Stool antigen testing is used to detect which parasites?

• A. Giardia lamblia and Cryptosporidium parvum
• B. Entamoeba histolytica and Trichuris trichiura
• C. Taenia solium and Taenia saginata
• D. Plasmodium falciparum and Plasmodium vivax

Answer: (A)

Stool antigen testing uses immunoassays to detect parasite-specific proteins directly in the stool. The most common targets are Giardia lamblia and Cryptosporidium parvum because these organisms shed stable antigens that are readily captured by rapid tests, making diagnosis faster and often more sensitive than relying on microscopy alone. This approach is especially helpful for acute diarrheal illness when rapid results guide treatment and infection control.

Other choices involve organisms or detection methods not typically approached with standard stool antigen tests. For example, Taenia species are usually identified by eggs or proglottids in stool or via serology for certain cases; Plasmodium parasites are diagnosed from blood samples, not stool; and Trichuris trichiura is typically identified by eggs seen on stool microscopy.