Severe Combined Immunodeficiency (SCID) leads to life-threating infections unless the immune system can be restored through a transplant, enzyme replacement or gene therapy. Early detection of SCID through screening of all newborns can make possible life-saving intervention before infections occur.
Newborn Screening for SCID is currently only done in five provinces in Canada: Ontario (since 2014), Nova Scotia, New Brunswick and PEI (2016), and most recently Alberta in May (2019). CIPO continues to work with our National and Provincial partners to advocate for Newborn Screening for SCID across Canada.
Population based newborn screening happens on a large scale, a blood spot from a newborn heel is dried and used to test for a multitude of diseases that vary in every province.
T-cells are approximately 70% of lymphocytes in healthy infants, and the absence of T-cells causes the total lymphocyte count of most infants with SCID to be low. However, T-cells alone would not capture all SCID patients.
Therefore, the TREC test was developed. TREC (T-cell Receptor Excision Circles) are circular DNA molecules formed within the T-cells developing in the thymus. Normal infants have 1 TREC per 10 T-cells. Infants with SCID, lack TREC altogether.
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).