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
What is the best method to diagnose HIV in an infants? 
Select and explain. 
A. Western Blot, B. ELISA, C. PCR, D. All of the  above
C: PCR
Answer: C: PCR 
Explanation: In children younger then 18 months of age, WHO recommended HIV DNA or RNA PCR to diagnose HIV infection, as maternal antibodies may interface with antibody detetion.
In children > 18 months of age, demonstration of IgG antibody of HIV by ELISA and western blot establishes HIV infection.