The Philadelphia High-School STD Screening Program: key insights from dynamic transmission modeling

The Philadelphia high-school STD Screening Program (PHSSP) represents an innovative approach to screening-based control of Chlamydia trachomatis infection. The program has been associated with significant reductions in Chlamydia trachomatis prevalence in young females in Philadelphia. We sought to assess program cost-effectiveness in a manner that allowed us to quantify the impact of including males students in the screened population.

We created a dynamic transmission model using a susceptible-infectious-resistant-susceptible framework. The model was parameterized using PHSSP program data, supplemented by available data from the medical and public health literature, and was used to project the impact of screening on disease burden, quality adjusted survival, and costs.

A well-calibrated model suggests that high-school based screening is highly cost-effective in the Philadelphia context. Five important insights are gained through dynamic transmission modeling of the PHSSP: (i) the importance of screening males can be appreciated using a dynamic transmission model; (ii) the attractiveness of screening males is inversely related to equilibrium prevalence in males; (iii) including males enhances both effectiveness and economic attractiveness of screening; (iv) rebound in prevalence does not greatly diminish the cost-effectiveness of screening; and (v) increasing program expenditures via increased screening coverage decreases net societal costs, due to diminished disease transmission.

The current PHSSP is highly cost-effective relative to other commonly accepted interventions. Effectiveness and cost-effectiveness of this program are enhanced by including males. This, and other important attributes of the program, is best appreciated when a dynamic transmission model is used for program evaluation.