BACKGROUND: Umbilical cord blood (UCB) products have traditionally been thawed using a washing method intended to stabilize the cells, reduce dimethyl sulfoxide (DMSO) toxicity, and remove potentially ABO-incompatible red blood cell (RBC) stroma and plasma. Concerns with this approach include loss of total nucleated cells (TNCs), bag breakage during centrifugation, and poor reproducibility by transplant centers unfamiliar with this technique. We rationalized that a simple 1:1 dilution without centrifugation would stabilize the product and reduce the DMSO concentration by 50%, allowing for a controlled thaw in the laboratory without the risks of cell loss.

STUDY DESIGN AND METHODS: We compared the traditional wash method with albumin reconstitution (dilution) and thaw only (no dilution or wash), assessing measurements of viability, TNC, CD34, and colony-forming cell (CFC) recovery post-thaw. Ten cryopreserved UCB products were thawed, split equally into three parts, and treated using each method. Product stability was measured at multiple time intervals up to 48 hours post-thaw.

RESULTS: Throughout the entire evaluation, traditional wash and dilution methods performed equally well with no significant differences observed in 7-aminoactinomycin viability, TNC, CD34, or CFC recovery. For 163 patients in which diluted products were administered, there were no serious adverse effects at infusion and similar time to engraftment was observed when compared to historical experiences with traditional wash and direct infusion.

CONCLUSION: We conclude that removing DMSO, RBC stroma, and plasma post-thaw using a wash method is not necessary when UCB products are RBC and plasma reduced before cryopreservation.