PB2370 CD34+ CELL COUNT BY FLOW CYTOMETRY IS BETTER THAN HEMATOPOIETIC PROGENITOR CELL COUNT BY SYSMEX XN ANALYZERS IN SAMPLES COLLECTED PRE‐APHERESIS TO PREDICT APHERESIS PRODUCT STEM CELL YIELD

Background: In peripheral blood stem cell (PBSC) transplantation successful engraftment requires the infusion of enough CD34+ stem cells. CD34 cells are measured by flow cytometry. Sysmex XN analyzer counts hematopoietic progenitor cells (HPC) and is fast and inexpensive. Aims: We evaluated if the HPC count and CD34 cell count in samples collected from PB pre‐apheresis and from apheresis products during the apheresis could predict the apheresis product CD34+ cell yield. Methods: Apheresis was stopped once CD34+ cells ≥ 2 × 10 6 /kg in the apheresis product in autologous patients who will receive one transplant (Auto 1 group), ≥ 4 × 10 6 /kg in patients with mieloma diagnosis who will receive two transplants (Auto2 group) and ≥ 4 × 10 6 /kg in allogeneic transplants with healthy donors (Allo group). ROC curve was generated to visualize the sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) and the area under the curve (AUC) was measured. Positive HPC cut‐offs were calculated for predicting a CD34+ cell yield ≥ threshold with 100 % PPV and 100 % SP and negative HPC cut‐offs were calculated for predicting a CD34+ cell yield < threshold with 100% NPV and 100 % SE. Then we calculate correctly classified patients with the positive and negative HPC and CD34+ cell cut‐offs. Results: 80 consecutive patients were enrolled (50 Auto and 30 Allo). This study included the first apheresis for each patient (80 apheresis). Predictive value of HPC count and CD34+ cell count for apheresis product CD34+ cell yield. Samples collected pre‐apheresis. The AUC was 0.8264 and 0.8038 for HPC count in the Auto1 and Auto2 groups respectively. In table 1 we show positive and negative HPC cut‐offs to predict the target CD34+ cell yield. HPC count in pre‐apheresis samples could predict the target CD34+ cell yield in Auto group in 34.6 % of cases. In the same way we evaluated the predictive value of the pre‐apheresis CD34+ cell count. The AUC was 0.9881 and 0.900 in the Auto1 and Auto2 groups respectively. See positive and negative CD34+ cell cut‐offs in Table 1. CD34+ cell count in pre‐apheresis samples could predict the target CD34+ cell yield in the Auto group in 73.4 % of cases. In the Allo group the AUC was 1.0 for HPC and CD34+ cell counts. Only two patients did not achieve the target first apheresis CD34+ cell count yield. Samples collected during the apheresis . The AUC was 0.8561 and 0.7667 for HPC count in the Auto1 and Auto2 groups respectively. In table 1 we show positive and negative HPC cut‐offs. HPC count could predict the target CD34+ cell yield in the Auto group in 33.3 % of cases. The AUC was 1.0 and 0.9250 for CD34+ cell count in the Auto1 and Auto2 groups respectively. See positive and negative CD34+ cell cut‐offs in Table 1. CD34+ cell count could predict the target CD34+ cell yield in the Auto group in 80 % of cases. In the Allo group AUC was 1.0 for HPC count and 0.9821 for the CD34+ cell count. Summary/Conclusion: In the samples collected pre‐apheresis the predictive value of the HPC count and the CD34+ cell count to predict the final apheresis product CD34+ cell yield were 34.6 % and 73.4 % respectively. The HPC count and CD34+ cell count in the samples of apheresis product collected in the middle of the apheresis procedure did not add more useful information in comparison with the samples pre‐apheresis. With regard to the Allo group with healthy donors very few needed more than one apheresis procedures to collect enough stem cells.