History of Newborn Screening
Phenylketonuria (PKU) is a genetic disorder that can be caused by a deficiency of phenylalanine hydroxylase. Delay in treatment results in neurologic damage. Before newborn screening became available, PKU was typically not diagnosed before six months of life, when developmental delay or other nonspecific neurological symptoms become apparent. Treatment based on a phenylalanine-restricted diet was identified in the 1950s. While dietary treatment can prevent damage, already incurred neurologic damage can not be reversed. To allow presymptomatic identification of PKU patients and timely initiation of dietary intervention, a simple method for measuring phenylalanine in dried blood spots (on filter paper) was developed by Dr. Robert Guthrie. Once this bacterial inhibition assay was established, newborn screening began in some regions of New England in 1961 and rapidly spread around the world as the Guthrie Test.
Additional disorders such as congenital hypothyroidism, galactosemia, and sickle cell disease were soon added to many newborn screening programs. In the early 1990s, the introduction of MS/MS enabled an expansion of newborn screening programs to include more than 30 disorders. However, because screening is at the discretion of each state, significant discrepancy exists between states, with some states testing for as few as 3 disorders, while others test for more than 40. While individually rare, the incidence for any of the detectable disorders is 1 in 4,000 newborns, with Medium-Chain Acyl-Coenzyme A Dehydrogenase (MCAD) deficiency being more frequent than PKU at 1 in 12,000 vs. 1 in 20,000 newborns, respectively.