Tips and Pitfalls!

1. If using a 50 or 60X oil immersion lens, remember to review the stained fecal smear using the 100X oil immersion lens; some of the protozoa are too small to see without the higher magnification lens.
2. Trophozoites tend to stain lighter than cysts (exception would be Entamoeba coli cysts that generally do not fix/stain well).
3. Cyst measurements will be 1 to 1.5 microns smaller in the stained fecal smear than in wet preparations (shrinkage due to dehydration steps in staining process). You may even see "halos" around the cyst wall. The organism measurement should include the area of the clear halo.
4. Identification to the species level can be very difficult, if not impossible, on the wet mount (direct wet mount, concentration wet mount); with few exceptions, tentative identification of protozoa will need to be confirmed by examination of the permanent stained smear.