Assessment of Platelet Activation and Immature Platelet Fraction as Predictors of Platelet Engraftment After Hematopoietic Stem Cell Transplantation

Delayed platelet engraftment is a well-known complication of umbilical cord blood transplantation (CBT). Megakaryocytes derived from cord blood (CB) in vitro are smaller than megakaryocytes derived from bone marrow (BM) in adults. A small megakaryocyte size might contribute to delayed megakaryocytic maturation. This study included 37 patients undergoing hematopoietic stem cell transplantation (HSCT) at Chang Gung Children's Hospital between July 2011 and June 2013. Blood samples were obtained at different times: preconditioning and post-HSCT days 56 and 97. To test whether platelet activation persists posttransplantation, two commonly used platelet activation marker antibodies, CD62P (P-selectin) and CD42b, were evaluated using whole blood flow cytometry, combining thiazole orange and anti-CD41a staining, to assess reticulated platelets. Serial peripheral blood (PB) samples were obtained posttransplantation from patients undergoing CBT (CBT group; n=15) and mobilized peripheral blood transplantation (PBT group; n=22). Platelet activation in the postengraftment samples was considerably higher in the PBT group than the CBT group. Moreover, immature platelet fractions (IPF) were higher in the CBT group. Our results emphasize the role of IPF for dynamic prediction of platelet engraftment in CBT.