This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
[{'content': 'In an infant born to a HIV infected mother, at what age of child the ELISA test can reliably diagnose HIV infection \nSelect and explain. \nA. 18 months, B. 9 months, C. 12 months, D. 3 months', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Enzyme-linked immunosorbent assay (ELISA) and Western blotting are used to initially detect HIV-specific antibodies but these tests are not used for diagnosis in patients younger than 18 months of age. This is because of the persistence of the maternal HIV antibody in infants younger than 18 months. \nInfants younger than 18 months require virologic assays that directly detect HIV in order to diagnose HIV infection.', 'role': 'assistant'}]