Browsing by Author "Mayxay, Mayfong"

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    Assessment of therapeutic responses to gametocytocidal drugs in Plasmodium falciparum malaria
    (2014-12-09) White, Nicholas J; Ashley, Elizabeth A; Recht, Judith; Delves, Michael J; Ruecker, Andrea; Smithuis, Frank M; Eziefula, Alice C; Bousema, Teun; Drakeley, Chris; Chotivanich, Kesinee; Imwong, Mallika; Pukrittayakamee, Sasithon; Prachumsri, Jetsumon; Chu, Cindy; Andolina, Chiara; Bancone, Germana; Hien, Tran T; Mayxay, Mayfong; Taylor, Walter R; von Seidlein, Lorenz; Price, Ric N; Barnes, Karen I; Djimdé, Abdoulaye; ter Kuile, Feiko; Gosling, Roly; Chen, Ingrid; Dhorda, Mehul J; Stepniewska, Kasia; Guérin, Philippe; Woodrow, Charles J; Dondorp, Arjen M; Day, Nicholas P; Nosten, Francois H
    Abstract Indirect clinical measures assessing anti-malarial drug transmission-blocking activity in falciparum malaria include measurement of the duration of gametocytaemia, the rate of gametocyte clearance or the area under the gametocytaemia-time curve (AUC). These may provide useful comparative information, but they underestimate dose-response relationships for transmission-blocking activity. Following 8-aminoquinoline administration P. falciparum gametocytes are sterilized within hours, whereas clearance from blood takes days. Gametocytaemia AUC and clearance times are determined predominantly by the more numerous female gametocytes, which are generally less drug sensitive than the minority male gametocytes, whereas transmission-blocking activity and thus infectivity is determined by the more sensitive male forms. In choosing doses of transmission-blocking drugs there is no substitute yet for mosquito-feeding studies.
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    The relationship between the haemoglobin concentration and the haematocrit in Plasmodium falciparum malaria
    (BioMed Central Ltd, 2008) Lee, Sue; Stepniewska, Kasia; Anstey, Nicholas; Ashley, Elizabeth; Barnes, Karen; Binh, Tran; D'Alessandro, Umberto; Day, Nicholas; de Vries, Peter; Dorsey, Grant; Guthmann, Jean-Paul; Mayxay, Mayfong; Newton, Paul; Nosten, Francois; Olliaro, Piero
    BACKGROUND:Malaria is a very important cause of anaemia in tropical countries. Anaemia is assessed either by measurement of the haematocrit or the haemoglobin concentration. For comparisons across studies, it is often necessary to derive one measure from the other. METHODS: Data on patients with slide-confirmed uncomplicated falciparum malaria were pooled from 85 antimalarial drug trials conducted in 25 different countries, to assess the haemoglobin/haematocrit relationship at different time points in malaria. Using a linear random effects model, a conversion equation for haematocrit was derived based on 3,254 measurements from various time points (ranging from day 0 to day 63) from 1,810 patients with simultaneous measurements of both parameters. Haemoglobin was also estimated from haematocrit with the commonly used threefold conversion. RESULTS: A good fit was obtained using Haematocrit = 5.62 + 2.60 * Haemoglobin. On average, haematocrit/3 levels were slightly higher than haemoglobin measurements with a mean difference (+/- SD) of -0.69 (+/- 1.3) for children under the age of 5 (n = 1,440 measurements from 449 patients). CONCLUSION: Based on this large data set, an accurate and robust conversion factor both in acute malaria and in convalescence was obtained. The commonly used threefold conversion is also valid.