Nationwide Implementation of Newborn Screening for Spinal Muscular Atrophy in Canada.

SMN1

Homozygous absence of SMN1 exon 7; SMN2 copy number as modifier and determinant of treatment access

This cross-sectional survey of laboratory directors of each provincial newborn screening programme, validated against public government sources, describes spinal muscular atrophy (SMA) screening in Canada and reports the first national birth prevalence. Between the start of screening (Ontario, January 2020; full national coverage in August 2024) and the end of 2025, 1,502,890 infants were screened and 120 had homozygous absence of SMN1 exon 7, a birth prevalence of 1 in 12,524 (95% CI 1:10,554 to 1:15,245). SMN2 copy number was 1 in 2 newborns (1.7%), 2 in 51 (42.5%), 3 in 41 (34.2%), 4 in 23 (19.2%) and 5 in 3 (2.5%). First- and second-tier methods, the timing of SMN2 copy number availability at first family contact, and reimbursement of disease-modifying therapies for infants with 4 copies vary between provinces.

Synthesis written by Geno'X. For the full original abstract, please refer to the source publication.

Useful figures for any SMA newborn screening programme, particularly the proportion of infants with 4 SMN2 copies (nearly one in five), a group for which the authors note growing expert consensus in favour of early treatment but unequal access. The message is organisational rather than genetic: universal screening does not guarantee equity if copy number reporting and reimbursement are not harmonised. Self-reported survey data, without clinical follow-up of screened infants.

Analysis by Dr Thibaut Benquey