Key Messages
What Is Newborn Screening?
Newborn screening is a population-level public health intervention that involves testing done shortly after birth to check for serious and rare conditions during an early or asymptomatic stage. The goal of newborn screening is to enable earlier detection of serious and rare conditions to facilitate early treatment that may lead to improved health outcomes in newborns and young children. In Canada, newborn screening activities are within the scope of the provincial and territorial governments, as they provide health service delivery for their residents.
What Is the Purpose of This Recommendation and Evidence Review?
In support of the Government of Canada’s National Strategy for Drugs for Rare Diseases, Canada’s Drug Agency (CDA-AMC) convened the Newborn Screening Advisory Panel to develop pan-Canadian guidance and recommendations, which were published in March 2025. As part of their guidance, the Newborn Screening Advisory Panel recommended that a pilot evidence review be undertaken in the short term (i.e., 1 to 2 years) to inform recommendations concerning whether to add a condition to the Recommended Pan-Canadian Newborn Screening List.
The Newborn Screening Advisory Panel recommends 6 guiding principles as a core set of values to guide work related to newborn screening in Canada: the health rights of the newborn; equity; effectiveness, safety, and quality; transparency; collaboration; and sustainability. The Newborn Screening Advisory Panel considered the health rights of the newborn to be an overarching principle. Ethical justification for newborn screening rests on the expectation that all newborns who are screened can reasonably access timely, effective, and publicly funded diagnosis, treatment, and follow-up interventions and services, when appropriate, within the health system in which screening is offered.
What Is Metachromatic Leukodystrophy?
Metachromatic leukodystrophy (MLD) is a rare inherited condition that causes nerve damage. Depending on an individual’s age at the time of symptom development, metachromatic leukodystrophy is broadly classified as either early-onset or late-onset.
In its early-onset forms (i.e., late infantile and early juvenile), MLD progresses rapidly, causes substantial disability, and results in premature mortality. Children with early-onset MLD are rarely identified before symptom development. This can result in a long journey to receive a diagnosis and can limit timely access to supportive care or, where available, effective treatment. Identifying affected individuals before symptoms develop may provide benefit by offering timely access to available treatment.
Late-onset MLD (i.e., late juvenile and adult) often involves a slower progression that occurs over the course of years and can result in significant morbidity and premature mortality.
MLD was identified as an emerging condition of relevance for newborn screening in Canada in consultation with key experts from the newborn screening community in Canada and the Newborn Screening Advisory Panel. The recent development of a potential disease-modifying gene therapy for early-onset MLD has led jurisdictions to consider the addition of MLD to newborn screening programs internationally. This gene therapy has not yet been submitted for regulatory approval in Canada. MLD is not currently screened for in any jurisdiction in Canada as part of newborn screening programs.
How Did CDA-AMC Evaluate Newborn Screening for MLD?
CDA-AMC conducted an evidence review on the benefits and harms of newborn screening for MLD by considering the Newborn Screening Advisory Panel’s guidance and recommendations, reviewing the literature, and considering evidence from a wide range of sources, including input from experts, patient organizations, and interested parties. The evidence review informed deliberations by the Health Technology Expert Review Panel (HTERP) to make recommendations as to whether MLD should be added to the Recommended Pan-Canadian Newborn Screening List.