Newborn screening for spinal muscular atrophy: The Wisconsin first year experience

Abstract

Spinal muscular atrophy was recently added to the Wisconsin newborn screening panel. Here we report our screening methods, algorithm, and outcomes. A multiplex real-time PCR assay was used to identify newborns with homozygous SMN1 exon 7 deletion, and those newborns' specimens further underwent a droplet digital PCR assay for SMN2 copy number assessment. An independent dried blood spot specimen was collected and tested to confirm the initial screening results for SMN1 and SMN2. From October 15, 2019 to October 14, 2020, a total of 60,984 newborns were screened for spinal muscular atrophy. Six newborns screened positive for and were confirmed to have spinal muscular atrophy, making the Wisconsin spinal muscular atrophy birth prevalence 1 in 10,164. Of these six infants, two have two copies of SMN2, two have three copies of SMN2, and two have four copies of SMN2. Five newborns received Zolgensma therapy, and one newborn received Spinraza therapy. Our screening method's positive predictive value is 100%. This comprehensive approach, providing both timely SMN2 information and SMN1 and SMN2 confirmation as parts of the algorithm for spinal muscular atrophy newborn screening, facilitated timely clinical follow-up, family counseling, and treatment planning.

Keywords: Droplet digital PCR, SMN1, and SMN2; Multiplex real-time PCR; Newborn screening; Spinal muscular atrophy.