FACTORS INFLUENCING WHITE CELL REMOVAL FROM RED-CELL CONCENTRATES BY FILTRATION

Background: The preparation of blood components by hard centrifugation results in red cell concentrates with a small amount of plasma. The i nfluence of various plasma factors, temperature, and storage time on w hite cell reduction by filtration was studied. Study Design and Method s: Red cell concentrates were suspended in 100 mL of saline-adenine-gl ucose-mannitol (SAGMAN) solution or in SAGMAN solution in which 5 or 1 0 mL had been replaced with an equal amount of fresh plasma, albumin ( 4%), or heat-inactivated plasma, After overnight storage at 4 degrees C, filtration at a slow flow rate (2 hours) was performed. The effect of temperature was studied by filtration al 4 degrees C and 37 degrees C. To study the influence of storage time, red cell concentrates were stored for 4 to 8 hours or 14 to 20 hours al 4 degrees C and filtered through another model of filter. The number of white cells was counte d microscopically or by flow cytometry. Results: When 5 or 10 mL of pl asma was added, a significantly smaller number of white cells were fou nd after filtration than were found in the SAGMAN control (the median difference between pairs: 23.6 x 10(6) for 5 mL [p = 0.006] and 14.9 x 10(6) for 10 mL [p = 0.003]). The number of white cells was significa ntly higher with 10 mL of albumin than with 10 mL of plasma (differenc e, 15.0 x 10(6); P = 0.006). When heat-inactivated plasma was used, th e number of white cells was significantly lower than when fresh plasma was used (difference, 0.3 x 10(6); p = 0.009). Filtration at 37 degre es C resulted in a 64-percent reduction in white cells and that at 4 d egrees C led to a 99.7-percent reduction (p = 0.006). When the second filter was used, a slight but significantly lower number of white cell s was found in the red cell concentrate stored for 14 to 20 hours than in that stored for 4 to 8 hours (difference, 0.03 x 10(6); p<0.001). Conclusion: The amount of plasma in the red cell concentrate and the s torage time and temperature are important factors in the outcome of wh ite cell reduction by filtration. The effect of plasma does not seem t o be due to a general influence of protein or to the activity of compl ement or fibrinogen.