Page 292 - parasitology for medical and clinical laboratoryprofessionals

272 CHAPTER 12

PROCEDURE 12-4

(continued)

7. Place the slide(s) in a trichrome stain for at least 10 minutes.
8. Rinse in acid-alcohol (90 percent solution) for no more than 10 seconds. One to
three seconds may be sufficient.

9. Again, briefly rinse the slides by dripping them several times in two changes of
absolute methanol. This step should be used as a rinse for no more than 10 seconds.
Prolonged de-staining in this step causes poor differentiation in some organisms.
10. Place in xylene or xylene substitute for 5 minutes.
11. Mount with a 22 3 40 mm cover slip (no. 1 thickness). A mounting medium such
as Permount may be used to protect the slides but this step is optional.
12. Examine the smears using the oil immersion objective (1000 x). Read at least 100
fields of the slide. The reading time should be at least 10 minutes per slide.

Results and Report for Trichrome Staining Procedures
Any parasites observed should be reported by both genus and species if possible,
using the characteristics listed above as well as images provided throughout
the chapters of this book. The stages exhibited by the parasite (ova, larvae, cyst,
trophozoite) are important clinical items leading to appropriate treatment for the
victim of the infection. 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 if they are identifiable. Any other

identifiable elements such as artifacts or undigested materials may provide clues
as to a medical condition requiring treatment.
When trichrome staining methods are used, trophozoites, cysts, human tissue

cells and blood cells, and yeast or pseudohyphae are easily identifiable. Helminth ova

and some larvae often are excessively stained and the features of them are difficult to

visualize. Reportable artifacts are usually quantified as follows:
Average artifacts/
10 oil immersion fields Unit of report

Fewer than 2 Few
3–9 Moderate
Greater than 10 Many