Cell dose and speed of engraftment in placental/umbilical cord blood transplantation: graft progenitor cell content is a better predictor than nucleated cell quantity.

There is evidence that the total cellular content of placental cord blood (PCB) grafts is related to the speed of engraftment, though the total nucleated cell (TNC) dose is not a precise predictor of the time of neutrophil or platelet engraftment. It is important to understand the reasons for the quantitative association and to improve the criteria for selecting PCB grafts by using indices more precisely predictive of engraftment. The posttransplant course of 204 patients who received grafts evaluated for hematopoietic colony-forming cell (CFC) content among 562 patients reported previously were analyzed using univariate and multivariate life-table techniques to determine whether CFC doses predicted hematopoietic engraftment speed and risk for transplant-related events more accurately than the TNC dose. Actuarial times to neutrophil and platelet engraftment were shown to correlate with the cell dose, whether estimated as TNC or CFC per kilogram of recipient's weight. CFC association with the day of recovery of 500 neutrophils/microL, measured as the coefficient of correlation, was stronger than that of the TNC (R = -0.46 and -0.413, respectively). In multivariate tests of speed of platelet and neutrophil engraftment and of probability of posttransplantation events, the inclusion of CFC in the model displaced the significance of the high relative risks associated with TNC. The CFC content of PCB units is associated more rigorously with the major covariates of posttransplantation survival than is the TNC and is, therefore, a better index of the hematopoietic content of PCB grafts. (Blood. 2000;96:2717-2722)