Insights into the timing of repeated testing after treatment for Chlamydia trachomatis: data and modelling study.
OBJECTIVE
The objective of this study was to determine the optimal time interval for a repeated Chlamydia trachomatis (chlamydia) test.


METHODS
The authors used claims data for US women aged 15-25 years who were enrolled in commercial health insurance plans in the MarketScan database between 2002 and 2006. The authors determined the numbers of initial positive and negative tests that were followed by a repeated test and the positivity of repeated tests. The authors used a dynamic transmission pair model that reflects the partnership formation and separation processes in 15-25 year olds to determine the time course of repeated infections in women under different levels of notifying the current partner. The authors then explored the additional impact of repeated testing uptake on reducing chlamydia prevalence.


RESULTS
40% (4949/12 413) of positive tests were followed by a repeated test compared with 22% (89 119/402 659) of negative tests at any time. Positivity of repeated tests followed by an initial positive test was high: 15% (736) after a positive test versus 3% (2886) after a negative test. The transmission model showed a peak in repeated infections between 2 and 5 months after treatment. For a chlamydia testing uptake of 10% per year, the additional impact of repeated testing on reducing chlamydia population prevalence was modest.


CONCLUSIONS
The mathematical model predictions support the recommended interval for repeat chlamydia testing. This study provides information that can be used to design randomised controlled trials to determine more effective interventions to prevent chlamydial reinfection.
Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland. jheijne@ispm.unibe.ch
Janneke Cornelia Maria
JC
Heijne
Sereina Annik
SA
Herzog
Christian Lorenz
CL
Althaus
Guoyu
G
Tao
Charlotte Kathleen
CK
Kent
Nicola
N
Low
D000293:Adolescent; D000328:Adult; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D005260:Female; D006801:Humans; D008219:Lymphogranuloma Venereum / Q000175:diagnosis* / Q000188:drug therapy* / Q000453:epidemiology; D015233:Models, Statistical; D012725:Sexual Behavior; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult