Effect of umbilical cord blood prefreeze variables on postthaw viability.

Background: Assessment of the overall postthaw (PT) viability of an umbilical cord blood (UCB) unit is an important criterion for determining the quality of the unit for transplantation. Overall PT viability is a measure of cellular damage that can occur to the UCB during collection, storage, processing, freezing, and thawing.

Study Design And Methods: This study investigated factors measured before freezing of the UCB that could affect overall PT viability of the stem cell unit from 257 collected cord blood samples. The analysis included hematologic variables, cord blood collection characteristics, and stem cell separation and preservation factors.

Results: Each of the variables, postprocess (PP) neutrophils (%), PP hematocrit, overall PP viability (%), freeze rate (°C/min), and time from collection to freezing (hr) were shown to contribute to overall PT viability. Each UCB sample was given a calculated "viability prediction" (VP) score based on the influence or impact of each of these variables. This score was compared to the measured PT viability. Variables with a low VP score had correspondingly low PT viability, indicating more overall damage to the cells. The results showed that the higher the VP score, the higher the PT viability.

Conclusion: These findings provide a framework for identifying those units that are most likely to have a high overall PT viability and hence an increased likelihood of successful engraftment of the CB-sourced stem cells. The VP score could aid in the selection of a donor cord blood unit for transplantation.