Which diagnostic method is correctly matched with Cryptosporidium in HIV patients?

• A. Blood culture
• B. Sputum smear
• C. Urine antigen test
• D. Stool antigen testing or modified acid-fast staining

Answer: (D)

The key idea is that Cryptosporidium infection in HIV patients is detected by looking for the parasite in stool, since it primarily affects the intestine and is shed in feces. Stool antigen tests detect Cryptosporidium-specific substances directly in stool, offering a quick and sensitive way to confirm infection. Microscopic detection with a modified acid-fast stain can also visualize the oocysts in stool samples, supporting the diagnosis. These methods target the site where the parasite lives and is excreted. Blood cultures won’t reveal Cryptosporidium because it’s not a blood-borne organism, sputum smears won’t capture intestinal oocysts, and urine antigen testing isn’t a standard or reliable method for this parasite. Therefore, stool antigen testing or modified acid-fast staining is the best match for diagnosing Cryptosporidium in HIV patients.