Evaluating the impact and cost-effectiveness of chlamydia management strategies in Hong Kong: A modeling study

Abstract

Objectives: To illustrate the epidemiologic and cost-effectiveness impact of shifting the focus from population-based screening toward a targeted management approach for genital chlamydia infection.

Design: Modeling study, implementing an individual-based, stochastic, dynamic network model.

Setting: Hong Kong.

Population: A hypothetical sample network of 10,000 people with a partnership distribution based on Hong Kong's sexually active population of reproductive age (age 18-49 years).

Interventions: In this study, we present several scenarios with different implementations of universal vs. targeted screening (based on partner numbers). We also explored the impact of (1) screening only, (2) screening plus expedited partner therapy, and (3) screening plus partner testing.

Primary outcome measures: Change of chlamydia prevalence before and after implementing the different strategies. The cost-effectiveness analysis reports total direct cost from a health provider perspective, the QALYs gained, and incremental cost-effectiveness ratios (ICER).

Results: In comparing the effects of universal screening only and targeted screening of the high-risk population, the mean prevalence during the 10th year of intervention was 2.75 ± 0.30% and 2.35 ± 0.21%, respectively (compared with 3.24 ± 0.30% and 3.35 ± 0.21% before the interventions, respectively). The addition of contact tracing to the latter targeted screening scenario reduces the mean prevalence during the 10th year of intervention to 1.48 ± 0.13% (compared with 3.31 ± 0.33% at baseline) in the best-case of testing before treatment and maximal contact-tracing effectiveness (40%). Overall, the most effective scenarios were those for which interventions focused on the high-risk population defined by the number of partners, with contact tracing included. The ICER for targeted screening with contact tracing at 20% and 40% efficiency was $4,634 and $7,219 per QALY gained, respectively (10-year time horizon). Expedited partner therapy did not significantly impact overall chlamydia prevalence and caused overtreatment.

Conclusions: Our study suggests that targeted screening with strengthened contact tracing efforts is the most cost-effective strategy to reduce the prevalence of chlamydia in Hong Kong.

Keywords: chlamydia; cost-effectiveness; dynamic network models; economic evaluation; stochastic model.

Figure 1

Comparison of program effects between universal screening with 10% and 30% of the population screened per year (1–3 and 4–6 respectively) and targeted screening according to the number of partners with 10% of the population screened per year (7–9). (1,4,7) show prevalence results over 100 simulations (blue) and the mean percentage of prevalence (red). (2,5,8) present t the number of doses provided per month, where the individual had a chlamydia infection (green) or was not infected (red). (3,6,9) show the average number of people screened per day.

Figure 2

Summary of main results obtained from targeted: follow-up screening simulations, varying follow-up waiting periods, scenarios Bi (1), Bii (2), Biii (3), the modeled percentage of symptomatic population present in the model, as well as the addition of one version of partner tracing on scenarios Biv (4), Ci (5) and Cii (6).

Figure 3

Results from the scenarios targeting the high-risk population as defined by the number of partners. Section (1) corresponds to scenario Di. Sections (2–5) present the prevalence results from scenarios Dii-Dv and (6–9) are from scenarios Ei-Eiv.