A recent study has introduced FlowScore, a new metric for evaluating the quality of red blood cells (RBCs) that goes beyond traditional haemoglobin assays. While haemoglobin levels measure oxygen-carrying capacity, FlowScore focuses on the rate at which RBCs unload oxygen, a crucial factor for effective tissue oxygenation. This is achieved by analysing the geometry of RBCs, which influences oxygen diffusion, and linking this to flow-cytometric variables.
The research team used single-cell oxygen saturation imaging to measure the time-constant of oxygen unloading (τ) and then correlated this with FlowScore, a ratio of side- and forward-scatter recorded by a haematology analyser. The study found that FlowScore could differentiate freshly drawn blood from stored RBCs, which undergo metabolic changes and spherical remodelling, hindering oxygen unloading. FlowScore showed a sensitivity and specificity greater than 80% in identifying these storage-related changes.
Furthermore, FlowScore successfully predicted the restoration of oxygen unloading after biochemical rejuvenation of stored blood. It also correlated with the levels of ATP and 2,3-diphosphoglycerate, key metabolic factors in RBC function. The validity of FlowScore was confirmed across four international blood-banking systems in Australia, Canada, England, and Spain.
As a reliable and cost-effective metric, FlowScore has the potential to serve as a valuable quality marker for RBCs in blood-banking and haematology, improving both storage management and clinical outcomes. It could also inform the study of diseases and other factors, such as age, sex, and smoking, that affect RBC function.
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.
