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ABSTRACT: OBJECTIVE: To estimate the impact of increased testing of asymptomatic young people for chlamydia on infection prevalence in England. METHODS: An age and sex-stratified deterministic model including three sexual activity groups and the effect of notifying partners of treated individuals was used to describe chlamydia transmission in England. Model predictions were fitted to national chlamydia prevalence data for the year 2000 to estimate unknown parameters, including the transmission rate per partnership. Uncertainty in these parameters was captured by rejection sampling. The model estimated the effects of increased testing using observed levels of testing and proportions testing positive for chlamydia between 2000/2001 and 2010/2011, and scenario projections until 2013/2014. RESULTS: Prevalence was assumed to be at equilibrium in 2000 and found to be 4.5% among 16-24-year-olds. Estimates suggest that population prevalence was 28% lower in 2010/2011 than it would have been had no testing increases occurred. This estimate was insensitive to baseline prevalence but depended on the assumed reinfection risk and effective notification rate of partners of treated individuals. Annual reductions of 2.4% and 1.4% in prevalence after 2010/2011 were predicted if testing rates thereafter increased to 45% of 16-24-year-olds or remained unchanged at 35%, respectively. CONCLUSIONS: Based on available data, the modelling suggests that the current level of chlamydia testing in England is reducing prevalence among 16-24-year-olds. Up-to-date data on population prevalence are needed to confirm this. Investigating the impact of improving partner notification and treatment requires further work.
Sexually transmitted infections 06/2012; DOI:10.1136/sextrans-2011-050126 · 3.40 Impact Factor