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.

Newborn screening for cystic fibrosis in Wisconsin: nine-year experience with routine trypsinogen/DNA testing.

OBJECTIVE: To describe the development and follow-up confirmatory results of the routine cystic fibrosis (CF) newborn screening (NBS) program in Wisconsin. METHODS: CF NBS has been performed on a routine clinical basis in Wisconsin since July 1994. The 2-tiered immunoreactive trypsinogen (IRT)/DNA technique was used on dried blood on filter paper spots. From July 1994 to February 2002, mutation analysis was for the DeltaF508 allele. Beginning in March 2002, multimutation analysis of 25 CF mutations was performed. Infants with a positive result on NBS were seen in certified CF centers for sweat testing by means of quantitative pilocarpine iontophoresis, and families received genetic counseling. RESULTS: From July 1994 to February 2002, there were 120 cases of CF detected by means of NBS (509,794 infants screened), with 53 DeltaF508 homozygotes and 67 compound heterozygotes. There were 8 clinically diagnosed cases of CF (no DeltaF508 allele). The CF incidence was 1:3983 (95%CI, 1:3373-1:4774). From March 2002 to June 2003, multimutation analysis identified 21 cases of classic CF (90,142 infants screened). Sweat tests were successfully performed in infants younger than 1 month. CONCLUSIONS: Early diagnosis of CF through NBS was successfully performed, with an estimated sensitivity rate of 99% using the IRT/25 CFTR multimutation assay.