Selection of Cord Blood Units Based on CD34+ Cells for Storage in Cord Blood Bank.

Over 170 000 cord blood units are stored worldwide. For the majority of patients in need of an allogeneic donor, a cord blood unit can be found which is identical or has less than 2 HLA mismatches. However, when partially mismatches cord blood units are used for transplantation, the number of CD34+ cells per kg body weight becomes important and should be higher than 1.7 10 5 /kg (Blood2002;100:1611–1618). For this reason, it is important that only cord blood units with high CD34+ cell content are stored. Our standard selection criteria are volume above 40 mL and TNC of 10x10 8 or higher. Using these criteria, we routinely store 18% of collected units. The mean CD34+ cell content of stored units is 5.2 10 6 and TNC is 1.38x10 9 . 94%, 52%, 12%, 4% of cord blood units can be used for patients weighing 10, 25, 50 and 75 kg respectively, based on the criterium of 1.7. 10 5 CD34+ cells/kg patient weight mentioned above. To optimize CD34+ cell content in the stored units, we compared our present selection method based on TNC and volume (criterium 40/10/?) with a selection method based on volume, TNC and CD34 content. 131 samples with volumes above 40mL and TNC above 8x10 8 were analysed for CD34+ cell content before processing and subsequently processed in routine. Using this data set, we compared criterium 40/10/? with criteria 40/8/2 (volume:40mL, TNC:8x10 8 , CD34 2x10 6 ). We found that both criteria resulted in an equal number of units acceptable for storage. CD34+ cell content increased from 4.5x10 6 for criterium 40/10/? to 4.8x10 6 for criterium 40/8/2 whereas TNC dropped from 14.6x10 9 to 14.1x10 9 . 100%, 47%, 9% and 4 % (criterium 40/8/2) vs 88%, 43%, 9% and 4%(criteria 40/10/?) of cord blood is acceptable for patients weighing 10, 25, 50 and 75 kg resp., demonstrating that the 12% essentially unusable cord blood units are replaced by units which can be used for small children. In conclusion: by including CD34+ cell content in the selection criteria, CD34+ cell content increases so that 100% of the cord blood units can be used for children up to 10 kg. This measure however requires that CD34 measurement is performed on all units with TNC above 8x10 8 cells.