STEP 4: Scan the whole preparation under low power and confirm findings under the
high dry objective. If known or suspected microfilariae are found, proceed to
fix and stain the remaining sediment.
STEP 5: Smear the remaining sediment over a slide. Let it air-dry and fix in alcohol-
ether mixture for 10 minutes. Allow it to dry.
STEP 6: Cover the slide with Ehrlich's hematoxylin solution for 40 to 60 minutes.
Follow this with a quick rinse (several dips) in a 0.05 percent hydrochloric
acid solution. Wash it in gently running tap water until the blue color appears
in the film. Air-dry the smear and examine it under low power on the
microscope. Confirm the results under high dry objective.
(3) Staining reaction. With this stain, the nuclei will stand out sharply and
the sheaths, if present, will be clearly visible. Alternate stains may be used (such as
Giemsa's stain, methylene blue, or other hematoxylin procedures).
f. Parasitized Cell Count. For the determination of parasitemia in malaria,
primarily two methods are used: a direct method and an indirect method. The more
practical indirect method requires counting leucocytes (as numerical indicators) and
parasitized red blood cells. The more accurate direct method requires counting the
parasitized and non-parasitized red blood cells.
(1)
Indirect method (leukocyte count).
(a) A leukocyte count is performed on the specimen.
(b) A thin film smear is then made and stained with Giemsa's stain.
(c) Parasitized red cells and the leukocytes are counted until at least
200 parasitized cells are counted.
(d) From the leukocyte count, calculations of the number of parasites
per millimeter can be made.
(2)
Direct method.
(a) A red blood cell count is performed on the specimen.
(b) A thin film smear is then made and stained with Giemsa's stain.
(c)
A direct count is made of all the red cells in a given area.
(d) The ratio of infected cells to normal red cells is determined.
MD0841
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