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The ring-stage survival assay (RSA) is a powerful tool for phenotyping artemisinin-resistant Plasmodium falciparum but requires experienced microscopists to count viable parasites among 10,000 erythrocytes in Giemsa-stained thin blood smears. Here we describe a rapid flow cytometric assay that accurately counts viable parasites among 250,000 erythrocytes in suspension. This method performs as well as light microscopy and can be used to standardize the collection of RSA data between research groups in laboratory and field settings.

Original publication




Journal article


Antimicrobial agents and chemotherapy

Publication Date





4938 - 4940


Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.


Erythrocytes, Humans, Plasmodium falciparum, Artemisinins, Antimalarials, Fluorescent Dyes, Biological Assay, Flow Cytometry, Staining and Labeling, Parasitic Sensitivity Tests, Cell Survival, Life Cycle Stages, Half-Life