Granulocyte collection efficiency and yield are enhanced by the use of a higher interface offset during apheresis of donors given granulocyte-colony-stimulating factor

BACKGROUND: Trials evaluating granulocyte transfusions for therapy of febrile neutropenia demonstrated mixed clinical results, which may in part be due to the low neutrophil cell dose of the transfused components. To optimize the latter variable, the effect of various interface offset (IO) settings during apheresis on granulocyte collection efficiency (GCE) and yield was determined in normal donors given granulocyte-colony-stimulating factor (G-CSF). STUDY DESIGN AND METHODS: Seventeen donors underwent 44 granulocyte collections performed with a continuous-flow blood cell separator with hetastarch infusion after stimulation with G-CSF (5 mu g/kg/day). Apheresis was performed alternatively using one of three IO settings: IO = 15 (Group 1, n = 16), IO = 25 (Group 2, n = 12), and IO = 35 (Group 3, n = 13).The GCE and yield and changes in donor platelet count, hematocrit (Hct), and red cell (RBC) volume of the components were compared among the three groups. RESULTS: The mean GCE was greater (p = 0.006) during apheresis at an IO setting of 35 (60 +/- 12%) than at an IO setting of 15(40 +/- 17%).The mean granulocyte yield (x10(10)) per procedure was 10.8 +/- 2.95 at an IO setting of 35 and 7.73 +/-4.02 at an IO setting of 15 (p = 0.08). In a multivariate linear regression model, factors independently associated with granulocyte yield were the absolute granulocyte count (r = 0.73, p<0.001) and blood volume of the donor (r = 0.54, p = 0.001) before the procedure and the use of an IO setting of 35 (r = 0.50, p = 0.002).There was no significant difference among the three groups in the decrement in donor platelet count or Hct with apheresis, although the mean RBC volume was greater in Group 3. CONCLUSION: Granulocyte apheresis at an IO setting of 35 rather than 15 resulted in a significant increase in the GCE.The use of an IO setting of 35 during apheresis was an independent factor associated with granulocyte yield in the multivariate model. Donor safety was not compromised by collecting granulocytes at the higher IO setting.