A new test developed at CHU Sainte-Justine in Montreal will enable better management of patients with severe combined immunodeficiency (SCID). The results of the study were presented in the medical journal Blood Advances published by the American Society of Hematology. Routine neonatal screening, although not yet available in Quebec, has led to an increase in the incidence of patients diagnosed with SCID in North America in recent years. This syndrome, a group of rare hereditary genetic disorders, is characterized by a total absence of immune system function, including an absence of T-lymphocytes, the white blood cells that play a crucial role in the body's immune defence. Without appropriate treatment, the disorder is fatal during the first months of life in the majority of cases. Many of the genes involved in SCID have been identified, but clinicians sometimes come across patients who do not have any identified genetic abnormalities.