Biomarkers selection. This figure considers only 8 biomarkers (lactic acid, nicotinamide, 5-oxoproline, xanthine, hypoxanthine, glucose, malic acid, and adenine) to define the metabolic states of RBCs during cold storage. (A) PCA performed on selected extracellular SAGM biomarkers. (B) PCA performed on selected extracellular AS3 biomarkers.