Procoagulant activity of long-term stored red blood cells due to phosphatidylserine exposure

Objective/Background: Phosphatidylserine (PS) exposure on the outer membrane surface is a known storage lesion of red blood cells (RBCs). Procoagulant activity (PCA) of PRBC units has been shown to increase during storage. However, the PCA and the relation to PS of banked RBCs remain unknown. The aim of this study is to investigate the PCA and the correlation with PS exposure on banked RBCs. Materials and Methods: Human normal leucodepleted RBC concentrates were stored in saline-adenine-glucose-mannitol (SAGM) solution at 4 degrees C for up to 42 days. PS exposure was measured by lactadherin and annexin V. PCA of RBCs was determined by one-step recalcification assay and further determined by prothrombinase and tenase assays. The correlation between PCA and PS exposure of RBCs was measured by inhibition tests with lactadherin or annexin V. Results: Lactadherin detected 1 center dot 5% PS-positive stored RBCs vs 0 center dot 5% for annexin V after 14 days of storage, which significantly reached 18 center dot 4 vs 4 center dot 5% after 42 days of storage. Potent PCA was observed on day 14 and continuously increased. PCA of RBCs on day 42 was inhibited 94% by lactadherin vs 45% by annexin V. Incubation at 37 degrees C in fresh heparinised plasma partially reversed PS exposure and PCA of RBCs stored for 14 days but had no effect on these parameters for cells stored for 42 days. Conclusions: PCA and PS exposure of stored RBCs increased during storage and showed significant positive correlation. PCA of long-term stored RBCs may not be reversed by transfusion.