Reference Values for Extended Lymphocyte Subsets in Korean Children: A Multicenter Study Using the EuroFlow PIDOT...

Current reference intervals for lymphocyte subpopulations are primarily based on Western populations, with limited data available for Korean children, particularly for extended subsets. We determined absolute cell counts and percentages of lymphocyte subpopulations in Korean children, according to age and sex.

Samples from 92 children-stratified into two age groups, groups 1 (5-9 yrs) and 2 (10-17 yrs)-were obtained. Immunophenotyping was performed via flow cytometry using the Primary Immunodeficiency Orientation Tube (PIDOT) panel, primarily classifying the cells into T, B, and natural killer cell populations. T lymphocytes were divided into CD4⁺, CD8⁺, and CD4^-CD8^- subsets; T and B cells were further subdivided according to their maturation stage.

Children in group 1 exhibited higher absolute counts of total B cells, unswitched memory B cells/plasma cells, total T cells, CD4⁺ naïve cells, and TCRγδ⁺ T cells than those in group 2. In contrast, Group 2 children showed higher absolute counts of CD4⁺ effector memory (EM) T cells. Males had higher absolute counts of total B cells, particularly pregerminal center B cells, CD4⁺ EM cells, and CD8⁺ terminally differentiated T cells, whereas females showed higher proportions of CD4⁺, CD4⁺ naïve, and CD8⁺ central memory/transitional memory T cells.

To the best of our knowledge, this study is the first to establish reference values for extended lymphocyte subsets in Korean children using the PIDOT panel. Age, sex, and laboratory-related factors influenced lymphocyte subset distributions. These findings may serve as reference data for immune disorders and immunotherapy in pediatric populations.