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.
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.
Scott Lamontagne
D
D
Chlamydia Recall Study, HIV & STI Department, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, UK. scott.lamontagne@gmail.com.
Baster
Kathleen
K
Emmett
Lynsey
L
Nichols
Tom
T
Randall
Sarah
S
McLean
Louise
L
Meredith
Paula
P
Harindra
Veerakathy
V
Tobin
Jean M
JM
Underhill
Gillian S
GS
Graham Hewitt
W
W
Hopwood
Jennifer
J
Gleave
Toni
T
Ghosh
Ajit K
AK
Mallinson
Harry
H
Davies
Alisha R
AR
Hughes
Gwenda
G
Fenton
Kevin A
KA
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