What is the role of newborn screening in the diagnosis of severe combined immunodeficiency (SCID)?

Updated: Apr 28, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD  more...
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SCID is under consideration for population-based newborn screening. [54] Screening tests do not prevent SCID but can identify infants early, before complications develop, thereby permitting earlier initiation of treatment. Diagnosis at birth may allow for better protection of babies with SCID from infection and improve transplantation outcome, significantly, improving the outcome in this otherwise potentially devastating condition. [55]

Newborn screening to identify SCID is currently performed in several American states using polymerase chain reaction (PCR) of DNA from universally collected, dried blood spots. [56]

Some states now screen all neonates for the most common forms of SCID by identifying T-cell receptor excision circles (TRECs). TRECs are a normal byproduct of T-cell receptor rearrangement. They can be detected in a newborn dried blood spot by using a unique molecular assay as a primary screen. In healthy neonates, they are made in large numbers, whereas in infants with SCID, they are barely detectable.

The pronounced deficiency of TRECs in patients with SCID makes identification of TRECs a reasonable screening test for the disease. Ideally, such screening will allow diagnosis and BMT before the infants become ill, thereby greatly increasing their chance of survival. [57, 58]

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