Implementation of TREC/KREC detection protocol for newborn SCID screening in Bulgaria: a pilot study

Area of Science:

• Immunology
• Neonatal Medicine
• Genetics

Background:

• Inborn errors of immunity (IEI) require early diagnosis for improved patient outcomes.
• Neonatal screening using T-cell-receptor-excision circles (TRECs) and kappa-deleting recombination-excision circles (KRECs) from dried blood spots (DBS) is a promising diagnostic approach.
• Quantification of TRECs and KRECs allows for the assessment of T-cell and B-cell development, respectively.

Purpose of the Study:

• To evaluate the efficacy of a commercial kit for quantifying TRECs and KRECs in neonatal dried blood spots (DBS).
• To assess the correlation between TREC/KREC levels and lymphocyte subpopulations in infants with suspected or confirmed immune disorders.
• To determine the diagnostic accuracy of TREC/KREC assays for identifying severe combined immune deficiencies (SCID) and predicting B-cell abnormalities.

Main Methods:

• Quantification of TRECs and KRECs using a commercial kit on prospectively collected newborn Guthrie cards and DBS samples from patients with confirmed IEI.
• Retrospective flow cytometry analysis to evaluate the correspondence of TREC/KREC levels with lymphocyte subpopulations.
• Correlation analysis to assess the relationship between TREC/KREC levels and immune cell counts in patients with immune disorders.

Main Results:

• Testing of 2,228 Guthrie cards revealed low rates of TREC/KREC abnormalities (0.36% TREC positive, 1.05% KREC below cut-off), with a re-testing rate of 1.88%.
• The TREC/KREC assay demonstrated 100% accuracy in identifying severe combined immune deficiencies (SCID) when DBS were collected at birth.
• Significant correlations were observed between TREC levels and CD4+ T-cell counts (r=0.634) and total T-cell counts (r=0.536). KREC levels showed predictive ability for abnormal absolute and relative B-cell counts (AUCs 0.772 and 0.731, respectively).

Conclusions:

• Neonatal screening for IEI using TREC and KREC quantification from DBS is effective for early diagnosis.
• The TREC/KREC assay is highly sensitive for detecting SCID at birth.
• TREC and KREC levels correlate with T-cell and B-cell populations, respectively, aiding in the comprehensive assessment of immune status in newborns.