Refrigerated storage of red cell concentrates (RCC) for transfusion is associated with the accumulation of various alterations to the red blood cells (RBCs). Among these, a subpopulation of small RBCs defined as storage-induced microerythrocytes (SMEs) accumulates during storage. The SMEs subpopulation correlates with transfusion recovery. Quantification of this morphologically-altered RBC subpopulation using flow cytometry would be a valuable tool to evaluate RCC quality. In the present invention, RBC obtained at the beginning or at the end of storage from RCC stored in SAGM in blood bank conditions were treated with a carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) staining protocol and were finally analysed by flow cytometry to assess the intensity of CFSE staining. The inventors observed the accumulation of a CFDA-SEhigh subpopulation by flow cytometry that accounted for 0.8% and 36.3% at day 3 and 42 of storage, respectively. Images confirmed that the CFDA-SEhigh subpopulation mostly contains SMEs. Thus SMEs can now be simply quantified using a common fluorescent dye and a standard flow cytometer.