The diagnosis of Blastocystis hominis cysts in human faeces.

Blastocystis hominis cysts in faeces can be concentrated on Ficoll column. They are pleomorphic in shape having a mean diameter of 6.65 microns (S.D. = 2.32). They may or may not have a membranous layer surrounding them. The membranous layer tends to come off with pressure or dying of the specimen and corresponds to the fibrillar layer observed under the electron microscope. The Ficoll concentration technique is also useful for concentrating other protozoan cysts.