Harvest of young red cells on an automated cell separator

Red cells can be fractionated by age on a blood processor (Model 2991, IBM). However, little data exist on processing a product for transfusion. This report details a method for collecting young erythrocyte (YE) units containing a mean hemoglobin content of 56.43 +/- 1.39 (SEM) grams. Enrichment with YEs was indicated by greater activity of the enzyme pyruvate kinase (PK) in aliquots of YE units. The mean ratio of PK activity in the young red cell product compared to unfractionated blood was 1.14 +/- 0.03 (SEM). An increased PK ratio was noted in 23 of 26 units studied. Based on the PK ratio, the mean age of the erythrocytes was 46 days, compared to 60 days for standard units of blood. In the 6 units assayed, the reticulocyte count was increased. Collection of YE units was relatively easy, no untoward donor reactions were observed, and no deleterious effects developed in the recipient. Although these data suggest enrichment with a young population of red cells, YE units produced by this method are experimental. Routine use of this procedure awaits demonstration of a significant decrease in transfusion frequency in patients receiving YE units for chronic red cell therapy.