Processing: Must cord blood be processed before storage?

The earliest cord blood transplants were performed with whole cord blood.  Thus, it is not absolutely necessary to process cord blood in order to save patient lives.  There has never been a prospective randomized trial to compare transplant patient outcomes with cord blood that had been stored whole versus processed.

Most cord blood banks, both public and private, now process cord blood to remove both the plasma and the red cells, and cryo-preserve the remaining buffy coat holding stem cells.  Some banks also save the removed red cells and plasma in companion storage.  Some banks save a sample of maternal blood.

The removal of plasma is also called volume reduction.  The volume reduction enables more collection units to fit in a freezer and requires less cryogenic nitrogen per unit.

Also, the majority of banks remove red blood cells prior to freezing, primarily because these cells often burst during freezing and release iron from hemoglobin that can be toxic.  The alternate to removing the red cells before freezing is to wash any broken cells out of the collection upon thaw.  Removing the red cells also removes the donor's blood type (the ABO and Rh types).  When cord blood goes from a donor to a patient for a transplant, the donor and patient can be compatible on all the HLA types used for transplant matching and still have incompatible red blood types.