A cell-kinetic model of CD34+cell mobilization and harvest: development ofa predictive algorithm for CD34+cell yield in PBPC collections

BACKGROUND: Mobilization and homing of PBPCs are still poorly understood. T hus, a sufficient algorithm for the prediction of PBPC yield in apheresis p rocedures does not yet exist. STUDY DESIGN AND METHODS: The decline of CD34+ cells in the peripheral bloo d during apheresis and their simultaneous increase in the collection bag we re determined in a prospective study of 18 consecutive apheresis procedures . A cell-kinetic, four-compartment model describing these changes was devel oped. Retrospective data from 136 apheresis procedures served to further im prove this model. A predictive algorithm for the yield was developed that c onsidered the sex, weight, and height of the patient, the number of CD34+ c ells in peripheral blood before apheresis, the inlet flow, and the duration of the apheresis. The accuracy of this algorithm was evaluated by comparis on of the predicted and the observed yields of CD34+ cells in 105 prospecti ve autologous and 148 retrospective allogeneic apheresis procedures. RESULTS: The correlation between predicted and observed yields was good for the autologous and allogeneic groups with a correlation coefficient (r) of 0.8979 and 0.8311 (p<0.0001), respectively. The regression is described by the equations log (measured value [m]) = 1.0118 + 0.8595 x log (predicted value [p]) for the autologous and log (m) = 2.226 + 0.7559 x log (p) for th e allogeneic group. The respective equations for the zero-point regression are log (m)= 1.014 x log (p) and log (m) = 1.026 x log (p). The probability that the measured value was 90 percent or more of the predicted value was 83.8 percent for the autologous and 90.5 percent for the allogeneic apheres is procedures. CONCLUSION: The predictive accuracy of the algorithm and the slope of the z ero-point regression curve were higher for allogeneic than autologous PBPC collections. The predictive algorithm may be a useful tool in PBPC harvest, enabling the adaptation of the size of the apheresis to the needs of each patient.