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First Universal Newborn Screening Program for Severe Combined Immunodeficiency in Europe. Two-Years' Experience in
Ana Argudo-Ramírez1, Andrea Martín-Nalda2, Jose L Marín-Soria1
1Newborn Screening Laboratory, Inborn Errors of Metabolism Division, Biochemistry and Molecular Genetics Department, Hospital Clínic, Barcelona, Spain.
Insights
Newborn screening for Severe Combined Immunodeficiency (SCID) using T-cell receptor excision circles (TRECs) in Catalonia has demonstrated its effectiveness. Early detection through this method significantly improves patient outcomes and survival rates for this T-cell immunodeficiency.
Area of Science:
- Immunology
- Genetics
- Pediatrics
Background:
- Severe combined immunodeficiency (SCID) is a critical T-cell immunodeficiency diagnosed through newborn screening.
- Quantifying T-cell receptor excision circles (TRECs) in dried blood spot (DBS) samples enables early SCID detection.
- Catalonia initiated universal newborn screening for SCID in January 2017, becoming a pioneer in Spain and Europe.
Purpose of the Study:
- To evaluate the initial two years of newborn screening for SCID in Catalonia.
- To assess the incidence of SCID and other T-cell lymphopenias.
- To analyze the effectiveness of the TREC-based screening algorithm and its adjustments.
Main Methods:
- Screening of 130,903 newborns between January 2017 and December 2018 using TREC quantification in DBS samples.
- Utilized the Enlite Neonatal TREC kit for TREC measurement.
- Adjusted the retest cutoff from 34 to 24 copies/μL in 2018, followed by lymphocyte phenotyping and proliferation assays for positive cases.
Main Results:
- One case of SCID was diagnosed, yielding an incidence of 1 in 130,903 births.
- Thirteen patients (1 in 10,069 births) presented with clinically significant T-cell lymphopenia (non-SCID).
- The algorithm update reduced the retest rate from 3.34% to 1.4%, with a 0.02% positive detection rate.
Conclusions:
- Newborn screening for SCID using TREC quantification is effective in early detection and management.
- The program successfully identified SCID and T-cell lymphopenias, underscoring the benefits of universal screening.
- Further long-term follow-up is necessary to establish the precise incidence of SCID in Catalonia.
Abstract:
Severe combined immunodeficiency (SCID), the most severe form of T-cell immunodeficiency, can be screened at birth by quantifying T-cell receptor excision circles (TRECs) in dried blood spot (DBS) samples. Early detection of this condition speeds up the establishment of appropriate treatment and increases the patient's life expectancy. Newborn screening for SCID started in January 2017 in Catalonia, the first Spanish and European region to universally include this testing. The results obtained in the first 2 years of experience are evaluated here. All babies born between January 2017 and December 2018 were screened. TREC quantification in DBS (1.5 mm diameter) was performed with the Enlite Neonatal TREC kit from PerkinElmer (Turku, Finland). In 2018, the retest cutoff in the detection algorithm was updated based on the experience gained in the first year, and changed from 34 to 24 copies/μL. This decreased the retest rate from 3.34 to 1.4% (global retest rate, 2.4%), with a requested second sample rate of 0.23% and a positive detection rate of 0.02%. Lymphocyte phenotype (T, B, NK populations), expression of CD45RA/RO isoforms, percentage and intensity of TCR αβ and TCR γδ, presence of HLA-DR+ T lymphocytes, and in vitro lymphocyte proliferation were studied in all patients by flow cytometry. Of 130,903 newborns screened, 30 tested positive, 15 of which were male. During the study period, one patient was diagnosed with SCID: incidence, 1 in 130,903 births in Catalonia. Thirteen patients had clinically significant T-cell lymphopenia (non-SCID) with an incidence of 1 in 10,069 newborns (43% of positive detections). Nine patients were considered false-positive cases because of an initially normal lymphocyte count with normalization of TRECs between 3 and 6 months of life, four infants had transient lymphopenia due to an initially low lymphocyte count with recovery in the following months, and three patients are still under study. The results obtained provide further evidence of the benefits of including this disease in newborn screening programs. Longer follow-up is needed to define the exact incidence of SCID in Catalonia.
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