Presentation of Quiz #3

A patient is diagnosed as having diarrhea and 2 stool specimens are submitted to the laboratory. After examination of the concentration sediment from both specimens, nothing was seen and the results were reported as NO PARASITES SEEN. No permanent stained smears were prepared and/or examined. The patient continued to be symptomatic with GI problems and diarrhea. Would you agree or disagree with the original diagnostic approach? The patient submitted another stool specimen and both concentration sediment and permanent stained smears were examined. The parasites identified are seen below. If one considers all the intestinal protozoa, what organisms might have been missed without the permanent stained smear examination? What organism identification requires the permanent stained smear for identification? Why is this true? What references might be helpful in reviewing guidelines for a complete O&P examination?

These protozoan trophozoites measure approximately 13 to 16 ┬Ám long. The one on the left is stained with iron hematoxylin; the one on the right is stained with trichrome. Hint: They are flagellates. Note that both trophozoites contain two fragmented nuclei.

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The content within this site is made possible through the extensive contribution of Lynne S. Garcia, M.S., MT(ASCP), CLS(NCA), BLM(AAB), F(AAM), Director, Consultantation and Training Services (Diagnostic Medical Parasitology and Health Care Administration). For additional information, she can be contacted at

Reference: Garcia, L.S. 2015. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.