Starting and stopping preventive chemotherapy (PC) for soil-transmitted helminthiasis is typically based on the prevalence of infection as measured by Kato-Katz (KK) fecal smears. Kato-Katz-based egg counts can vary highly over repeated stool samples and smears. Consequentially, the sensitivity of KK-based surveys depends on the number of stool samples per person and the number of smears per sample. Given finite resources, collecting multiple samples and/or smears means screening fewer individuals, thereby lowering the statistical precision of prevalence estimates. Using population-level data from various epidemiological settings, we assessed the performance of different sampling schemes executed within the confines of the same budget. We recommend the use of single-slide KK for determining prevalence of moderate-to-heavy intensity infection and policy decisions for starting and continuing PC; more sensitive sampling schemes may be required for policy decisions involving stopping PC. Our findings highlight that guidelines should include specific guidance on sampling schemes.

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Keywords fecal egg counts, Kato-Katz, moderate-to-heavy infection, prevalence, soil-transmitted helminths
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Journal The Journal of Infectious Diseases
Coffeng, L.E, Malizia, V. (Veronica), Vegvari, C. (Carolin), Cools, P. (Piet), Halliday, K.E. (Katherine E.), Levecke, B. (Bruno), … de Vlas, S.J. (2020). Impact of Different Sampling Schemes for Decision Making in Soil-Transmitted Helminthiasis Control Programs. The Journal of Infectious Diseases, 221(5), S531–S538. doi:10.1093/infdis/jiz535