Newborn screening (NBS) for Severe Combined Immunodeficiency (SCID) has been successfully implemented in all 50 United States and Puerto Rico from 2008-2018. This life-saving tool drastically improved overall survival of babies diagnosed with SCID 74% to 96%. TREC is a stable, circular DNA molecule that produced during the process T-cell receptor (TCR) rearrangement target quantitative PCR scre...