Evaluation of a new leukocyte removal filter, the R-S350, in a closed system.

The new high-performance R-S350 leukocyte removal filter was developed to deplete leukocytes from red cell concentrate and whole blood with high efficiency, that is, a higher than 4-log reduction. When 1 unit of red cell concentrate stored for 1 to 2 days was applied, the leukocytes were removed by 4.77 logs with 86.4% red cell recovery and the average filtration time was 15.5min. The average number of residual leukocytes was 4.56±6.74×104/unit (n=25). The R-5350 is also able to remove leukocytes from freshly drawn or 1-day-stored whole blood in a closed system. The leukocyte removal rate was 4.60 logs for fresh whole blood and 4.88 logs for blood stored for 1 day. Platelet removal rates were 2.4 to 2.8 logs and red cell recovery was about 90%. The filtration time was less than 15min for fresh whole blood. During storage of red cell concentrates prepared from filtered or nonfiltered whole blood for 3 weeks at 4°C, neither the ATP and 2, 3-DPG levels nor the morphological score of red cells significantly differed between the two types but the level of supernatant hemoglobin was less in the filtered red cell concentrates.A closed system with a leukocyte-removal filter has advantages for the extension of the storage period for more than 24 hours and keeps the cells in better physiological condition. The new R-5350 filter can be used in a closed system for leukocyte removal from whole blood before storage and is expected to be useful for the prevention of alloimmunization and other side effects of blood transfusion.