The Wisconsin screening program uses a cutoff of 25 TRECs/mcL. Most screening programs have an algorithm in place for dealing with abnormal results. In Wisconsin, the first step is to redo the TREC assay. If the results are still positive, a physician member of the screening program is notified, who then contacts the newborn’s primary care physician. A decision is then made to either do another filter-paper specimen analysis or have a whole-blood specimen sent for T-cell enumeration by flow cytometry. A full workup for SCID is then recommended if results are still abnormal. (Curr. Opin. Pediatr. 2011;23:667-73).
In the first 18 months of the California screening program, 116 babies had samples sent for flow cytometry. Of those, 81 were normal. There were 10 cases of typical SCID, 1 child with Omenn syndrome (leaky SCID), 4 with variants of SCID, 8 with low T cell syndromes, and 7 with secondary causes of low T cells. There were 5 preterm births.
Children with leaky SCID may have a later onset of symptoms, with rash, adenopathy, and poorly functioning T cells. SCID variants include cartilage-hair hypoplasia, CHARGE syndrome (coloboma, heart defect, atresia choanae [also known as choanal atresia], retarded growth and development, genital abnormality, and ear abnormality), Down syndrome, or DiGeorge syndrome.
SCID newborn screening also could be helpful to children with non-SCID, secondary causes of T-cell lymphopenia who might also be vulnerable to serious opportunistic infections. Just recently, abnormal TREC findings led investigators to diagnose ataxia telangiectasia in two infants (J. Clin. Immunol. 2013;33:540-9).
Dr. Brower and Dr. Watson both said that they had no relevant financial disclosures.