Final answer:
The PKU test is conducted shortly after birth to screen for phenylketonuria, a metabolic disorder affecting 1 in 15,000 births. It helps in early identification and management through a strict low-phenylalanine diet. Timing can vary but generally within a few days of birth, once the newborn has consumed protein.
Step-by-step explanation:
The PKU test (phenylketonuria test) is a mandatory screening test for newborns. It is important because PKU affects around 1 in every 15,000 births in the United States. PKU is a condition where the individual lacks enough of an enzyme called phenylalanine hydroxylase, which is vital for breaking down the amino acid phenylalanine. High levels of phenylalanine can be toxic and lead to damage to the central nervous system and brain, with symptoms that can include delayed neurological development and intellectual disability, among others.
It is crucial that every infant be tested soon after birth because the earlier a modified diet is started, the less severe the symptoms are likely to be. An untreated person must follow a strict diet low in phenylalanine for life to prevent symptoms and damage to the brain. Phenylalanine is found at high levels in certain foods, such as artificial sweeteners and animal products, so intake of these must be monitored.
Regarding the timing of the test, it is generally recommended that the PKU test be performed within a few days of birth. However, the specific requirement can vary by hospital policy and state or country regulations. Typically, the test should be done after the newborn has ingested some protein to ensure accurate results, but before too much time has passed to start any necessary dietary interventions.