THE MICROWAVE-OVEN FOR THE DRYING OF THICK BLOOD SMEARS - ADVANTAGES AND DRAWBACKS IN THE MICROSCOPIC OBSERVATION OF PLASMODIUM-FALCIPARUM TROPHOZOITES AND GAMETOCYTES

The micro-wave oven permits a rapid drying of thick blood smears class ically used for parasitological malaria diagnosis. In order to evaluat e this type of drying on he microscopic reading, a study was carried o ut in an hyperendemic area of malaria with 382 asymptomatic volunteers of all ages. Two thick smears were made for each volunteer; one immed iately dried with a micro-wave oven for one minute, the second dried i n the open air without any intervention. A single microscopist examine d all the hick smears. The observation of Plasmodium falciparum tropho zoites differed significantly between the two methods, the prevalence was 50% by normal drying versus 41% by the micro-wave oven. The geomet ric mean of the trophozoite number for positive thick smears was signi ficantly lower with the micro-wave oven. When the parasitological dens ity with normal drying was lower than 200 trophozoites/mu l of blood, 54% of results were wrongly negative with the microwave oven. On the o ther hand, the observation of P. falciparum gametocytes was significan tly facilitated after drying with the micro-wave oven; the prevalence was 8% with normal drying versus 12% by micro-wave oven. In conclusion , the use of the micro-wave oven for the drying of thick smears is not recommended for malaria diagnosis although it improves the observatio n and counting of P. falciparum gametocytes.