“…Previous studies have shown that RBCs maintain their rheological properties, antigenic pattern and usability for serologic testing after freezing (Bronson & McGinniss, ; Pegg et al ., ; Henkelman et al ., ). Although the freezing of RBCs in glycerol is widely used by blood group reference laboratories (Smith, ; Högman et al ., ), the preservation in liquid nitrogen by droplet freezing, using non‐permeable CPAs such as polyvinylpyrrolidone (PVP) and sucrose–dextrose solution (S + D), has emerged as an effective alternative for the cryopreservation of small aliquots of erythrocytes for posterior use in serological tests (Schmid et al ., ).…”