Routing improvement in the expanded neonatal screening system for primary immunodeficiencies diagnosis

Expanded neonatal screening (ENS) system is a crucial invention that was aimed at reducing infant mortality by enabling the early detection and treatment of severe and life-threatening conditions. Since its Russia-wide implementation in 2023 ENS had successfully identified hundreds of cases of newborns at risk allowing further timely medical intervention that often happened even at a pre-symptomatic stage. However, further optimization of patient routing algorithms within ENS is necessary in order to enhance the identification of newborns at risk and expedite their diagnosis and treatment. This manuscript focuses on optimizing of the routing algorithms specifically for newborns with suspected adenosine deaminase (ADA) deficiency, a severe form of primary immunodeficiency. Given the unique therapeutic and preventive measures required for these patients, the proposed guidelines expand the criteria for referring newborns for confirmatory diagnostics based on nucleoside metabolism data obtained from tandem mass spectrometry of dried blood spots. These improvements are aimed to the earliest detection and targeted treatment of newborns with ADA deficiency thereby enhancing the overall efficiency of primary immunodeficiency screening in Russia.