FlowScore—a formula developed at Oxford University in collaboration with NHS Blood and Transplant—predicts how quickly red blood cells release their oxygen. This process is important for oxygenating the body’s tissues, including organs and muscles, particularly in people receiving large transfusions.

Healthy fresh red blood cells have a distinctive biconcave—or dumbbell—shape for efficient oxygen release. During refrigerated storage, red cells become energetically stressed and more spherical, which slows oxygen release. Using transplant kidneys, researchers at Oxford showed that perfusion with blood units that had undergone storage-related kinetic rundown was associated with poorer oxygen delivery, and that this could be restored by biochemically rejuvenating—or refreshing—the blood.

Factors affecting oxygen release from red cells were described at Oxford’s Department of Physiology, Anatomy, and Genetics but the testing method was too laborious for routine use in blood agencies working to improve the monitoring of blood stored for transfusion. To adapt the research findings to blood banking, NHS Blood and Transplant’s Component Development Laboratory joined the project, providing blood samples stored according to NHS protocols and measurements from hematology analyzers.