title: Incidence and reinfection rates of genital chlamydial infection among women aged 16-24 years attending general practice, family planning and genitourinary medicine clinics in England: a prospective cohort study by the Chlamydia Recall Study Advisory Group.
abstract: BACKGROUND
  In England, screening for genital chlamydial infection has begun; however, screening frequency for women is not yet determined.
  
  
  OBJECTIVE
  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.
authors.affiliation: Chlamydia Recall Study, HIV & STI Department, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, UK. scott.lamontagne@gmail.com.
authors.forename: D
authors.initials: D
authors.lastname: Scott Lamontagne
authors.forename: Kathleen
authors.initials: K
authors.lastname: Baster
authors.forename: Lynsey
authors.initials: L
authors.lastname: Emmett
authors.forename: Tom
authors.initials: T
authors.lastname: Nichols
authors.forename: Sarah
authors.initials: S
authors.lastname: Randall
authors.forename: Louise
authors.initials: L
authors.lastname: McLean
authors.forename: Paula
authors.initials: P
authors.lastname: Meredith
authors.forename: Veerakathy
authors.initials: V
authors.lastname: Harindra
authors.forename: Jean M
authors.initials: JM
authors.lastname: Tobin
authors.forename: Gillian S
authors.initials: GS
authors.lastname: Underhill
authors.forename: W
authors.initials: W
authors.lastname: Graham Hewitt
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hopwood
authors.forename: Toni
authors.initials: T
authors.lastname: Gleave
authors.forename: Ajit K
authors.initials: AK
authors.lastname: Ghosh
authors.forename: Harry
authors.initials: H
authors.lastname: Mallinson
authors.forename: Alisha R
authors.initials: AR
authors.lastname: Davies
authors.forename: Gwenda
authors.initials: G
authors.lastname: Hughes
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Fenton
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000553:Ambulatory Care; D002690:Chlamydia Infections / Q000453:epidemiology*; D002692:Chlamydia trachomatis; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D005193:Family Planning Services; D005194:Family Practice; D005260:Female; D006801:Humans; D015994:Incidence; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D012747:Sexual Partners