Age-matched lymphocyte subpopulation reference values in childhood and adolescence: application of exponential regression analysis

Background: Normal values of lymphocyte subpopulations for healthy children and adults have been published in defined age groups exclusively, which results in difficult data interpretation for patients close to the limit of contiguous age group ranges. In addition, normal values for a number of lymphocyte subpopulations have not been established to date. Objective: The aim of this study was to develop a model which provides continuous age-dependent reference values. This model was applied for lymphocyte subpopulations such as naive and memory T cells as well as their activation profile with diagnostic relevance in children and adults. Study design: A total of 100 blood samples, obtained from 80 healthy children and 20 adults were analysed by means of four colour-flow cytometry. Continuous age-dependent reference values were computed based on the residual values in an exponential regression model. Results: We calculated a continuous age-related regression model for both, absolute cell counts and percentages of CD3(+)CD4(+) T helper (T-H) cells, CD3(+)CD8(+) cytotoxic T cells, CD56(+)CD3(-) natural killer (NK) cells, CD56(+)CD3(+) T cells, CD3(+)CD4(+)CD45RA(+) naive T-H cells, CD3(+)CD4(+)CD45RO(+) memory T-H cells, CD3(+)CD8(+)CD45RA(+)CD28(+) naive cytotoxic T cells, CD3(+)CD8(+)CD45RO(+) memory cytotoxic T cells, CD3(+)CD8(+)CD69(+) early activated cytotoxic T cells and CD3(+)CD8(+)HLA-DR+ late activated cytotoxic T cells, respectively, to obtain reference values. Conclusion: Based on an exponential regression model, the obtained reference values reflect the continuous maturation of lymphocyte subsets during childhood.