A simple technique for preparation of young red cells for transfusion from ordinary blood units.

We have developed a rapid and simple method for the isolation of relatively young cells from ordinary fresh or previously frozen blood units, using the IBM-2991 Blood Cell Processor. Based on in vitro measurements of red cell pyruvate kinase activity, the resolution of the method is excellent, comparable to that of the stractan discontinuous gradient system. In splenectomized patients with thalassemia major, the administration of the "youngest" 50% of blood units yielded 51Cr survival times of 40 and 42 days for fresh packed red cells and 41 and 43 days for previously frozen red cells.