Spinal muscular atrophy (SMA) was added to the HHS Secretary’s Recommended Uniform Screening Panel for newborn screening (NBS) in 2018, enabling early diagnosis and treatment of impacted infants to prevent irreversible motor neuron damage. In anticipation of supporting SMA newborn screening, scientists at the U.S. Centers for Disease Control and Prevention (CDC) have worked towards building resources for public health laboratories in four phases since 2013. In Phase 1, CDC established a real-time PCR assay, which uses a locked nucleic acid probe to attain the needed specificity, to detect SMN1 exon 7. In Phase 2, we developed quality assurance dried blood spot materials made with transduced lymphoblast cell lines established from de-identified SMA patients, carriers, and unaffected donors. In 2021, CDC implemented Phase 3, a proficiency testing program, that now supports 115 NBS labs around the world. We are currently completing Phase 4, which includes the implementation of an external SMA quality control material program. Also, during this time, CDC has provided individual technical assistance to NBS programs and bench training to NBS scientists during our annual molecular workshop. These CDC-led activities have contributed to the rapid and full implementation of SMA screening in all 50 U.S. states as of February 2024.

Newborn bloodspot screening for one or more lysosomal storage disorders (NBS-LSD) is currently performed by many public health NBS laboratories globally. The screening tests measure activities of selected lysosomal enzymes on dried blood spot (DBS) specimens collected from newborns by the heel stick method Because these assays measure enzyme activity, the quantitative results are dependent on the particular analytical method. DBS quality control (DBS QC) materials with assay-specific certified values that span the relevant range from typical to LSD-affected newborns are an important component of quality assurance in NBS laboratories. The Newborn Screening Quality Assurance Program (NSQAP) at the U.S. Centers for Disease Control and Prevention (CDC) provides public health NBS laboratories with DBS QC sets for NBS-LSD comprising four admixtures of pooled umbilical cord blood and a base pool made from leukodepleted peripheral blood and heat-inactivated serum. To evaluate the suitability of these materials for use with digital microfluidics fluorometry (DMF) assays which can currently measure the activity of four enzymes (acid α-galactosidase (GLA); acid β-glucocerebrosidase (GBA); acid α-glucosidase (GAA); and iduronidase (IDUA)), CDC collaborated with the Newborn Screening Unit at the Missouri State Public Health Laboratory (MSPHL). Using MSPHL criteria, we found that the certified results from each of two DBS QC lots collectively spanned the range from typical (screen negative) to enzyme deficient (screen positive) newborn DBS levels for each of the four lysosomal enzymes measured. The range included borderline results that would require repeat screening of the newborn under the MSPHL protocol. We conclude that these DBS QC preparations are suitable for use as external quality control materials for DMF assays used to detect LSDs in newborns.

Screening for spinal muscular atrophy (SMA) was adopted by all US state newborn screening programs between 2018 and 2024; by the end of 2022, 48 states were screening for SMA. We assessed trends in health insurance records of SMA diagnoses to quantify improvements in the timeliness of SMA identification following the adoption of screening. We used nationally representative Medicaid claims data for approximately half of US births covered by public insurance and a convenience sample of employer-sponsored health plans. We analyzed records for birth cohorts with at least 1 full year of follow-up (i.e., through the end of the following calendar year). For 2017 births, 1.3 per 100,000 infants had SMA codes first recorded by 1 month of age; this increased to 6.6 per 100,000 among publicly insured newborns born in 2022. The rollout of SMA newborn screening across US states was also followed by improvements in the timely detection of SMA. The proportion of infants with SMA detected by 1 month increased from 18% in 2017 to 61% in 2021 and is projected to reach 75% in 2022. Growth in timely detection was even greater in the employer-insured sample. Timely diagnosis of SMA can enable the initiation of treatment prior to the irreversible loss of motor function.