CD34+ cell content of 126 341 cord blood units in the US inventory: implications for transplantation and banking

CD34(+) cell dose is critical for cord blood (CB) engraftment. However, the CD34(+) content of the CB inventory in the United States is unknown. We examined the CD34(+) cell content of 126 341 red blood cell-depleted US units banked from January 2007 to September 2017 with a total nucleated cell (TNC) count of >= 90 x 10(7) and a cryovolume of 24-55 mL. Median pre- cryopreservation TNC content was 127 x 10(7) (interquartile range [IQR], 108-156 x 10(7)); CD34(+) cell content was 44 x 10(5) (IQR, 29 to 67 x 10(5)). The median CD34(+):TNC ratio was 0.34%. TNC and CD34(+) cell content correlation was weak (r = 0.24). Of 7125 units with TNCs of >= 210 x 10(7), only 47% had CD34(+) content of >= 100 x 10(5). However, some units had high CD34 +/- content for a given TNC count. Only 4% of CB units were acceptable as single-unit grafts (TNCs, >= 2.5 x 10(7)/kg; CD34(+) cells, >= 1.5 x 10(5)/kg) for 70-kg patients; 22% of units were adequate for 70-kg patients using lower dose criteria (TNCs, >= 1.5 x 10(7)/kg; CD34(+) cells, x 10(5)/kg) suitable for a double-unit graft. These findings highlight that units with the highest TNC dose may not have the highest CD34(+) dose, units with unexpectedly high CD34(+) content (a ratio of > 1.0%) should be verified, and the US CB inventory of adequately sized single units for larger patients is small. They also support the ongoing use of double-unit grafts, a focus on banking high-dose units, and development of expansion technologies.