Leukoreduction of platelet concentrates using a 'polishing' filter

Background and Objectives: Filters for removal of leukocytes from platelet concentrates (PCs) usually have a large volume to guarantee sufficient leuk oreduction, In this study, a small filter, with a volume of only 8 mi and t herefore minimal platelet loss, for leukoreduction of PCs was investigated. This filter has a 'limited' leukoreducing capacity, hence the filter is ca lled a 'polishing' filter. Materials and Methods: PCs were made from 5 pooled buffy coats in either pl asma or additive solution (PAS-II), After centrifugation, the platelet-rich supernatant was expressed on an automated separator (Compomat G4) to an em pty transfer bag. The content of this transfer bag was filtered into the pl atelet storage bag, either by expression by lowering the top press of the C ompomat G4, or by gravity by hanging it on a filtration rack. Results: Leukocyte counts before and after filtration revealed a mean leuko reducing capacity for the filter of 2.67 log(10) and a platelet loss of onl y 2% for PCs in PAS-II (n = 50), and for PCs in plasma a 3.43 log(10) leuko reduction with 3% platelet loss (n = 30). Expression of the PCs both in pla sma and PAS-II through the filter using the Compomat G4 resulted in 10/10 u nits containing <5X10(6) leukocytes, but 1/10 PCs contained >1X10(6) leukoc ytes for both solutions. Filtration by gravity resultet in 40/40 units with <1x10(6) leukocytes for PCs in plasma, and 60/60 units with <1X10(6) for P Cs in PAS-II. Conclusion: The 'polishing' filter allows reliable, standardized and automa ted production of PCs, both in plasma and additive solution with minimal pl atelet loss, and containing uniformly <1X10(6) leukocytes, provided the fil tration procedure is performed by gravity. Copyright (C) 2000 S. Karger AG, Basel.