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Summary: All‐trans‐retinoic acid (ATRA) and arsenic trioxide (ATO) represent the standard of care for low‐intermediate risk acute promyelocytic leukaemia (APL). Leucocytosis during induction with ATRA‐ATO represents a common complication with an incidence of up to 60%. To identify predictive factors for this complication, we studied a cohort of 65 low‐intermediate risk APL patients treated with ATRA‐ATO in three highly specialized Italian centres. Overall, 39/65 (60%) patients developed leucocytosis, with a peak in leucocyte count being most frequent in the second week from diagnosis. All cases were successfully managed with hydroxyurea. Predictive factors for leucocytosis in univariate analysis were lower platelet counts (odds ratio [OR] 0.98, 0.97–1.00, p = 0.018), lower fibrinogen levels (OR 0.36, 0.17–0.66, p = 0.003), higher bone marrow blast infiltration (OR 1.03, 1.01–1.07, p = 0.021) and CD117 expression by flow (OR 1.04, 1.01–1.08, p = 0.012). Multivariate analysis confirmed lower levels of fibrinogen at diagnosis as the strongest predictive factor for the development of leucocytosis (OR 0.36, 0.15–0.72, p = 0.009). Differentiation syndrome (DS) occurred only in patients developing leucocytosis showing a strict correlation with rising leucocytes counts (16/39 vs. 0/26, p < 0.001). In addition, other treatment‐related complications including QTc prolongation, cardiac events, liver, and haematological toxicities were significantly more frequent in patients experiencing leucocytosis (22/39 vs. 3/26, p < 0.001). In conclusion, APL patients undergoing ATRA‐ATO therapy with lower fibrinogen levels and platelet counts at diagnosis and with a massive bone marrow blast infiltrate should be carefully monitored for the development of leucocytosis during induction. DS and other treatment‐related complications seem to occur almost exclusively in patients developing leucocytosis, who should necessarily receive DS prophylaxis and more intensive monitoring and supportive therapy to prevent treatment complications. [ABSTRACT FROM AUTHOR]

Background In our Center, the cell viability, the integrity of the bag, and the clonogenic assay were evaluated before the reinfusion of hematopoietic progenitor cells-apheresis ( HPC-A). This quality control (QC) should be made 14 days before the reinfusion to the patient to have the result of the functional test on the proliferative capacity of hematopoietic progenitors. Study Design and Methods This study was designed to assess the potential of an automatic cell counting system ( Nucleo Counter NC-3000, Chemo Metec) in our clinical routine as a support of the clonogenic assay and the cytofluorimetric analysis for the QC of the cryopreserved HPC-A. The cell viability was evaluated by flow cytometry using the modified International Society of Hematotherapy and Graft Engineering protocol. The proliferative potential was assessed by specific clonogenic tests using a commercial medium. Furthermore, we evaluated the cellular functionality with Nucleo Counter NC-3000, by using two protocols: 'vitality assay' and 'mitochondrial potential assay.' Results The evaluation of the total nucleated cells in preapoptosis measured by 5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazol-carbocyanine iodide ( JC-1) assay showed a negative correlation (r = −0.43) with the total number of colonies (colony-forming unit [CFU]-granulocyte-macrophage progenitors plus burst-forming unit-erythroid progenitors plus CFU-granulocyte, erythroid, macrophage, megakaryocyte progenitors) obtained after seeding of 50 × 106/ L viable total nucleated cells. We observed a significant difference (p < 0.0001) comparing the median number of colonies (166.70; SD, ±136.36) obtained with a value of JC-1 less than 30% to the number of colonies (61.75; SD, ±59.76) obtained with a value of JC-1 more than 30%. Conclusion The evaluation of cell functionality by the use of the Nucleo Counter NC-3000 is in agreement with results from clonogenic assay and can be considered an effective alternative in the routine laboratory. [ABSTRACT FROM AUTHOR]