Extended survival of neocytes produced by a new system.

Red cells (RBCs) prepared by a new system using centrifugation to produce neocyte enrichment were studied in two laboratories. The system used a blood bag with a geometric configuration such that younger, less dense cells could be separated from older, denser cells. Phthalate ester density gradient curves determined that neocyte enrichment was 81.3 percent in one laboratory and 82 percent in the other. RBC viability was studied by 51Cr autologous transfusion in normal volunteer donors. A randomized, paired design was used in which each donor was transfused once each with neocytes and with RBCs of all ages. The mean control half-life was 34.8 ± 5.4 days in one laboratory and 34.0 ± 3.6 days in the other. The mean half-life of the neocyte-enriched RBCs was 45.2 ± 8.2 days in one laboratory and 45.1 ± 4.4 days in the other. This represented a more than 30 percent increase in half-life for the neocyte-enriched RBCs, a significant difference. This new system, a two-bag set that costs $15, allows the simple, efficient separation of neocyte-enriched RBCs that would have a longer half-life and could reduce the transfusion requirement in patients receiving chronic transfusion therapy.