Removal of Leukocytes from Blood by Fibre Filtration: A Comparison Study on the Performance of Two Commercially Available Filters

Abstract: Two different kinds of filters suitable for the almost complete removal of leukocytes from blood-cell concentrates were tested. The maximal retention of filter I was 1.9-3.4×10⁹ leukocytes per filter, whereas filter II could retain 3.6–7.8×10⁹ leukocytes per filter before the leukocyte concentration in the filtrate passed the level of 500 leukocytes/μl. The leukocytes, once absorbed by the fibre material, could be released by washing the filters I, whereas the leukocytes were retained by the material of the filters II. No detectable particles were released after the first 100 ml of filtrate during the washing procedure of either kind of filters. From more than 20% of the filters I, more than 500 pg/ml of endotoxin could be released during the prewashing, whereas none of the filters II was contaminated with endotoxin. The filter II released acetic acid which could be completely removed during the prewashing with 250 ml of saline solution. Operation according to the prescribed conditions of 25 filters of both kinds revealed that the residual leukocyte content in the filtrate was more than 0.25 ×10⁹ leukocytes in 8 out of 25 of the filtrates when filters I were used, whereas with all filters II, this content remained lower than 0.1×10⁹ leukocytes per filtrate. It was concluded that only filter II has sufficient capacity to guarantee the removal of 97% of all leukocytes and 90% of the thrombocytes present in 500 ml of fresh human blood.