Background and Aims

Since January 1, 2019 levels of T cell receptor and kappa-deleting recombination excision circles (TREC, KREC) are measured as a part of the Swiss newborn screening program. We present findings of these first three years and compare outcomes of SCID patients to a historical cohort.

Methods

In all newborns with abnormal first screening, data on their medical history, laboratory findings and management were recorded in a centralised database.

Results

In total, 340 patients had abnormal findings on screening (0.13% of all tested newborns).

Eleven patients (3%) had severe immunodeficiency: eight had severe combined immunodeficiency (SCID, 2.7/year) and three had agammaglobulinemia. Furthermore, 36 patients (11%) had less severe immunodeficiencies. Seven SCID patients (88%) underwent hematopoietic stem cell transplantation at a median age of 4.5 months. One patient (12%) died of a viral infection after transplantation. Compared to a historical cohort of 15 SCID patients diagnosed over a period of 12 years (1.3/year), age at diagnosis and transplantation, mortality (33% vs 12%) and morbidity were lower in SCID patients identified by newborn screening.

In 251 patients (74%), abnormal screening results were transient and likely due to a variety of factors including prematurity, maternal immunosuppression, asphyxia, and trisomy 21.

Conclusions

The first three years of the Swiss newborn screening program have helped to identify a substantial number of children with severe immunodeficiencies. The number of patients diagnosed per year exceeds that of the previous 12 years by more than two times, suggesting that some children died before the introduction of screening without being diagnosed.