Retrospective Analysis of a New York Newborn Screen Severe Combined Immunodeficiency Referral Center

In 2010, the New York State (NYS) Newborn Screen (NBS) Program added the T cell receptor excision circle (TREC) assay to screen for severe combined immunodeficiency disorder (SCID). The objective of this study was to perform a retrospective chart review of 199 infants referred to a single institution for abnormal TREC on NYS NBS between 2010 and 2017. Statistical analysis included analysis of variance, logistic regression models, chi-square, and linear mixed models. One hundred ninety-nine infants were found to have a TREC value of fewer than 200 copies/μL on NYS NBS. Infants were stratified as primary immunodeficiency (PID) (n = 54), immunocompetent (n = 133), lost to follow-up (n = 8), or deceased (n = 4). PID included SCID (n = 3), DiGeorge (n = 6), idiopathic lymphopenia (IL) (n = 44), and other syndromes associated with lymphopenia (n = 3). The 3 SCID cases were identified and brought to treatment, although all experienced significant infections. The study population was found to be predominately non-Hispanic, African American, and male. There was a difference in the average TREC values among those with immunocompetence (83 copies/μL), IL (81 copies/μL), and PID (40 copies/μL) (p < 0.05). On follow-up of 40 patients with IL, patients typically did not have severe infections during first few years of life. This study demonstrates that TREC value can be used to stratify infants for further confirmatory testing to exclude PID. Risk factors, such as stressful prenatal/postnatal conditions, prematurity, race, and sex may affect TREC value but cannot explain all causes of lymphopenia. This study may assist providers in risk stratifying the likelihood of PID with an abnormal TREC and determining the extent of the initial work up that is necessary at the time of a newborn's presentation.