{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T22:38:09Z","timestamp":1787006289090,"version":"build-2736575974"},"reference-count":25,"publisher":"Oxford University Press (OUP)","issue":"Supplement_3","license":[{"start":{"date-parts":[[2021,4,27]],"date-time":"2021-04-27T00:00:00Z","timestamp":1619481600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000865","name":"Bill and Melinda Gates Foundation","doi-asserted-by":"publisher","award":["OPP1184344"],"award-info":[{"award-number":["OPP1184344"]}],"id":[{"id":"10.13039\/100000865","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003246","name":"Dutch Research Council","doi-asserted-by":"publisher","award":["016.Veni.178.023"],"award-info":[{"award-number":["016.Veni.178.023"]}],"id":[{"id":"10.13039\/501100003246","id-type":"DOI","asserted-by":"publisher"}]},{"name":"FWO International Coordination Action","award":["G0F4320N"],"award-info":[{"award-number":["G0F4320N"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2021,6,14]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>Control of soil-transmitted helminthiasis and schistosomiasis relies heavily on regular preventive chemotherapy. Monitoring drug efficacy is crucial to provide early warning of 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 of resources, it may lead to biased drug efficacy estimates.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>We performed a simulation study to assess the potential for bias when evaluating drug efficacy using the World Health Organization\u2013recommended survey design, and to identify alternative designs for evaluating drug efficacy that are less affected by bias. These designs were also based on selection of egg-positive individuals, but involve retesting them a second time at baseline and up to 2 times at follow-up. The utility of the different designs was compared fairly by constraining them to the same budget.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>The standard procedure of selecting egg-positive individuals can introduce a substantial positive bias in drug efficacy due to regression toward the mean, particularly when infection levels or drug efficacy are low. This bias was completely eliminated by using a second baseline sample, conditionally on the first sample being excluded from analysis. Precision of estimates can be improved by increasing the number of thick smears and\/or samples per person at follow-up, despite fewer individuals being tested within the same budget.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>We present optimized survey designs to monitor drug efficacy in field settings, which are highly relevant for sustained control of soil-transmitted helminths and schistosomiasis, as well as onchocerciasis and lymphatic filariasis.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1093\/cid\/ciab196","type":"journal-article","created":{"date-parts":[[2021,2,25]],"date-time":"2021-02-25T20:12:44Z","timestamp":1614283964000},"page":"S195-S202","source":"Crossref","is-referenced-by-count":17,"title":["Survey Design to Monitor Drug Efficacy for the Control of Soil-Transmitted Helminthiasis and Schistosomiasis"],"prefix":"10.1093","volume":"72","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4425-2264","authenticated-orcid":false,"given":"Luc E","family":"Coffeng","sequence":"first","affiliation":[{"name":"Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bruno","family":"Levecke","sequence":"additional","affiliation":[{"name":"Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jan","family":"Hattendorf","sequence":"additional","affiliation":[{"name":"Swiss Tropical and Public Health Institute, Basel, Switzerland"},{"name":"University of Basel, Basel, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Martin","family":"Walker","sequence":"additional","affiliation":[{"name":"Department of Pathobiology and Population Sciences and London Centre for Neglected Tropical Disease Research, Royal Veterinary College , Hatfield, United Kingdom"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matthew J","family":"Denwood","sequence":"additional","affiliation":[{"name":"Department of Veterinary and Animal Sciences, University of Copenhagen, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2021,6,14]]},"reference":[{"key":"2021070813544169900_CIT0001","volume-title":"Preventive chemotherapy in human helminthiasis. 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