Transplantation with stem cells from stored umbilical cord blood units is an alternative to living unrelated bone marrow transplantation. Both are used to treat leukemia, multiple myeloma, and a handful of rare blood diseases. Because the quality of the human leukocyte antigen (HLA) match between recipient and donor is a key determinant of transplant outcome, it is important that transplant candidates have access to a large number of stored cord blood units from which to find a suitable match.

Currently, transplant candidates must conduct separate searches of each of the 22 non-profit “banks” that collect and store donated cord blood. In 2003 Congress appropriated $10 million to create a national cord blood bank in order to streamline the search process. In this study, commissioned by the Institute of Medicine, we used cost-effectiveness analysis to determine how many cord units a national bank should place in storage. The larger the inventory, the greater the likelihood that transplant candidates will match to a stored unit. However, processing new cord blood units is costly, so the access benefits must be weighed against the collection and storage costs.

METHODS

We estimated the likelihood that transplant candidates will match to a cord blood unit as a function of the inventory level based on the distribution of HLA types in the National Marrow Donor Program registry. We calculated life years gained based on these probabilities, historical survival data, and assumptions about patients' preferences for cord blood versus marrow donors when both types of matches are available. (The time to transplant with cord blood is shorter and matching requirements are less stringent, but the volume of stem cells obtained is less than for a living donor). Separately, we used a differential equation describing the cord inventory level to estimate total costs as a function of inventory.

RESULTS

The cost per life year gained associated with increasing inventory from 50,000 to 100,000 units is $38,000-$75,000 and from 100,000 to 150,000 units is $59,000-$142,000, depending on the assumption about the degree to which survival rates for cord transplants vary by donor-patient match quality.

CONCLUSIONS

Assuming the monetary value of a year of life exceeds $100,000, it is cost-effective for a national bank to maintain an inventory of 100,000-150,000 units.