Newborn Screening for Severe Primary Immunodeficiency Diseases in Sweden\u2014a 2-Year Pilot TREC and KREC Screening Study

Michela Barbaro,Ulrika Von Döbeln,Annika Ohlsson,Jovanka King,Susanne Jonsson,Jacek Winiarski,Stephan Borte,Rolf H Zetterström,Lennart Hammarström

doi:10.1007/s10875-016-0347-5

Abstract

Newborn screening for severe primary immunodeficiencies (PID), characterized by T and/or B cell lymphopenia, was carried out in a pilot program in the Stockholm County, Sweden, over a 2-year period, encompassing 58,834 children. T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) were measured simultaneously using a quantitative PCR-based method on DNA extracted from dried blood spots (DBS), with beta-actin serving as a quality control for DNA quantity. Diagnostic cutoff levels enabling identification of newborns with milder and reversible T and/or B cell lymphopenia were also evaluated. Sixty-four children were recalled for follow-up due to low TREC and/or KREC levels, and three patients with immunodeficiency (Artemis-SCID, ATM, and an as yet unclassified T cell lymphopenia/hypogammaglobulinemia) were identified. Of the positive samples, 24 were associated with prematurity. Thirteen children born to mothers treated with immunosuppressive agents during pregnancy (azathioprine (n = 9), mercaptopurine (n = 1), azathioprine and tacrolimus (n = 3)) showed low KREC levels at birth, which spontaneously normalized. Twenty-nine newborns had no apparent cause identified for their abnormal results, but normalized with time. Children with trisomy 21 (n = 43) showed a lower median number of both TREC (104 vs. 174 copies/μL blood) and KREC (45 vs. 100 copies/3.2 mm blood spot), but only one, born prematurely, fell below the cutoff level. Two children diagnosed with DiGeorge syndrome were found to have low TREC levels, but these were still above the cutoff level. This is the first large-scale screening study with a simultaneous detection of both TREC and KREC, allowing identification of newborns with both T and B cell defects.

Highlights

The purpose of neonatal screening is the early recognition of treatable, mostly genetically determined diseases that manifest with a high rate of morbidity and mortality
The vast majority recovered spontaneously (Supplementary Table 1) and the cutoff was subsequently lowered to a T cell receptor excision circles (TREC) level of 8 copies/3.2 mm blood spot or below and a kappadeleting recombination excision circles (KREC) level of 4 copies/3.2 mm blood spot blood or below
As these cutoffs were considered too stringent, they were changed to a TREC level of 10 copies/3.2 mm blood spot or below and a KREC level of 6 copies/3.2 mm blood spot or below

Summary

Introduction

The purpose of neonatal screening is the early recognition of treatable, mostly genetically determined diseases that manifest with a high rate of morbidity and mortality. Mass screening of newborn infants with dried blood spots (DBS) started in the early 1960s based on a method developed by Guthrie and Susi for diagnosing phenylketonuria [1]. The US congress decided in 2006 to include 29 core and 25 secondary disorders in its newborn screening program based on a priority list of disorders. A number of additional disorders, among them severe combined immunodeficiency (SCID), have been included in this list, based on the well-recognized Wilson and Jungner criteria [2]. In Sweden, neonatal screening with DBS was initiated in 1965 and today, a total of 24 disorders are included in the program

Methods

Results

Conclusion