Normal WBC, no eosinophilia
Stool O&P
Motile trophozoites or cysts
Able to diagnose infection readily in acute illness
More difficult to diagnose in chronic or asymptomatic infection
Antigen testing with ELISA, DFA, etc starting to replace microscopic examination with similar cost 
Suspect protozoan illness in patients with diarrhea > 2 weeks
Motile trophozoites or cysts
Able to diagnose infection readily in acute illness
More difficult to diagnose in chronic or asymptomatic infection
Giardia lamblia
Viral 
Helicobacter pylori
Bacterial
Balantidium coli
Campylobacter
Clostridium difficile
Shigella