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Newborn Screening for Severe Combined Immunodeficiency (SCID) in Canada

Population-based newborn screening happens on a large scale and can help detect health problems leading to faster and more effective treatment. The process involves a small prick to a baby’s heel and collecting a blood spot (similar to traditional diabetes testing). The blood spot is dried and used to test for a multitude of diseases that vary in each province.

What is SCID?

Severe Combined Immunodeficiency (SCID) makes a person highly susceptible to infection and is one of the most severe forms of primary immunodeficiency disease. SCID is fatal unless the immune system can be corrected or supported through a stem cell transplant, enzyme replacement or gene therapy.

Newborn screening allows early detection of SCID, dramatically improving the chances of successful treatment and life-saving interventions.

In Canada, SCID newborn screening is performed in the following provinces and territories:

  • Ontario (since 2014)
  • Nova Scotia (2016)
  • New Brunswick (2016)
  • PEI (2016)
  • Alberta (2019)
  • Manitoba (May 2020)
  • British Columbia (2022)
  • Yukon (2022)
  • Quebec (2023)

ImmUnity Canada continues to work with our National and Provincial partners to advocate for Newborn Screening for SCID across Canada.

T-cell Receptor Excision Circles (TREC) Testing

T-cells make up approximately 70% of healthy infants’ lymphocytes (white blood cells). In infants with SCID, the absence of T-cells causes the total lymphocyte count to be low. However, T-cells alone would not capture all SCID patients.

The TREC test helps identify at-risk infants before infection onset. TREC stands for T-cell Receptor Excision Circles, which are small circles of DNA created in T-cells as they pass through the thymus. Infants with a healthy-presenting immune system have one TREC per 10 T-cells. But infants with SCID don’t have any TREC.

Not all T-cell deficiency diseases are detected by the TREC test, as some deficiencies have patients born with normal TREC levels (NEMO, for example). But the field of immunology and our understanding of the immune system and genetics is growing quickly, so in time we may have more sophisticated testing and treatments for primary immunodeficiencies.


In 2020, ImmUnity Canada began working with immunologists and families in BC to advocate for SCID to be added to the existing BC provincial newborn screening program. With the help of members and partners, our campaign was successful. On October 12, 2022, the BC Ministry of Health announced the expansion of its newborn screening panel, including the addition of SCID. All babies born after September 30, 2022, in BC and Yukon are now screened for SCID in addition to 26 other treatable conditions.

We’re sick and tired, but we’re not alone.

ImmUnity Canada is a national charity with five provincial chapters across the country.

We empower Canadians impacted by immunodeficiency disorders to live well through education, support, advocacy, community-building, and research.

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