Concentration: Introduction

Fecal concentration has become a routine procedure as a part of the complete ova and parasite examination for parasites and allows the detection of small numbers of organisms that may be missed by using only a direct wet smear. There are two types of concentration procedures, sedimentation and flotation, both of which are designed to separate protozoan organisms and helminth eggs and larvae from fecal debris by centrifugation and/or differences in specific gravity.

Sedimentation methods (using centrifugation) lead to the recovery of all protozoa, oocysts, spores, eggs, and larvae present; however, the preparation contains more debris. If one technique is selected for routine use, the sedimentation procedure is recommended as being the easiest to perform and least subject to technical error.