Frequencies or Absolute Numbers? Cluster Analysis of Frequencies and Absolute Numbers of B-Cell Subsets in Dialysis Patients Who Are Candidates for Kidney Transplantation Reveals Different Profiles

<b>Background:</b> Detailed characterization of B cells in dialysis patients who are candidates for kidney transplant is still lacking, with little information on how dialysis duration and modality impact B cell subsets. <b>Methods:</b> Cluster analysis of flow cytometry determined the frequencies and absolute numbers of B-cell subsets and divided the cohort of 78 candidates into two distinct clusters, one with shorter and one with longer dialysis duration. <b>Results:</b> The immune profiles of the clusters differed depending on whether frequencies or absolute counts were considered. In long-term dialysis patients, the frequency of total memory, double negative and marginal zone B cells increased, while the frequency of naive and regulatory B cells decreased. This pattern was reversed in short-term dialysis patients, with a decrease in memory and an increase in naive and regulatory populations. The B subset number decreased significantly in long-term dialysis patients, while it increased significantly in short-term dialysis patients. The dialysis modality affected the frequency-based subset immune profiles. <b>Conclusions:</b> It is important to determine whether the evaluation is based on frequencies or absolute numbers. The different distribution of B cell subsets in the clusters, in terms of frequencies and absolute numbers, was influenced by dialysis duration. Modality and age only influenced the frequencies.