Objective:

Compare three enteroparasite concentration methods in human stool samples.

Methods:

A cross-sectional study was conducted of 154 stool samples divided into two groups: with parasites (n= 127) and without parasites (n= 27). The samples were subjected to three methods: direct parasitological examination, simple sedimentation and modified Ritchie's, and to microscopic observation in lugol and saline solution to a 40x increase.

Results:

In the non-parasite group the highest frequency in the presence of parasite structures was observed with the modified Ritchie's method (37%), followed by simple sedimentation (14.8%). In the parasite group a greater parasite load was obtained by Ritchie's method (3+ (15.8%) and 2+ (23.6%) than by simple sedimentation (3+ (10.2%) and 2+ (22.8%). The parasite species showing the highest frequency were Entamoeba coli (20.3%), Giardia lamblia (18.8%), Blastocystis hominis (15.9%) and Endomlimax nana (15.2%), whereas polyparasitism was found in 48.7% of the cases. The area under the curve (AUC) for the modified Ritchie's method, simple sedimentation technique and direct parasitological examination was 0.870, 0.648 and 0.796, respectively. In the modified Ritchie's method the AUC was greater in male (0.933) than in female subjects (0.92), as well as in subjects aged under 12 years (0.867) in comparison with people aged 12-37 years (0.833) and 18-39 years (0.800).

Conclusions:

The modified Ritchie's method has a high diagnostic yield and makes it possible to concentrate a larger number of intestinal parasites than the simple sedimentation method. Additionally, it has the advantage of using inputs of easy access and low toxicity, broadening the possibility of its implementation in parasitology laboratories.

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