Ova and Parasite (O&P) Examinations

Topic

Comments

Principle

To provide contrasting colors for both the background debris and parasites present; designed to allow examination and recognition of detailed organism morphology under oil immersion examination (100X objective for a total magnification of 1000X). Primarily designed to allow recovery and identification of the intestinal protozoa.

Specimen

Any stool specimen that is fresh or preserved in formalin, PVA (mercury- or non-mercury-based), SAF, MIF or newer single vial system fixatives.

Reagents

Trichrome, iron-hematoxylin, modified iron-hematoxylin, polychrome IV, or chlorazol black E stains and their associated solutions; dehydrating solutions (alcohols and xylenes); mounting fluid optional.

Examination

Oil immersion examination of at least 300 fields; additional fields may be required if suspect organisms have been seen in the wet preparations from the concentrated specimen.

Results and Laboratory Reports

The majority of the suspect protozoa and/or human cells could be confirmed using the permanent stained smear. These reports should be categorized as "final" and would be signed out as such (where the direct wet smear and concentration examination would provide "preliminary" results).

Procedure Notes and Limitations

The most commonly used stains include trichrome and iron-hematoxylin. Unfortunately, helminth eggs and larvae will take up too much stain and usually can not be identified from the permanent stained smear. Also, coccidian oocysts and microsporidian spores usually require other staining methods for identification. Permanent stained smears are normally examined under oil immersion examination (1000X), and low or high dry power are not recommended. Confirmation of the intestinal protozoa (both trophozoites and cysts) is the primary purpose of this technique.