Abstract

5q spinal muscular atrophy (5q-SMA) is a leading genetic cause of infant mortality. Presymptomatic intervention with disease-modifying therapies significantly improves motor outcomes, but effectiveness depends on early detection through newborn screening (NBS). Despite global 5q-SMA NBS expansion and recent Brazilian federal legislation, regional disparities and a lack of systematic monitoring hinder access to timely diagnosis and care. This study addresses these gaps by evaluating a statewide pilot program in São Paulo. We used multiplex real-time PCR to detect SMN1 exon 7 deletions in dried blood spots, confirming SMN1/2 copy numbers via MLPA in positive cases. Under real-world conditions, timeliness key performance indicators were evaluated to assess operational efficiency. 194,714 newborns were screened with 14 positive cases, yielding a prevalence of 1:13,908. First-tier results and treatment initiation occurred at a median of 10.8 and 28 days of life, respectively. Notably, 78.6% of patients had two SMN2 copies, of which approximately half were symptomatic by the first evaluation, highlighting the critical need for rapid screening to prevent irreversible motor decline. Screening achieved 100% specificity. This pilot demonstrates the feasibility of 5q-SMA NBS within the Brazilian public health system, providing essential evidence to overcome logistical and socioeconomic barriers and support nationwide expansion.

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