The impact of CD34+ cell dose on platelet engraftment in pediatric patients following unmanipulated haploidentical blood and marrow transplantation.

Objective: Unmanipulated haploidentical blood and marrow transplantation has been developed as an alternative transplant strategy for pediatric patients with hematological diseases. The aim of this study was to investigate the effects of donor and recipient characteristics on hematopoietic recovery in pediatric patients following unmanipulated haploidentical transplantation.
Methods: Factors correlating with hematopoietic recovery in 133 pediatric patients after unmanipulated haploidentical transplantation were analyzed retrospectively.
Results: All patients reached an absolute neutrophil count of 500/microl in a median of 12 days (range, 9-49 days). One hundred thirty-three patients reached an untransfused platelet count of more than 20,000/microl in a median of 15 days (range, 7-180 days). Univariate analysis showed five factors associated with platelet engraftment. These were time to transplantation after diagnosis (P = 0.072), infused nuclear cells/kg of recipient weight (P = 0.028), CD3+ cells/kg of recipient weight (P = 0.082), CD4+ cells/kg of recipient weight (P = 0.083), and CD34+ cells/kg of recipient weight (P = 0.012). Multivariate analysis showed that infused CD34+ cells/kg of recipient weight (CD34+ cells more than 2.42 x 10(6)/kg vs. less than or equal to 2.42 x 10(6)/kg, HR = 1.733; 95% CI 1.222-2.549; P = 0.002) were significantly associated with an increased risk of platelet engraftment. Patients receiving a CD34+ cell dose more than 2.42 x 10(6)/kg had a short time [12 days (range, 7-176 days)] to achieve an untransfused platelet engraftment, compared to 18 days (range, 7-180 days) in patients receiving a lower dose (P < 0.001).
Conclusions: Our results suggest that low number of CD34+ cells in allografts is a critical factor associated with delayed platelet engraftment after unmanipulated haploidentical transplantation in pediatric patients.