Newborn screening conditions: What we know, what we do not know, and how we will know it.

Expanding newborn screening beyond that for phenylketonuria was always the goal of Guthrie once phenylketonuria screening was on solid ground. He succeeded in this effort to an extent, adding screening for galactosemia, maple syrup urine disease, and homocystinuria. Screening for congenital hypothyroidism, congenital adrenal hyperplasia, biotinidase deficiency, and a few additional disorders was added by others over the years. However, a very large expansion of covered metabolic disorders eluded Guthrie despite his best efforts. This required a new screening technology, tandem mass spectrometry, which was not available until recently. Now, almost all developed newborn screening program use tandem mass spectrometry to cover the 29 metabolic disorders recommended for coverage by the American College of Medical Genetics and additional secondary disorders. The results have in some cases been spectacular in preventing or greatly reducing the burden of disease imposed by many of the screened disorders. However, expanded newborn screening has also brought problems that need to be addressed. These include lack of knowledge about the natural history of some of the disorders, absence of effective preventive therapy for others, identification of seemingly benign disorders or benign variants of severe disorders, and the resulting parental anxiety. To address these and other issues brought by expanded newborn screening, a national effort led by the American College of Medical Genetics has been developed. This effort known as the Newborn Screening Translational Research Network seeks to stimulate research, advocate pilot screening programs for proposed new additions to screening, and develop a protocol-based systematic long-term follow-up of infants identified in expanded screening programs. Upon the outcome, this critical effort will depend on the health and well-being of children throughout the United States.