Challenges of newborn severe combined immunodeficiency screening among premature infants.

Newborn screening for severe combined immunodeficiency (SCID) is currently being performed in many states. It is important to address diagnostic challenges while outcomes are emerging from the first several years of screening. We present the case of a premature infant whose initial newborn screen was strongly positive for SCID. Subsequent lymphocyte subset analysis by flow cytometry was difficult to interpret due to the lack of age-matched reference values, a history of prenatal corticosteroid administration, and the possibility of maternal or posttransfusion engraftment. A repeat newborn screen for SCID ultimately revealed a normal result, confirming the initial newborn screen as a false positive. This case report reveals several of the diagnostic challenges unique to newborn SCID screening in premature infants and highlights the potential for states to address the feasibility of a standard protocol in this population.