Impact of Different Sampling Schemes for Decision Making in Soil-Transmitted Helminthiasis Control Programs

Area of Science:

• Epidemiology
• Public Health
• Infectious Diseases

Background:

• Preventive chemotherapy (PC) for soil-transmitted helminthiasis is crucial for disease control.
• Current guidelines rely on Kato-Katz (KK) fecal smears to estimate infection prevalence.
• KK-based egg counts exhibit high variability across samples and smears, impacting survey sensitivity.

Purpose of the Study:

• To evaluate the performance of different sampling schemes for soil-transmitted helminthiasis surveys within budget constraints.
• To provide evidence-based recommendations for optimizing KK survey methodologies.
• To inform policy decisions regarding the initiation and cessation of PC.

Main Methods:

• Analysis of population-level data from diverse epidemiological settings.
• Assessment of various sampling strategies (number of samples per person, smears per sample) under a fixed budget.
• Comparison of the statistical precision and sensitivity of different KK-based survey designs.

Main Results:

• Single-slide KK is effective for assessing moderate-to-heavy intensity infections and guiding the start/continuation of PC.
• More sensitive sampling schemes, involving multiple samples or smears, are necessary for decisions on stopping PC.
• Resource limitations necessitate a trade-off between the number of individuals screened and the sensitivity of prevalence estimates.

Conclusions:

• The choice of sampling scheme in KK surveys should be tailored to the specific policy decision (starting/continuing vs. stopping PC).
• Guidelines for soil-transmitted helminthiasis control should incorporate specific recommendations on optimal sampling strategies.
• Optimizing survey design is essential for accurate prevalence estimation and effective public health interventions.