PKU screening is typically performed when?

• A. 1 to 3 days after birth
• B. At birth
• C. 2 weeks after birth
• D. At 6 months

Answer: (A)

Newborn screening for PKU is done so that any elevated phenylalanine can be detected early, allowing dietary treatment to prevent brain damage. The test uses a small heel-prick blood sample and is most reliable once feeding has begun and the baby’s metabolism is established. About one to three days after birth is ideal because it balances accuracy with the practical timing of hospital discharge; testing too early (at birth) can yield unreliable results, while waiting longer delays potential treatment. This window aligns with common screening practices, making it the best choice.