Evaluation and modification of the formalin-ether sedimentation technique

Formalin-ether sedimentation (MGL) is a well-known technique for the examination of faeces for parasites, but some recent reports have indicated that its efficiency is not as high as originally thought. We reevaluated the recovery efficiency of the original MGL (O-MGL) technique to modify it. We subsequently adopted the following modified MGL technique (M-MGL): filtration by three layers of gauze and washing, adjustment to pH 3, retreatment of plug, and use of 1.5 g of faeces. We also compared five faecal examination techniques (including the O-MGL and the M-MGL) for three parameters: recovery efficiency, sensitivity, and mean number of eggs detected. The highest sensitivity was obtained by the M-MGL (95%), followed by the commercially available kit (Kit; 90%), O-MGL (76%), Kato-Katz (KK; 57%), and direct smear (DS; 50%). The mean numbers of Ascaris lumbricoides eggs recovered by the techniques were in order M-MGL (148 eggs), Kit (97), O-MGL (41), KK (11), and DS (6). This M-MGL technique has the advantage not only of the above-mentioned three parameters, but also the ease of microscopic observation and the concentration index. The parameters of the O-MGL technique were not necessarily sufficient compared with the other techniques. It seems that the improved M-MGL technique in the present study is applicable for field surveys, particularly when the survey is done in areas of low parasite endemicity.