title: Toward Measuring Schistosoma Response to Praziquantel Treatment with Appropriate Descriptors of Egg Excretion.
abstract: BACKGROUND
  The control of schistosomiasis emphasizes preventive chemotherapy with praziquantel, which aims at decreasing infection intensity and thus morbidity in individuals, as well as transmission in communities. Standardizing methods to assess treatment efficacy is important to compare trial outcomes across settings, and to monitor program effectiveness consistently. We compared customary methods and looked at possible complementary approaches in order to derive suggestions for standardizing outcome measures.
  
  
  RESULTS
  We analyzed data from 24 studies conducted at African, Asian, and Latin American sites, enrolling overall 4,740 individuals infected with Schistosoma mansoni, S. haematobium, or S. japonicum, and treated with praziquantel at doses of 40-80 mg/kg. We found that group-based arithmetic and geometric means can be used interchangeably to express egg reduction rates (ERR) only if treatment efficacy is high (>95%). For lower levels of efficacy, ERR estimates are higher with geometric than arithmetic means. Using the distribution of individual responses in egg excretion, 6.3%, 1.7% and 4.3% of the subjects treated for S. haematobium, S. japonicum and S. mansoni infection, respectively, had no reduction in their egg counts (ERR = 0). The 5th, 10th, and 25th centiles of the subjects treated for S. haematobium had individual ERRs of 0%, 49.3%, and 96.5%; the corresponding values for S. japonicum were 75%, 99%, and 99%; and for S. mansoni 18.2%, 65.3%, and 99.8%. Using a single rather than quadruplicate Kato-Katz thick smear excluded 19% of S. mansoni-infected individuals. Whilst the effect on estimating ERR was negligible by individual studies, ERR estimates by arithmetic means were 8% lower with a single measurement.
  
  
  CONCLUSIONS
  Arithmetic mean calculations of Schistosoma ERR are more sensitive and therefore more appropriate to monitor drug performance than geometric means. However, neither are satisfactory to identify poor responders. Group-based response estimated by arithmetic mean and the distribution of individual ERRs are correlated, but the latter appears to be more apt to detect the presence and to quantitate the magnitude of suboptimal responses to praziquantel.
authors.affiliation: UNICEF/UNDP/World Bank/WHO Special Programme on Research and Training in Tropical Diseases (TDR), World Health Organization, Geneva, Switzerland; Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: Piero L
authors.initials: PL
authors.lastname: Olliaro
authors.affiliation: Centre of Competence for Methodology and Statistics (CCMS), Luxembourg Institute of Health (LIH), Strassen, Luxembourg.
authors.forename: Michel
authors.initials: M
authors.lastname: Vaillant
authors.affiliation: Department of Biology, Division of Science and Mathematics, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
authors.forename: Aïssatou
authors.initials: A
authors.lastname: Diawara
authors.affiliation: Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire; Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire; Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Jean T
authors.initials: JT
authors.lastname: Coulibaly
authors.affiliation: University of Basel, Basel, Switzerland; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; Réseau International Schistosomoses, Environnement, Aménagement et Lutte (RISEAL-Niger), Niamey, Niger.
authors.forename: Amadou
authors.initials: A
authors.lastname: Garba
authors.affiliation: Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Keiser
authors.affiliation: Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America; Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Charles H
authors.initials: CH
authors.lastname: King
authors.affiliation: University of Basel, Basel, Switzerland; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, London, United Kingdom.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Knopp
authors.affiliation: Institut National de Recherche en Santé Publique, Bamako, Mali.
authors.forename: Aly
authors.initials: A
authors.lastname: Landouré
authors.affiliation: Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire; Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire.
authors.forename: Eliézer K
authors.initials: EK
authors.lastname: N'Goran
authors.affiliation: University of Basel, Basel, Switzerland; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Raso
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Alexandra U
authors.initials: AU
authors.lastname: Scherrer
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Sousa-Figueiredo
authors.affiliation: University of Basel, Basel, Switzerland; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; Center for Infectious Diseases and Travel Medicine, Department of Medicine, University Hospital Freiburg, Freiburg im Breisgau, Germany.
authors.forename: Katarina
authors.initials: K
authors.lastname: Stete
authors.affiliation: National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, People's Republic of China; Key Laboratory of Parasite and Vector Biology of the Chinese Ministry of Health, WHO Collaborating Center for Malaria, Schistosomiasis and Filariasis, Shanghai, People's Republic of China.
authors.forename: Xiao-Nong
authors.initials: XN
authors.lastname: Zhou
authors.affiliation: University of Basel, Basel, Switzerland; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
mesh_terms: D000818:Animals; D003627:Data Interpretation, Statistical; D005243:Feces / Q000469:parasitology; D016014:Linear Models; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010063:Ovum / Q000187:drug effects*; D011223:Praziquantel / Q000494:pharmacology*; D012547:Schistosoma / Q000187:drug effects*; D012552:Schistosomiasis / Q000453:epidemiology* / Q000517:prevention & control*
chemical_list: D011223:Praziquantel