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

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 kappadeleting recombination excision circles (KREC) were measured simultaneously using a quantitative PCR-based method on DNA extracted from dried blood spots (DBS), with betaactin 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.Michela Barbaro, Annika Ohlsson and Stephan Borte contributed equally to this work.Electronic supplementary material The online version of this article

Newborn Screening for Primary Immune Deficiencies with a TREC/KREC/ACTB Triplex Assay—A Three-Year Pilot Study in Sweden

“…All normalized within 3-4 weeks after birth. Low TREC levels, because of immunosuppressive treatment, has been described before [21] but the B-cell synthesis is obviously more sensitive to these treatments, as reported earlier [13,19]. The future will tell if these infants will have any problems caused by this immune depression during fetal life.…”

“…The TREC/KREC assay was performed as described previously, [12,13]. Briefly, DNA was extracted from single 3.2 mm diameter punches of the DBS in 96 well plates.…”

“…In the first two years of the pilot study, samples from 58,834 newborns were analyzed [13]. In the third year, additional samples from 30,628 newborns are included (total 89,462 for the whole three-year study), Figure 1.…”

“…A triple assay combining TREC and KREC and β-actin (ACTB) as control was developed [12] for neonatal screening. This was employed in a pilot screening of newborn infants for PID, over the course of three years in the County of Stockholm and we have reported the results of the first two years previously [13]. In this paper, we summarize the results from the whole study period.…”

Newborn Screening for Severe Combined Immunodeficiency in Israel

“…Preterm neonates are more likely to produce false positive (FP) results [24]. As such, so long as a preterm infant is hospitalized, a new, repeat Guthrie card is tested every two weeks.…”