Please identify and explain the procedure for PKU testing on newborns in detail.
A Phenylketonuria (PKU) screening test is given to all newborns in the United States and Canada to make sure the enzyme necessary to process phenylalanine, an amino acid needed for normal development, is present. The actual PKU test consists of a simple heel stick to obtain a blood sample. Once the heel is poked with a small needle, a few drops of blood are collected on a special piece of paper. Only about 250 babies are diagnosed with PKU on average per year in the United States. It is an inherited disorder and is more common in Caucasian and Native American populations. If a newborn lacks the enzyme that converts phenylalanine into tyrosine, the phenylalanine will build up in the baby's blood causing serious, irreparable brain damage.