Prospective Study of Early Neonatal Screening for Phenylketonuria

Abstract

Identification of phenylketonuria (PKU) in the newborn by routine screening depends on the presence of an increased concentration of phenylalanine in the blood when the specimen is obtained. In infants with PKU, phenylalanine is not substantially increased at birth.¹ It does, however, increase postnatally as a consequence of the infant's inability to metabolize the phenylalanine that is ingested or liberated from the breakdown of endogenous protein.In the United States, the initial blood specimen for PKU screening is obtained near the time of discharge from the nursery, which is usually on the third day of life. Because of the current . . .