[Association between alterations in the expanded lymphoid profileby flow cytometry and inborn errors of immunity]

To evaluate the association between the expanded lymphoid profile and inborn errors of immunity using flow cytometry.

Observational and cross-sectional, case-control study, carried out in patients with a diagnosis or clinical suspicion of inborn errors of immunity, treated at the Santísima Trinidad Children's Hospital in Córdoba, Argentina, from August 2021 to November 2022. Clinical data were collected, and peripheral blood samples were obtained for flow cytometry analysis, using the PIDOT tube, to identify lymphocyte subpopulations. For statistical analysis, Fisher's exact test, odds ratio and binary logistic regression model were used.

40 cases and 20 controls were analyzed. The most frequently altered lymphocyte subpopulations were: CD4+ n (63%), Mem c/s (60%) and Mem s/s (55%). A statistically significant association was found between several lymphocyte subpopulations and health-disease status. Binary logistic regression reported Mem s/s and CD4+n as altered lymphocyte subpopulations with a greater probability to have inborn errors of immunity.

This study contributes to improving the understanding of inborn errors of immunity and demonstrates a strong association with altered lymphocyte subpopulation profiles. Mem s/s and CD4+n emerge as relevant biomarkers for diagnosis. Heterogeneity in different diseases and in flow cytometry underlines the importance of evaluating each patient individually, to improve diagnosis and treatment.