Immature granulocyte fraction in the peripheral blood is a practical indicator for mobilization of CD34(+) cells.

We propose a simple parameter that improves prediction of the number of CD34(+) cells in blood cells collected by apheresis for autologous peripheral blood stem cell (PBSC) transplantation following administration of granulocyte colony-stimulating factor. The percentage of immature granulocytes including myeloblasts, promyelocytes, myelocytes, and metamyelocytes (LSI for left-shift index) immediately prior to the start of each apheresis correlated with the number of CD34(+) cells in PBSC collections (r = 0.79, P < 0.0001, Y = 0.227X - 0.99, R(2) = 0.623) much better than did the white blood cell count (r = 0.07), currently the most commonly used predictor in deciding the initiation of apheresis. We then used receiver operating characteristic (ROC) curves to determine a cutoff point for LSI to prevent unnecessary apheresis. At LSI > 7.5, sensitivity and specificity of cutoff points in the probability of obtaining >1.0 x 10(6) CD34(+) cells/kg BW were 93.3% and 94.3% (95% CI, 91.4-100.0%), respectively. When LSI reaches 15.25, nearly 100% of apheresis will attain the target CD34(+) cell dose. These findings indicate that LSI is a useful and simple method for predicting the yield of CD34(+) cells before the start of PBSC collection and avoiding unnecessary apheresis.