A NEW method for evaluating the functional quality of red blood cells (RBCs) could transform blood banking and clinical practices by providing a more accurate measure of how well RBCs deliver oxygen to tissues. While haemoglobin assays commonly assess the oxygen-carrying capacity of blood, the rate of oxygen exchange, crucial for tissue oxygenation, has often been overlooked. Researchers have now developed a new metric, called FlowScore, which evaluates RBC oxygen-unloading kinetics based on cell geometry.
The team combined single-cell oxygen saturation imaging with flow-cytometric data from haematology analysers to assess the time-constant of oxygen unloading (τ) in RBCs. They discovered that the geometric shape of RBCs significantly influences oxygen unloading, and this can be quantified using FlowScore, which uses a ratio of side- and forward-scatter.
FlowScore showed remarkable promise in distinguishing freshly drawn blood from stored blood, with over 80% sensitivity and specificity. Stored RBCs often undergo metabolic decline and spherical remodelling, which impairs their oxygen unloading. FlowScore also accurately predicted the restoration of oxygen unloading in stored RBCs upon biochemical rejuvenation. Furthermore, the metric was able to estimate the levels of ATP and 2,3-diphosphoglycerate, key molecules involved in oxygen unloading.
The utility of FlowScore was validated across blood-banking systems in Australia, Canada, England, and Spain, and it was confirmed as a reliable predictor of the time-delay between sample collection and measurement. The method also highlighted that factors such as age, sex, and smoking can affect RBC function.
FlowScore presents a cost-effective, accessible, and reliable tool for assessing RBC quality, making it an ideal candidate for widespread use in blood banks and haematology, where oxygen delivery is crucial.
Helena Bradbury, EMJ
Reference
Rabcuka J et al. Assessing the kinetics of oxygen-unloading from red cells using FlowScore, a flow-cytometric proxy of the functional quality of blood. 2024;111:105498.
