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 × 10⁷ and a cryovolume of 24-55 mL. Median pre-cryopreservation TNC content was 127 × 10⁷ (interquartile range [IQR], 108-156 × 10⁷); CD34⁺ cell content was 44 × 10⁵ (IQR, 29 to 67 × 10⁵). 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 × 10⁷, only 47% had CD34⁺ content of ≥100 × 10⁵ 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 × 10⁷/kg; CD34⁺ cells, ≥1.5 × 10⁵/kg) for 70-kg patients; 22% of units were adequate for 70-kg patients using lower dose criteria (TNCs, ≥1.5 × 10⁷/kg; CD34⁺ cells, ≥1.0 × 10⁵/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.