Red blood cell preservation by droplet freezing with polyvinylpyrrolidone or sucrose-dextrose and by bulk freezing with glycerol.

BACKGROUND

Red blood cell (RBC) preservation is essential to transfusion medicine. Many blood group reference laboratories need a method to preserve rare blood samples for serologic testing at a later date. This study offers a comparison of three common cryoprotective agents and protocols used today: bulk preservation with glycerol and droplet freezing with sucrose-dextrose (S+D) or polyvinylpyrrolidone (PVP).

STUDY DESIGN AND METHODS

Human blood from 14 volunteers was collected and frozen at set intervals over 2 weeks with PVP, S+D, or glycerol. The frozen RBCs were later thawed and the percentage of surviving RBCs was determined. Detailed protocols and an instructional video are supplied.

RESULTS

Over a 2-week period, RBCs preserved with glycerol and thawed with a widely used protocol showed a recovery of 41 ± 16% (mean ± standard deviation) while those thawed with a modified glycerol protocol showed a recovery of 76 ± 8%. RBCs preserved by droplet freezing with S+D showed a recovery of 56 ± 11% while those preserved by droplet freezing with PVP showed a recovery of 85 ± 6%. Recovery values were similar with ethylenediaminetetraacetic acid or heparin anticoagulants, differing freezing rates, and varying droplet volumes.

CONCLUSION

Droplet freezing with PVP offered the greatest recovery. While bulk freezing with glycerol can also be effective, droplet freezing may be a more convenient method overall. It requires less effort to thaw, needs much less storage room, and allows blood group laboratories to be frugal with thawing rare samples.