Kasia StepniewskaElizabeth AshleySue J. LeeNicholas AnsteyKaren I. BarnesTran Quang BinhUmberto D'AlessandroNicholas P.J. DayPeter J. De VriesGrant DorseyJean Paul GuthmannMayfong MayxayPaul N. NewtonPiero OlliaroLyda OsorioRie N. PriceMark RowlandFrank SmithuisWalter R.J. TaylorFrançois NostenNicholas J. WhiteMahidol UniversityShoklo Malaria Research UnitMenzies School of Health ResearchUniversity of Cape TownCho Ray HospitalPrins Leopold Instituut voor Tropische GeneeskundeUniversity of OxfordLondon School of Hygiene &amp; Tropical MedicineAcademic Medical Centre, University of AmsterdamUniversity of California, San FranciscoInstitut de Recherche en Sciences de la SantéUganda Malaria Surveillance ProgramEpicentreInstitut de Veille SanitaireNational University of LaosOxford University Tropical Medicine Research CollaborationOrganisation Mondiale de la SanteHopitaux universitaires de GeneveCentra Internacional de Entrenamiento e Investigaciones MedicasImperial College Healthcare NHS Trust2018-09-242018-09-242010-02-15Journal of Infectious Diseases. Vol.201, No.4 (2010), 570-579002218992-s2.0-75749087199https://repository.li.mahidol.ac.th/handle/123456789/29769Parasite clearance data from 18,699 patients with falciparum malaria treated with an artemisinin derivative in areas of low (n = 14,539), moderate (n = 2077), and high (n = 2083) levels of malaria transmission across the world were analyzed to determine the factors that affect clearance rates and identify a simple in vivo screening measure for artemisinin resistance. The main factor affecting parasite clearance time was parasite density on admission. Clearance rates were faster in high-transmission settings and with more effective partner drugs in artemisinin-based combination treatments (ACTs). The result of the malaria blood smear on day 3 (72 h) was a good predictor of subsequent treatment failure and provides a simple screening measure for artemisinin resistance. Artemisinin resistance is highly unlikely if the proportion of patients with parasite densities of <100,000 parasites//μL given the currently recommended 3-day ACT who have a positive smear result on day 3 is <3%; that is, for n patients the observed number with a positive smear result on day 3 does not exceed (n + 60)/24. © 2010 by the Infectious Diseases Society of America. All rights reserved.Mahidol UniversityMedicineArticleSCOPUS10.1086/650301