[The microwave oven for drying thick blood smears. Benefits and limits for microscopic observation of Plasmodium falciparum trophozoites and gametocytes].
The micro-wave oven permits a rapid drying of thick blood smears classically used for parasitological malaria diagnosis. In order to evaluate this type of drying on the microscopic reading, a study was carried out in an hyperendemic area of malaria with 382 asymptomatic volunteers of all ages. Two thick smears were made for each volunteer, one immediately dried with a micro-wave oven for one minute, the second dried in the open air without any intervention. A single microscopist examined all the thick smears. The observation of Plasmodium falciparum trophozoites differed significantly between the two methods, the prevalence was 50% by normal drying versus 41% by the micro-wave oven. The geometric mean of the trophozoite number for positive thick smears was significantly lower with the micro-wave oven. When the parasitological density with normal drying was lower than 200 trophozoites/microliter of blood, 54% of results were wrongly negative with the micro-wave oven. On the other hand, the observation of P. falciparum gametocytes was significantly 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 observation and counting of P. falciparum gametocytes.
Institut français de recherche scientifique pour le développement en coopération (ORSTOM), Yaoundé, Cameroun.
G
G
Le Goff
J Y
JY
Le Hesran
V
V
Robert
D000818:Animals; D001769:Blood / Q000469:parasitology*; D005898:Glass; D006801:Humans; D008853:Microscopy; D008872:Microwaves; D010963:Plasmodium falciparum / Q000254:growth & development* / Q000302:isolation & purification*
Le four à micro-ondes pour le séchage des gouttes épaisses. Intérêt et limites dans l'observation microscopique des trophozoïtes et des gamétocytes de Plasmodium falciparum.