Background Chlamydia testing rates are low, with only about a third of sexually active young women tested at clinical encounters. Even fewer sexually active female adolescents are tested. Interventions to increase testing coverage have been moderately successful. In this study, we assessed the relative health and economic outcomes of patient-directed, universal, opt-out testing for women aged 15–24 years in the United States who have at least one clinical encounter each year when compared with current testing (30% coverage).

Methods We used a basic dynamic compartmental model that included two groups based on their self-reported sexual activity in the past 12 months, with 72% being sexually active and 28% inactive. For our base case analysis, we assumed a 75% uptake of the intervention by sexually active women and 5% by sexually inactive women. All model parameters were obtained from the literature. The model was calibrated to produce a pre-intervention prevalence close to the national burden for those aged 15–24 years in the United States (≈2.5%). Health outcomes were measured in quality-adjusted life years (QALYs).

Results Based on our model (including health insurance coverage and utilisation rates), the estimated effective annual testing rate increased to approximately 52%, and overall chlamydia prevalence decreased by 60% to ≈1% over a three-year period. The estimated cost per QALY gained was $1372. When we assumed an uptake rate ≥ 85%, the overall prevalence decreased to zero.

Conclusion The universal, opt-out testing intervention was cost-effective because it did not require additional costs over and above testing and treatment. Our exploratory analyses suggest that implementation of opt-out testing of young women during clinical encounters might substantially increase testing coverage of sexually active young women. However, even with a higher uptake, testing gaps would remain because many women might not have health insurance coverage, or not utilise healthcare.