CAUSES OF T-CELL LYMPHOPENIA IDENTIFIED ON NEWBORN SCREENING IN VIRGINIA 2015-2018: A SINGLE CENTER EXPERIENCE

Abstract

Introduction Virginia instituted newborn screening (NBS) for severe combined immunodeficiency (SCID) in June of 2015. The NBS uses a T-cell receptor excision circle (TREC) assay to evaluate for T-cell lymphopenia. The objective of this study was to identify underlying causes of T-cell lymphopenia in infants who have an abnormal screen but do not have confirmed SCID. Methods Retrospective chart review of patients with abnormal or critical TREC assays was performed. A screen was considered abnormal if the TREC cycle threshold was between 35.51 - 38.3, and critical if it was 0 or greater than 38.3. Results There were 78 patients evaluated with either an abnormal or critical initial or repeat NBS. Of those 78 patients, 11 had a normal initial NBS and subsequent abnormal repeats. These patients did not require further workup. Repeat NBS was normal for 27 patients who had an initial abnormal or critical screen. These patients did not require flow cytometry. Flow cytometry was performed for 40 patients with an abnormal or critical screen and it was normal in 30 patients. Of the 10 abnormal flow cytometry results, one patient had SCID. One patient had Jacobsen syndrome. Two patients had partial DiGeorge Syndrome. Lastly, there were 6 patients with idiopathic CD4+ lymphopenia. Conclusions Newborn screening for SCID is also able to identify non-SCID T-cell lymphopenia. It is important to recognize these patients to ensure necessary management and follow up. In addition, changes in screening guidelines may be needed to decrease the number of false positive results.