[Evaluation of a technique of sedimentation in tubes]

The efficiency of sedimentation in test tubes for the detection of eggs of Ancylostomidae, Trichuris trichiura and Ascaris lumbricoides was tested in 80 mm-high columns of fecal suspensions. Dilutions of 2.0%, 1.5% and 1.0% were tested by using samples containing, respectively, 12.5, 25.0, 50.0, 100.0, 150.0 and 200.0 eggs per gram (epg) of each helminth under study. Efficiency was evaluated in terms of frequency of positive results and eggs per slide of the sediment (0.078 ml). Both the frequencies of positive results and egg counts per slide increased with epg values, but were not apparently dependent from suspension dilutions within the range assessed. Sediments of 1.0% fecal suspensions were positive in 80.0% or more of the cases for epg values of 150.0. It is inferred that dilution values are not critical. Thus, it is not necessary to determine fecal weights or volumes instrumentally. Considering overall results, it may be concluded that 1.0% fecal dilutions should be recommended for best results both in terms transparency of the preparations and chances of recovering eggs, particularly when egg counts are low.