What is the preferred method for testing HIV infection in infants born to HIV-positive mothers?

The preferred method for testing HIV infection in infants born to HIV-positive mothers is the Polymerase Chain Reaction (PCR). This testing method is particularly valuable because it can detect the presence of the virus's genetic material (RNA or DNA) rather than the antibodies that the infant may not have developed yet. Infants may carry maternal antibodies for several months after birth, which can complicate the interpretation of serological tests like ELISA or Western blot.

PCR can confirm whether the infant is actually infected with HIV, making it indispensable for early diagnosis. This prompt diagnosis is crucial, as it allows for timely initiation of antiretroviral therapy, which can greatly improve health outcomes. Viral culture, while also an option, is less commonly used due to its higher complexity, longer turnaround time, and lower sensitivity compared to PCR in younger patients.

In summary, the choice of PCR for testing infants is due to its ability to directly identify the virus irrespective of maternal antibody presence, making it the most reliable method for diagnosing HIV in this vulnerable population.