Purpose: High prevalence of infection with Chlamydia trachomatis in Philadelphia teens led to the introduction of system-wide urine-based anonymous screening in the city's public schools in 2002-03. Prevalence in teens has declined since screening was introduced. Existing assessments of cost-effectiveness of C. trachomatis screening disregard the transmissibility of this pathogen; we sought to assess cost-effectiveness of screening male and female students using a dynamic transmission model.

Methods: A dynamic transmission model was constructed using cross-sectional prevalence data, based on the simplifying assumption that the Philadelphia Chlamydia epidemic was at equilibrium when screening was initiated. The model was calibrated to reproduce the observed changes in prevalence of Chlamydia that followed the introduction of screening. Data on test costs were derived directly from the screening program; estimated costs of complications of infection (e.g., pelvic inflammatory disease, infertility, etc.) were abstracted from the published medical literature.

Results: A model based on non-assortative mixing and 20% reduction in infection in students identified through screening reproduced observed changes in population prevalence of Chlamydia that occurred after screening was introduced. Screening both males and females resulted in a greater reduction in pelvic inflammatory disease and related sequelae than screening either gender alone. All screening strategies (including screening only males) resulted in net societal cost-savings relative to no screening, but the greatest savings were seen when both genders were screened. Screening was cost saving even when initial prevalence in females was as low as 4%, but the number of years required to “break even” financially increased as prevalence declined.

Conclusions: Using a modeling approach that accounts for transmissibility, cost-savings associated with Chlamydia screening are projected to increase when screening is extended to males. Furthermore, screening is projected to be cost-saving at relatively low prevalence thresholds when transmissibility is considered.