Viable CD34+ stem cell content of a cord blood graft: which measurement performed before transplantation is most representative?

BACKGROUND

Patient survival in allogeneic cord blood transplantation is critically dependent on total nucleated cell (TNC) count or total CD34+ cell count per kg of body weight. Theoretically, viable CD34+ cell measurement at the time of infusion should give a better indication of the suitability of a certain transplant. The relation between measurements on different samples and viable CD34+ cell count on the graft itself was analyzed.

STUDY DESIGN AND METHODS

Viable CD34+ cells were measured with a no-wash, single-platform technique with 7-aminoactinomycin D. Analysis was performed before freezing on the cord blood, after freezing and thawing on the cord blood unit itself, and on various samples.

RESULTS

Cord blood volume correlated poorly with viable CD34+ cell content (r=0.24) as did initial TNC count and WBC count (r=0.57 and r=0.48, respectively). In contrast, viable CD34 cell content determined before freezing correlated well with viable CD34 cell content of the graft (r=0.91) but was on average 25 percent higher than after freezing and thawing. The best correlations with the CD34+ cell content of the cord blood unit were obtained with CD34 cell measurements on a separate cryovial (r=0.95). These CD34 cell measurements on frozen samples were found to be very reproducible (r=0.96).

CONCLUSION

Viable CD34 cell count of the graft is both accurate and precise when measured on a separate sample frozen together with the cord blood unit. This measurement can be performed by the transplant center to exclude between-laboratory variability.