Test reliably detects inherited immune deficiency in newborns

Aug. 22, 2014

A newborn screening test for severe combined immunodeficiency (SCID) reliably identifies infants with this life-threatening inherited condition, leading to prompt treatment and high survival rates, according to a study supported by the National Institutes of Health (NIH). The research, led by Jennifer Puck, MD, was published recently in the Journal of the American Medical Association.

The SCID newborn screening test, originally developed at the NIH, measures T-cell receptor excision circles (TRECs), a byproduct of T-cell development. Infants with SCID have few or no T cells, regardless of the underlying genetic defect, and the absence of TRECs may indicate SCID.

SCID was added in 2010 to the U.S. Department of Health and Human Services Recommended Uniform Screening Panel for newborns in the United States. Nearly half of states conduct newborn screening for SCID, and the test is performed for almost two-thirds of infants born across the country.

The current study evaluated data from more than three million newborns gathered by screening programs in 10 states. Overall, screening detected 52 newborns with SCID, equivalent to one in 58,000 infants. All infants with abnormal TREC results underwent further diagnostic testing to confirm SCID. The researchers did not identify any cases of SCID that were missed by TREC screening.

Use of the screening test revealed a different distribution of genetic defects underlying SCID than what has been previously estimated. For example, X-linked SCID, a form of the disorder caused by mutations in a gene on the X chromosome, previously had been thought to account for half of SCID cases, but researchers found that only 19% of newborn-screened SCID infants had X-linked disease. The proportion of SCID infants without a known genetic defect (15%) was higher than anticipated, indicating that widespread screening presents opportunities to discover previously unknown genes implicated in SCID. Read the study abstract.

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