RESUMEN
Examination of fecal specimens for detection of Giardia lamblia cysts is known to produce a high percentage of false negative results while it is generally believed that duodenal juice often contains trophozoites even when the stool examination is negative. The aim of this study was to compare the detection of trophozoites in duodenal aspirate with the findings of cysts in stool samples for the diagnosis of asymptomatic giardiasis. Forty five children with iron deficiency anemia (one to six years of age) were studied, 21 with giardiasis and 24 without giardiasis. For each subject, one to five stool samples were examined for cysts of Giardia lamblia employing the formol-ether concentration method. Duodenal juice from all children were examined for the presence of trophozoites of Giardia lamblia. Fecal excretion of cysts was demonstrated in 20 (95%) of the 21 patients with giardiasis; however, only nine (43%) exhibited the presence of trophozoites in their duodenal aspirates. In one child trophozoites were observed in the duodenal aspirate; but the parasitologic investigation was negative for cysts in the feces. All the children without giardiasis had at least three stool samples and duodenal aspirate negative for Giardia lamblia. In conclusion, fecal examination by formol ether concentration method exhibited a greater number of positive results than did the duodenal aspirate microscopy method in the diagnosis of giardiasis.