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are good and the results of the patient’s specimen are presumed valid.
(1) Positive - any trace of blue on or at the edge of the smears.
(2) Negative - no detectable blue on or at the edge of the smears.
NOTE: Refer to the manufacturer’s instructions for specific times and quantitation.
The principle of this test is the general reaction:
Hemoglobin reacts with pseudo peroxide, yielding H 2 O 2 , which reacts with benzidine orthotoluidine
guaiac in the presence of oxygen to yield the color blue.
- Record all results on the laboratory request form.
Lab Procedure: Feces for Ova and Parasites
18D Skills and Training ManualWhen: To examine a stool sample for the presence of parasites and their eggs.
What You Need: A properly collected stool specimen: 10% formalin, ethyl acetate, Lugol’s iodine or
Merthiolate-Iodine-Formalin (MIF), toluene or xylene, paper cups, water, transfer pipets, graduated cylinders,
applicator sticks, centrifuge, centrifuge tubes, laboratory funnel, 4” x 4” gauze, slides, coverslips, logbook,
and a lab request form.
What To Do:
- Concentrate the sample.
a. Strain about 3 ml of the specimen suspension through either the disposable filtering device or 2
layers of wet gauze placed in the funnel into a 15 ml conical centrifuge tube.
b. Fill the tube to 12 ml with 10% formalin.
c. Centrifuge at 2000 rpm for 5 minutes.
d. Remove the tubes and pour off the supernatant.
e. Prepare slides for acid-fast bacteria (AFB) staining by placing 1 drop of the sediment on a glass
slide and allowing it to air dry for recovery of cryptosporidium.
f. Add formalin to the 8 ml mark on the tube and resuspend the sediment.
WARNING: Formalin may be fatal if swallowed or harmful if inhaled. Exposure may create a cancer
risk and may cause blindness. Keep away from heat, sparks, or flame. Avoid breathing vapor. Use
only with adequate ventilation. Wash thoroughly after handling.
g. Add ethyl acetate to the 12 ml tube, stopper the tube, and vortex.
WARNING: Ethyl acetate is flammable. Keep away from heat, sparks, or flame. It is harmful if
swallowed or inhaled. Use only with adequate ventilation. Avoid contact with eyes. Wash thoroughly
after handling.
h. Allow the tube to stand for 3 minutes.
i. Centrifuge at 2000 rpm for 5 minutes.
j. Ream the plug with an applicator stick and decant the supernatant.
CAUTION: Do not allow debris or ethyl acetate to contaminate the sediment. - Perform the microscopic examination.
a. Transfer 1 drop of the sediment to a glass slide.
b. Add 1 drop of Lugol’s iodine and cover with a coverslip.
c. Scan the whole slide on low (10x) power.
d. Identify using high-dry (40x) objective. Scan at least 75 fields under high dry. - Report the results.
a. If organisms are recovered, report by genus and species name.
b. If none are seen, report “No ova/ parasites seen”.
The following steps relate to examination for pinworms, “Scotch tape test”. - Prepare the collection slide.
a. Anchor one end of the cellulose tape to the underside of the microscope slide.