Changes in agglomeration of human red blood cells in liquid storage in CPD media

A procedure which may distinguish between old and new CPD blood units in liquid state is described. It is based on the observation of increased tendency to reversible agglomeration in old erythrocytes in liquid preservation. Erythrocytes clump together when they are mixed with low ionic strength solutions in pH range of 5.2 to 6.5. We found that liquid-stored erythrocytes show an augmented tendency to agglomerate in 0.24M sucrose, pH 7.2. The tendency increases with storage so that in the fourth week, more than 70% of the units show agglomeration under these conditions. The addition of minute amounts of sodium chloride may prevent agglomeration. As the cells age, higher salt concentration is required to prevent agglomeration. A short incubation of washed cells with adenosine may reverse the tendency of outdated erythrocytes to agglomerate, concomitantly with reestablishment of initial ATP level. However, depletion of the ATP of fresh cells with fluoride does not induce agglomeration. A 20 hour incubation of units at 37 C with CPD revealed an increased sensitivity of older units, with low ATP and positive agglomeration. This test may help in distinguishing between outdated and younger units in the blood bank.