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.