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Laboratory Procedures for Identifying Parasitic Organisms and Their Ova 265

9. Carefully “rim” the top layer to remove the debris on the edges of the upper
layer. Quickly and smoothly empty the supernatant into a container of disinfec-
tant only one time, taking care not to shake and disturb the “button” in the tip of
the centrifuge tube. If necessary, while holding the tube in an inverted position
for emptying, excess ethyl acetate that appears as bubbles can also be care-
fully removed with a cotton-tipped applicator stick.
10. Place a small amount of fecal sediment on a microscope slide and place a #1,
22-mm cover slide over each of the preparations.

11. The resultant preparations should be sufficiently transparent as to be able to
read newsprint through them.
12. An unstained and an iodine-stained specimen should be examined. The
unstained sample is necessary because cyst forms are refractile and can be
more easily observed if unstained with the iodine. The iodine solution enables
the visualization of nuclear detail and darkly stains any glycogen masses, which
are diagnostic for some protozoa.
13. Perform a thorough examination for both stained and unstained specimens
at low power, starting at one corner of the cover slip and making sweeping
moves both horizontally and vertically to cover the entire slide. The use of a
high-power objective with immersion oil may be used for closer examinations
of suspicious features but the slide should be sealed to avoid oil entering the
specimen underneath the cover glass.
14. Any parasites observed should be reported by both genus and species if pos-
sible and the stage of the parasite (ova, larvae, cyst, trophozoite). Cellular
components such as RBCs, WBCs, yeast, etc., are reported in a semiquantita-
tive form, as few moderate or many. Charcot-Leyden crystals are also reported
semiquantitatively.
Summary for Concentration of Fecal Specimens
To summarize the sedimentation method for concentrating fecal parasites and their
ova, this method is most effective for helminth ova, larvae, and protozoan oocysts
(Figure 12-5). The method requires the use of both ethyl acetate and formalin, both of
which may prove toxic to humans if not handled carefully.

Results and Report for Sedimentation Methods
Any parasites observed should be reported by both genus and species if possible and
the stage of the parasite (ova, larvae, cyst, trophozoite). Cellular components such as
RBCs, WBCs, yeast, etc., are reported in a semiquantitative form, as few, moderate, or
many. Charcot-Leyden crystals are also reported semiquantitatively. Any other iden-

tifiable elements such as artifacts or undigested materials may provide clues as to a
medical condition requiring treatment.