Evaluation of pooled platelet concentrates using prestorage versus poststorage WBC reduction: impact of filtration timing

BACKGROUND: Concern for the undesirable consequences of transfusing passeng er WBCs is leading to the general use of WBC-reduced platelet concentrates (PCs). However, the impact of prestorage versus poststorage WBC reduction o n the quality of platelet products has not been clearly defined. STUDY DESIGN AND METHODS: Pooled PCs were WBC reduced before or after 5-day storage, by use of a WBC filter (PXL-8, Pall Corp.). Samples from pools we re taken on days 1 and 5, before and after filtration, and on Day 9 of stor age and assessed for cell counts, biochemical values, expression of platele t glycoproteins, thrombin generation, and content of IL-6, IL-8, TNF alpha, transforming growth factor beta 1 (TGF beta 1), and anaphylatoxins C3a and C4a. RESULTS: Filtration of fresh and 5-day-stored pooled PCs via a PXL-8 filter was similarly efficient, rendering pools with low WBC counts (<1 x 10(6) c ells) and high platelet recovery (>95%). No major changes were found in the metabolic behavior or the expression of platelet GPIb, GPIIb/IIIa, CD62, a nd CD63 in PCs filtered before or after storage. Filtration, either before or after storage, increased by less than 5 percent the proportion of CD62platelets. Moreover, no changes were found in the concentration of prothrom bin fragments 1 and 2 and thrombin-antithrombin complexes in the pooled PCs derived from the time of filtration. Finally, prestorage WBC reduction abr ogated the accumulation of IL-6 and IL-8, but it did not prevent that of an aphylatoxins C3a and C4a nor of TGF beta 1. However, filtration through a P XL-8 filter significantly reduced (40-90%) the amount of IL-8, C3a, and C4a in the filtrate. CONCLUSIONS: The timing of PXL-8 filtration of PCs has little impact on the efficiency of WBC reduction and on platelet recovery. and it does not seem to affect the quality of platelets or the generation of thrombin in the PC s. As regards the goal of reducing the amount of bioactive products in PCs, it remains uncertain as to whether prestorage WBC reduction fully eliminat es the need for poststorage filtration. Prestorage filtration leads to low levels of IL-6 and IL-8 in PCs, but it does not impair the poststorage cont ent of TGF beta 1 or anaphyla-toxins. By contrast, poststorage PXL-8 filtra tion removes significant amounts of C3a and C4a, and thus it might provide clinical benefits beyond those of prestorage WBC reduction.