In-Line Leukocyte Depletion of Thrombocyte Apheresis Concentrates

Abstract

Background: This study reports on the filtration efficiency and on functional changes of platelets filtered with the new Fresenius C4F thrombocyte apheresis set. Material and Methods:72 platelet concentrates were collected with a Fresenius AS 104 cell separator. Leukodepletion was performed with a leukocyte adsorption filter (Biofil P plus), integrated into the disposable apheresis system (C4F Fresenius). Residual leukocytes were counted microscopically using a Nageotte chamber. Granule membrane protein 140 (GMP-140) expression was determined by flow cytometry. Additionally, plasma β-thromboglobulin and platelet aggregation (ADP, collagen) were examined. Results:Filtration reduced the number of residual leukocytes from 27.6 ± 34.9 ×?10⁶/unit (mean ± SD) to 0.45 ± 0.6 ×?10⁶/unit (maximum 2.8 ×?10⁶/unit). The median leukocyte reduction was 98.5% (50–99.9%), and platelet recovery was 91.5% (72.6–99.3%). Filtered platelets showed a significant decrease of in vitro aggregability (p < 0.005) but neither significant release of β-thromboglobulin nor increased expression of GMP-140. Conclusion:In-line filtration with the Biofil P plus resulted in adequate leukocyte depletion and good platelet recovery. Filtration did not induce a release reaction ?β-thromboglobulin). Additionally filtered platelets did not show increased activation (GMP-140) but a decreased in vitro aggregability. The latter may be due to a selective retention of activated platelets by filter or the early time of filtration (1 h after separation). Whether the reduced in vitro aggregability is of clinical relevance is rather questionable.