Validation of the Cord Blood (CB) APGAR Score System to Predict Neutrophil Engraftment of Plasma Depleted CB Products

Abstract 3549

Cord blood potency is important for transplantation product selection, and various tests have been proposed to measure potency and predict engraftment potential, such as total nucleated cell dose (TNC), CD34⁺ cell dose (CD34), and colony forming unit dose (CFU). Though TNC has been the most widely used measure for CB selection to date, its predictive value is not as robust as the progenitor cell measurements. Unfortunately, most progenitor cell tests suffer from high inter-bank/laboratory coefficient of variance (CV) - decreasing the clinical utility of these tests as potency measures. Recently, the Duke Group proposed a CB APGAR scoring system composed of (1) a Pre-Cryopreserved Score (PCS) reflecting pre-freeze TNC, CD34, CFU and CB collected volume, as well as a (2) Composite Score (CS) which combines the PCS score with post-thaw TNC, CD34, CFU and mononuclear cell dose (MNC). Based on single, myeloablative and first transplants of mostly pediatric patients performed at a single institution (Duke) and using largely red cell reduced CB, the PCS and CS scores have been shown to be predictive of neutrophil and platelet engraftment probability. With CIBMTR-audited outcome data of transplanted CB products from a large multi-national CB bank, we sought to validate the CB APGAR system (1) on a patient population made up of mostly adults, (2) with heavy representation of minority and international patients, (3) on both single myeloablative and first transplants, as well as (4) other types of transplants, and lastly (5) using plasma depleted (red cell replete) CB products. The table below shows the day 42 neutrophil engraftment probability (ANC500) comparison of the original Duke data with StemCyte transplants using PCS and CS scores for both single, myeloablative and first transplants (SMF) and all transplants (All). For each of the PCS and CS strata that were compared, neutrophil engraftment probability appeared to be similar among the Duke SMF, StemCyte SMF and StemCyte All cohorts. We conclude that the Duke CB APGAR score, especially the PCS score, may serve as an easy-to-use and reproducible potency measurement that is highly predictive of neutrophil engraftment probability for (1) red cell reduced as well as plasma depleted CB, (2) for pediatric patient population as well as for mixed populations of adults and children, and (3) for minority and international patients. Lastly, the CB APGAR appears to be applicable to cord blood units with or without RBC depletion providing a tool that can be used for units processed and stored by various methods at different cord blood banks.