Total Nucleated Cell and CD34+ Content of Cord Blood Units Selected for Unrelated Transplantation: Correlation of Results Provided by the Releasing Cord Blood Bank with the Post-thaw Quality Assurance Testing at Transplant Centers

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Following identification of a human leukocyte antigen-compatible donor, the selection of cord blood units (CBUs) for use in unrelated transplantation is based primarily on the total nucleated cell (TNC) and CD34+ content, which are key determinants of engraftment kinetics and survival. To correlate CBU TNC and CD34+ content assessed post-processing pre-cryopreservation and post-thaw pre-release as reported by the cord blood bank (CBB) with the results generated by transplant centers (TCs) as part of their quality assurance (QA) testing. The QA results were obtained directly from TCs or via the Center for International Blood and Marrow Transplant Research or EuroCord Registry. Eight of 168 CBUs released by the CBB for unrelated transplantation were not infused. Post-thaw TNC and CD34+ data from TCs were available for 112 of 160 (70%) and 110 of 160 (68.8%) CBUs, respectively. Prior to storage in vapor phase liquid nitrogen, CBUs were red blood cell and plasma reduced and controlled rate frozen with the addition of dimethyl sulfoxide and dextran-40 (10% concentration of each in the final product). Testing was performed using validated assays for TNC on automated hematology analyzers and for CD34+ using single platform flow cytometric methods. A high level of correlation between the CBB and TC results was observed (Table 1). This was maintained (r = .85) for post-thaw TNC ≤130 × 107; however, for TNC >130 × 107 the r value was only .69 (data not shown). Correlation of CBB CBU TNC and CD34+ content with TC data ar, Pearson's correlation coefficient. bSignificance of Pearson's correlation coefficients. Abbreviations: CBB, cord blood bank; CBU, cord blood unit; P–P, post-processing; P–T, post-thaw; TC, transplant center; TNC, total nucleated cell count. Correlation of CBB CBU TNC and CD34+ content with TC data ar, Pearson's correlation coefficient. bSignificance of Pearson's correlation coefficients. Abbreviations: CBB, cord blood bank; CBU, cord blood unit; P–P, post-processing; P–T, post-thaw; TC, transplant center; TNC, total nucleated cell count. The CBU TNC and CD34+ content reported by the CBB was highly correlated with the results of QA testing at TCs. This provides confidence in the accuracy and reproducibility of these parameters critical to decision-making and CBU selection and reflects the global advances in standardization of these tests. Discrepancies between the CBB and TC data noted for the post-thaw TNC content above the TNC threshold of >130 × 107 may be explained by technical issues and the need for manual dilutions when there is limited sample availability, indicating the need for additional attention with post-thaw testing.