Survey Design to Monitor Drug Efficacy for the Control of Soil-Transmitted Helminthiasis and Schistosomiasis

Abstract Background Control of soil-transmitted helminthiasis and schistosomiasis relies heavily on regular preventive chemotherapy. Monitoring drug efficacy is crucial to provide early warning treatment failures. The World Health Organization (WHO) recommends a survey design in which only egg-positive individuals are retested after treatment. Although this practice makes more efficient use resources, it may lead biased estimates. Methods We performed simulation study assess the potential for bias when evaluating using Organization–recommended design, identify alternative designs that less affected by bias. These were also based selection individuals, but involve retesting them second time at baseline up 2 times follow-up. utility different was compared fairly constraining same budget. Results standard procedure selecting can introduce substantial positive due regression toward mean, particularly infection levels or low. This completely eliminated sample, conditionally first sample being excluded from analysis. Precision estimates be improved increasing number thick smears and/or samples per person follow-up, despite fewer tested within Conclusions present optimized monitor field settings, highly relevant sustained control helminths schistosomiasis, as well onchocerciasis lymphatic filariasis.