The limited number of progenitor stem cells in umbilical cord blood (UCB) 
enforces the optimization and strict control of all the procedures involved in 
its therapeutic use--ie, collection, processing, cryopreservation, thawing, and 
transportation--to ensure graft potency at transplantation. For this reason, 
international UCB standards recommend storage of a cell sample attached to the 
UCB unit as a quantitative and functional control of the unit selected for 
transplantation. To validate the use of the sample attached to the UCB unit as a 
quality-control tool for the final product, UCB units (n = 20) stored in liquid 
nitrogen with the Bioarchive system were analyzed. The UCB units and their 
attached segments were thawed, and the number and viability of total nucleated 
cells, mononucleated cells, CD45 + cells, and CD34+ cells were determined, as 
were colony-forming cell counts. There was no significant difference between UCB 
units and segments for any of the parameters assessed. Additionally, the linear 
correlation coefficient (R2) in these paired samples was 0.85 and 0.78 for CD34+ 
cells and colony-forming cells, respectively. In conclusion, the cell sample in 
the tube segment physically linked to the transplant UCB bag predicts the total 
cell content and functionality of the unit and may serve as a source for final 
quality control of the UCB unit before transplantation.