Table 3. Summary of California newborn screening with TRECs in the first year.

Over 500,000 births screened.

DNA amplification failures (DAF), <0.08%, requiring second heelstick.*

84% from neonatal intensive care units.

56% from infants who were <1500 g at birth.

44% had the failed sample obtained from an intravenous line.

50 infants had two DAF results or a positive result (0.01% of births), requiring CBC and lymphocyte analysis by flow cytometry.

20 of these (40%) had low T cells confirmed.

Diagnoses among infants with low T cells:

6 SCID**:

2 IL-7 recptor defects

2 RAG1 defects

2 Common γchain defects

1 Omenn syndrome*** with RAG2 defect

3 SCID variant with no known gene defect

4 Syndromes associated with T lymphocytopenia:

3 DiGeorge syndrome (1 complete)

1 Trisomy 21

6 Secondary T lymphocytopenia

2 Gastroschesis

1 Gastrointestinal atresia

3 Prematurity

^*Since all screening tests other than TRECs are performed in regional laboratories throughout California, with samples then forwarded to a central laboratory for TREC testing, most newborns were 2 weeks old when the TREC result was available. When a SCID-specific second heelstick was needed, older age usually resulted in a normal TREC value.

^**Only one SCID case had a positive family history leading to testing at birth.

^***Signs of Omenn syndrome in the first weeks of life had led to the diagnosis just before the TREC test was reported.