What diagnostic test would confirm Entamoeba histolytica infection?

• A. Blood culture
• B. Urine antigen test
• C. Stool ova and parasites exam
• D. Colonoscopy with biopsy

Answer: (C)

Diagnosing Entamoeba histolytica infection is usually done by directly looking for the parasite in stool. The stool ova and parasites exam involves microscopic examination of a stool sample to detect cysts or trophozoites of the organism. Seeing trophozoites that contain ingested red blood cells is highly suggestive of E. histolytica and helps confirm infection; cysts may also be seen and support the diagnosis. This method is noninvasive and typically the first-line test for suspected intestinal amebiasis.

Blood cultures aren’t used for this protozoan infection, since it doesn’t circulate in blood in a way that those cultures would detect. A urine antigen test isn’t a standard test for Entamoeba histolytica. Colonoscopy with biopsy is more invasive and would be reserved for evaluating complications or unsure cases; it’s not the initial confirmatory test. In some scenarios, stool antigen tests or PCR can help differentiate E. histolytica from nonpathogenic Entamoeba species, but among the options given, the stool ova and parasites exam best confirms the infection.