Initiation of newborn screening (NBS) programs in Europe dates back to the 1960s. One of the most recent expansions of NBS programs was the addition of severe combined immunodeficiency (SCID) based on detection of T-cell receptor excision circles (TRECs). In this review, we present an overview of the current situation in Europe. To avoid a biased overview based on only published results, a 37-item survey on TREC-based NBS was sent to representatives of 46 European countries. With a response rate of 83%, we collected data of 38 countries. Seventeen of the 38 European countries that have completed the survey have nationally or regionally implemented TREC-based NBS. The survey results emphasize similarities and differences as well as common practices and challenges in TREC-based NBS. Because TRECs are a general surrogate marker for severe T lymphocytopenia, conditions other than SCID are also identified. Therefore, the initial definition of the target disease as "SCID" might need to be reconsidered and extended to "SCID and severe T lymphocytopenia." Even though complete harmonization of TREC-based NBS programs across Europe will remain challenging, collaboration and close partnerships will help in the move toward universal TREC-based screening for all newborns, resulting in more infants with SCID and severe T lymphocytopenia being detected each year.

Center for Inherited Metabolic Diseases Karolinska University Hospital and Department of Molecular Medicine and Surgery Karolinska Institutet Stockholm Sweden

Department of Immunology 2nd Faculty of Medicine Charles University and Motol University Hospital Prague Czech Republic

Division of Immunology and the Children's Research Center University Children's Hospital Zurich University of Zurich Zurich Switzerland

Division of Pediatric Hematology and Oncology Department of Pediatric and Adolescent Medicine University Medical Center Freiburg University of Freiburg Freiburg Germany

Institute for Immunodeficiency Center for Chronic Immunodeficiency Faculty of Medicine Medical Center University of Freiburg Freiburg Germany

Laboratory for Paediatric Immunology Willem Alexander Children's Hospital Leiden University Medical Center Leiden The Netherlands

Norwegian National Unit for Newborn Screening Division of Pediatric and Adolescent Medicine Oslo University Hospital Rikshospitalet Oslo Norway

Pediatric Infectious Diseases and Immunodeficiencies Unit Children's Hospital Vall d'Hebron Barcelona Hospital Barcelona Spain

Translational and Clinical Research Institute Newcastle University and Paediatric Haematopoietic Stem Cell Transplant Unit Great North Children's Hospital Newcastle upon Tyne United Kingdom

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