Development of a routine newborn screening protocol for severe combined immunodeficiency.
BACKGROUND
Severe combined immunodeficiency (SCID) is characterized by the absence of functional T cells and B cells. Without early diagnosis and treatment, infants with SCID die from severe infections within the first year of life.


OBJECTIVE
To determined the feasibility of detecting SCID in newborns by quantitating T-cell receptor excision circles (TRECs) from dried blood spots (DBSs) on newborn screening (NBS) cards.


METHODS
DNA was extracted from DBSs on deidentified NBS cards, and real-time quantitative PCR (RT-qPCR) was used to determine the number of TRECs. Positive controls consisted of DBS from a 1-week-old T(-)B(-)NK(+) patient with SCID and whole blood specimens selectively depleted of naive T cells.


RESULTS
The mean and median numbers of TRECs from 5766 deidentified DBSs were 827 and 708, respectively, per 3.2-mm punch ( approximately 3 muL whole blood). Ten samples failed to amplify TRECs on initial analysis; all but 1 demonstrated normal TRECs and beta-actin amplification on retesting. No TRECs were detected in either the SCID or naive T-cell-depleted samples, despite the presence of normal levels of beta-actin.


CONCLUSIONS
The use of RT-qPCR to quantitate TRECs from DNA extracted from newborn DBSs is a highly sensitive and specific screening test for SCID. This assay is currently being used in Wisconsin for routine screening infants for SCID.
Baker
Mei W
MW
Wisconsin State Laboratory of Hygiene, University of Wisconsin School of Medicine and Public Health, Madison, Wis 53706, USA. mwbaker@wisc.edu
Grossman
William J
WJ
Laessig
Ronald H
RH
Hoffman
Gary L
GL
Brokopp
Charles D
CD
Kurtycz
Daniel F
DF
Cogley
Michael F
MF
Litsheim
Thomas J
TJ
Katcher
Murray L
ML
Routes
John M
JM
D000199:Actins / Q000032:analysis / Q000276:immunology; D004247:DNA / Q000097:blood / Q000235:genetics; D006801:Humans; D007231:Infant, Newborn; D015997:Neonatal Screening / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods; D011948:Receptors, Antigen, T-Cell / Q000235:genetics* / Q000276:immunology; D015203:Reproducibility of Results; D016511:Severe Combined Immunodeficiency / Q000175:diagnosis* / Q000276:immunology
D000199:Actins; D011948:Receptors, Antigen, T-Cell; D004247:DNA