Ova and Parasite (O&P) Examinations

Introduction | Macroscopic | Microscopic |

Microscopic Examination - Ova and Parasite Examination

Introduction | Direct Wet Smear | Concentration | Permanent Stained Smear

Direct Wet Smear

Results and Patient Reports

Protozoan trophozoites and/or cysts and helminth eggs and larvae may be seen and identified. In a heavy infection with Cryptosporidium parvum, oocysts may be seen in a direct smear; however, some type of modified acid-fast stain or immunoassay kit is normally used to detect these organisms, particularly when few oocysts are present. Oocysts of Isospora belli can also be seen in a direct smear. Spores of the microsporidia are too small, and the shape resembles other debris within the stool; therefore, they are not readily visible in a direct smear. Specialized stains (modified trichrome stains), or optical brightening agents are used for the identification of the microsporidia.

Motile trophozoites and protozoan cysts may or may not be identified to the species level (depending on the clarity of the morphology).
Examples: Giardia lamblia trophozoites and Entamoeba coli cysts.
Helminth eggs and/or larvae may be identified.
Examples: Ascaris lumbricoides eggs and Strongyloides stercoralis larvae.
Coccidian oocysts may be identified.
Example: Isospora belli oocysts
Artifacts and/or other structures may also be seen and reported as follows (note: these crystals and cells are quantitated; however, the quantity is usually assessed when the permanent stained smear is examined under oil immersion).
Examples: Moderate Charcot-Leyden crystals, few RBCs and moderate PMNs