Purpose: Genital Chlamydia infection is the most widespread bacterial sexually transmitted disease in the United State, accounting for annual costs that exceed $2 billion. Since most infections are asymptotic, screening for CT and early treatment are the most promising public health interventions to prevent acute pelvic inflammatory disease (PID) and more serious long-term complications. The well-accepted clinical guidelines recommended annual screening for sexually active women before age of 25 years. Our objective is to assess the cost-effectiveness of alternative strategies that differ by the start/end screening age and screening frequency.
Method: We developed a state transition model to capture the system dynamics of CT transmission, screening, diagnosis, and treatment for a representative cohort of sexually active U.S. women from 15 to 25, incorporating age-specific transmissions, treatment effectiveness, and acute and long-term complications. The outcome measures included incidence of clinical events (e.g., acute PID) and per-capita societal cost. Our data were acquired from published literature. Model validation was conducted with respect to the percentage of positive CT test results and cumulative incidence of acute PID. In the simulation experiments we conducted, we varied the start screening age from 15 to 17, and the end age from 25 to 23. For each combination of optional start and end ages, we varied the screening frequency from once a year to once a quarter year, as quarterly screening is believed to match the maximal public health resource level on CT screening.
Results:
· Two of the 36 baseline experiments suggested that alternative screening strategies can be cost-saving and more effective compared to the well-accepted clinical guideline. Such two strategies recommended deceasing screening duration and modestly increasing screening frequency.
· Among other tested strategies, 8 were cost-saving, and the rest were cost-effective, with $5120 per acute PID case averted on average.
· The results were the most sensitive to the CT transmission risk and the effectiveness of acute PID treatment.
Conclusions: Screening young women annually can be improved by altering the start/end screening age and screening frequency. A limitation of the study was the uniform assumption on the age and CT transmission of the cohort. Given that CT transmission risk varies by age, carefully designed age-structured target screening strategies would become appealing to the policy makers.
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