Immunopathology & Immunotherapy

September 30, 2014, marks the 50th anniversary of the Children’s Bureau recommendation for “the screening of all newborn infants for PKU [phenylketonuria] on a routine basis.”1 By 1968, 43 states had made screening for PKU mandatory.1 As a result of technological advances, newborn screening in the United States has been extended to as many as 37 core conditions in some states.2 As reported by Kwan and colleagues3 in this issue of JAMA, newborn screening for severe combined immunodeficiency (SCID) has been undertaken in 23 states and the Navajo Nation, beginning in Wisconsin in January 2008. The authors present data on more than 3 million newborns screened with a T-cell receptor excision circle (TREC) assay followed by confirmatory flow cytometry from 11 of these programs (10 states and the Navajo Nation).