The North Carolina Experience with Mucopolysaccharidosis Type I Newborn Screening.

OBJECTIVE: To evaluate the performance of a 2-tiered newborn screening method for mucopolysaccharidosis type I (MPS I) in North Carolina. STUDY DESIGN: The screening algorithm included a flow injection analysis-tandem mass spectrometry assay as a first-tier screening method to measure α-L-iduronidase (IDUA) enzyme activity and Sanger sequencing of the IDUA gene on dried blood spots as a second-tier assay. The screening algorithm was revised to incorporate the Collaborative Laboratory Integrated Reports, an analytical interpretive tool, to reduce the false-positive rate. A medical history, physical examination, IDUA activity, and urinary glycosaminoglycan (GAG) analysis were obtained on all screen-positive infants. RESULTS: A total of 62 734 specimens were screened with 54 screen-positive samples using a cut-off of 15% of daily mean IDUA activity. The implementation of Collaborative Laboratory Integrated Reports reduced the number of specimens that screened positive to 19 infants. Of the infants identified as screen-positive, 1 had elevated urinary GAGs and a homozygous pathogenic variant associated with the severe form of MPS I. All other screen-positive infants had normal urinary GAG analysis; 13 newborns had pseudodeficiency alleles, 3 newborns had variants of unknown significance, and 2 had heterozygous pathogenic variants. CONCLUSIONS: An infant with severe MPS I was identified and referred for a hematopoietic stem cell transplant. Newborn IDUA enzyme deficiency is common in North Carolina, but most are due to pseudodeficiency alleles in infants with normal urinary GAG analysis and no evidence of disease. The pilot study confirmed the need for second-tier testing to reduce the follow-up burden.

An Age-Based Framework for Evaluating Genome-Scale Sequencing Results in Newborn Screening.

OBJECTIVE: To assess the performance of a standardized, age-based metric for scoring clinical actionability to evaluate conditions for inclusion in newborn screening and compare it with the results from other contemporary methods. STUDY DESIGN: The North Carolina Newborn Exome Sequencing for Universal Screening study developed an age-based, semiquantitative metric to assess the clinical actionability of gene-disease pairs and classify them with respect to age of onset or timing of interventions. This categorization was compared with the gold standard Recommended Uniform Screening Panel and other methods to evaluate gene-disease pairs for newborn genomic sequencing. RESULTS: We assessed 822 gene-disease pairs, enriched for pediatric onset of disease and suspected actionability. Of these, 466 were classified as having childhood onset and high actionability, analogous to conditions selected for the Recommended Uniform Screening Panel core panel. Another 245 were classified as having childhood onset and low to no actionability, 25 were classified as having adult onset and high actionability, 19 were classified as having adult onset and low to no actionability, and 67 were excluded due to controversial evidence and/or prenatal onset. CONCLUSIONS: This study describes a novel method to facilitate decisions about the potential use of genomic sequencing for newborn screening. These categories may assist parents and physicians in making informed decisions about the disclosure of results from voluntary genomic sequencing in children.