Statistics
We used Pearson’s χ2 qualitative test or Fisher’s exact test to analyze the association of lymphocyte recovery with the following categorical independent variables: gender, age group (≥ and <8 years), disease type (malignant, non-malignant), disease phase (early, advanced), donor type (MSD, haploidentical, unrelated), ABO compatibility (compatible, incompatible), stem cell source (peripheral blood stem cells [PBSC], bone marrow [BM]), conditioning regimen (myeloablative conditioning [MAC], reduced-intensity conditioning [RIC]), and use of serotherapy (yes, no). Mann-Whitney U test was used to assess the association of lymphocyte recovery with the dose of total nucleated cells (TNC) and CD34+ infused, and Kruskal-Wallis test to compare lymphocyte counts according to the donor.
Time-dependent variables were calculated from the date of the HSCT to the event. Respective cumulative incidences (CI) were estimated using Gray’s method, accounting for competing risks. Death without an event was considered a competing risk for all variables, however, for aGvHD graft failure was also included. To evaluate the effect of significant variables on such outcomes we performed Fine-Gray competing risks univariate and multivariate regression. Overall survival (OS) was analyzed using the Kaplan-Meier method and differences between groups were estimated using log-rank test. Univariate and multivariate Cox regression models were used to assess the impact of the significant variables. Only significant variables in univariate analyses were included in multivariate models. Due to the small sample size, it was not possible to evaluate subgroups of immune recovery for outcomes. AllP -values <0.05 were considered statistically significant. Statistical analyses were performed using SPSS version 25.0 (SPSS Inc., Chicago, IL, USA), and EZR version 1.40 (Saitama Medical Center, Jichi Medical University, Japan).