducing prevalence and transmission in the target population.24
Published Online First 18 October 2006
Funding: Funding for this study was provided by the Department of Health (England), Skipton House, 80 London Road, London SE1 6LH, UK. The opinions of the authors are reflective of the Chlamydia Recall Study Advisory Group and do not necessarily represent the views of the Department of Health (England).
Competing interests: None.
Guarantor statement: I, D Scott LaMontagne, had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Contributions: DSL was the lead investigator for the study from April 2003, supervised the study implementation, developed the plan and analysed study data in collaboration with statisticians and study coordinator, interpreted study findings, and was the principal author of the manuscript. KB was the statistician for the study, developed the plan and analysed study data in collaboration with the lead investigator and study coordinator, interpreted study findings, and coauthored the manuscript. LE was the study coordinator from March 2004, oversaw local data collection, collated and cleaned all study data, developed the plan and analysed study data in collaboration with lead investigator and statistician, interpreted study findings, and coauthored the manuscript. TN was the statistician during the revisions’ process, gratefully covering for KB while she was on maternity leave.
In addition to reviewing and commenting on final drafts of the manuscript, the following authors had these additional contributions: SR assisted in developing the local study protocol, and was lead clinician in Portsmouth for the study; LML was responsible for management of the study in Portsmouth, including subject recruitment, follow-up of recruits, patient and partner clinical management, and local data collection; PM was responsible for management of the study in Portsmouth, including subject recruitment, follow-up of recruits, patient and partner clinical management, and local data collection; VH assisted in developing the local study protocol and managed patients from GUM in the study; JMT assisted in developing the local study protocol and recruitment and management of patients from GUM in the study; GSU participated in protocol development and was responsible for the laboratory aspects of the study in Portsmouth; WGH performed local database administration, supervising implementation and integrity of the research database software; JH assisted in developing the local study protocol, and was lead clinician in the Wirral for the study; TG was responsible for management of the study in Wirral, including recruitment, follow-up, management of those screened positive and data collection; AKG supervised the local study implementation in the GU department of Arrowe Park Hospital, Birkenhead; HM assisted in developing the local study protocol and was responsible for laboratory testing the samples collected from study subjects in Birkenhead, and supervised the local data collection and database management; ARD coordinated the data management and was involved in data analysis and interpretation of results in the early stages of the study; GH was the original principal investigator and study manager (until March 2003) who developed the study idea, designed the study, wrote the protocol and acquired the funding; and KAF was an investigator and senior epidemiologist on the project, contributed to its design, implementation and was a previous guarantor of the study.