Highly specific functional equivalence of XN-HPC for optimum CD34+ cell count in harvested allogeneic bone marrow stem cell products

Objectives To establish a reliable XN-HPC cutoff, for an effective CD34 + cell count of ≥2 × 106cells/kg of the recipient’s body weight, in harvested bone marrow products in allogenic transplantation.Methods The study was carried out in two phases. In retrospective Phase 1, data from 47 donors were analyzed. Sysmex analyzer XN-20 and BD FACS Calibur were employed to process XN-HPC and CD34 + cell enumeration, respectively. To make the two variables comparable, both XN-HPC and CD34 + cell counts were reported as the number of cells/kg of the recipient’s body weight. Spearman’s rank correlation coefficient was calculated for CD34 + cells and XN-HPC, followed by the calculation of the receiver operating characteristic (ROC) curve to identify the XN-HPC value which could effectively predict the cutoff of ≥2 × 106 CD34 + cells/kg of the recipient’s body weight. In Phase 2, the computed XN-HPC cutoff was validated in a prospective set of 53 donors by obtaining the positive and negative predictive values.Results Statistically significant correlation was obtained between XN-HPC and CD34 + cell count with Spearman’s rho of 0.54 (p-value <0.001). The optimal XN-HPC cutoff, for the required CD34 + ve cell count of ≥2 × 106 cells/kg of the recipient’s body weight, was calculated to be ≥2.80×106 cells/kg of the recipient’s body weight with the specificity and sensitivity of 100% and 31%, respectively. The ROC curve demonstrated the area under the curve to be 0.74. Phase 2 validation revealed 100% PPV.Conclusions For harvested bone marrow products with XN-HPC of ≥2.80×106 cell/kg of the recipient’s body weight, CD34 + cell enumeration by flow cytometry can safely be disposed of.