Newborn screening for PKU was initiated in 1963, and by the 1970s had become standard practice throughout the United States (Ross, 2010). Over the next decades, other con- galactosemia, ons such as hypothyroidism, and biotinidase deficiency hemoglobinopathies, are added to NBS panels. The total number of conditions scanned for remained relatively low constraints and guidelines due to technological that required the condition to be well character- ized and efficacious treatments readily available Wilson & Jungner, 1968).