Newborn Screening for Spinal Muscular Atrophy: Ontario Testing and Follow-up Recommendations


Background:Spinal muscular atrophy (SMA) is characterized by the progressive loss of motor neurons causing muscle atrophy and weakness. Nusinersen, the first effective SMA therapy was approved by Health Canada in June 2017 and has been added to the provincial formulary of all but one Canadian province. Access to this effective therapy has triggered the inclusion of SMA in an increasing number of Newborn Screening (NBS) programs. However, the range of disease-modifying SMN2 gene copy numbers encountered in survival motor neuron 1 (SMN1)-null individuals means that neither screen-positive definition nor resulting treatment decisions can be determined by SMN1 genotype alone. We outline an approach to this challenge, one that specifically addresses the case of SMA newborns with four copies of SMN2.

Objectives:To develop a standardized post-referral evaluation pathway for babies with a positive SMA NBS screen result.

Methods:An SMA NBS pilot trial in Ontario using first-tier MassARRAY and second-tier multi-ligand probe amplification (MLPA) was launched in January 2020. Prior to this, Ontario pediatric neuromuscular disease and NBS experts met to review the evidence regarding the diagnosis and treatment of children with SMA as it pertained to NBS. A post-referral evaluation algorithm was developed, outlining timelines for patient retrieval and management.

Conclusions:Ontario’s pilot NBS program has created a standardized path to facilitate early diagnosis of SMA and initiation of treatment. The goal is to provide timely access to those SMA infants in need of therapy to optimize motor function and prolong survival.

Lead Researchers

Link to Publication


  1. Hugh McMillan

    Investigator, CHEO Research Institute

    View Profile Email
  2. Alex MacKenzie

    Senior Scientist, CHEO Research Institute

    View Profile Email
  3. Pranesh Chakraborty

    Investigator, CHEO Research Institute

    View Profile Email