Newborn screening facilitates early theranostics and improved spinal muscular atrophy outcome: five-year real-world evidence from Taiwan.

Abstract

Background: Recent findings indicate that infants with spinal muscular atrophy (SMA) treated early through newborn screening (NBS) have better outcomes. This study aimed to investigate the long-term outcomes of a 5-year SMA NBS program in Taiwan.

Results: From September 2017 to August 2022, two NBS centers screened patients for SMN1 homozygous deletion using quantitative real-time polymerase chain reaction (RT-PCR) or the Sequenom MassARRAY platform and subsequently confirmed the findings using multiplex ligation-dependent probe amplification (MLPA). Implementation of SMA NBS using RT-PCR or MassARRAY platform efficiently led to the detection of neonates with homozygous survival motor neuron 1 (SMN1) deletions at a median age of 9 (range 4-14) days. Among the 446,966 newborns screened, 22 were detected to have a homozygous deletion of SMN1, followed by MLPA confirmation. One patient initially showed negative screening results but was later confirmed to have a compound heterozygous mutation. Among the 23 confirmed cases, 8 patients had two SMN2 copies (all classified as SMA type 1), 11 patients had three SMN2 copies (including 4 with SMA type 1, 2 with SMA type 2, 3 with SMA type 3, and 2 asymptomatic cases), and 4 patients had four SMN2 copies (all asymptomatic). The mean (median) follow-up duration for 19 survivors was 4.2 (5.0) years. All patients with two SMN2 copies developed symptoms within 62 days; those with three SMN2 copies experienced disease onset within 1 year. After diagnosis, most patients were on a watch and wait to receive disease-modifying therapy (DMT) due to initial lack of insurance coverage and limitations on indications after coverage was granted. Of the 19 children who received DMT, the outcomes included 12 walkers, 1 walker requiring support, 3 sitters, 1 non-sitter, and 2 patients with SMA type 1b with two SMN2 copies who succumbed to acute respiratory failure.

Conclusions: This 5-year SMA NBS study using RT-PCR or the MassARRAY platform, along with an extended follow-up, demonstrates that early diagnosis and prompt treatment can enhance SMA clinical outcomes and change its natural progression in the therapeutic era. Infants with NBS who received presymptomatic DMT had better clinical outcomes than those who received symptomatic DMT.