Differences in residual white blood cell subset counts in buffy coat-depleted red cell concentrates prepared with bottom and top or quadruple-bag systems.

Background: For preparation of buffy coat-depleted red cell concentrates (RCCs) in additive solution whole blood is currently collected in The Netherlands both in quadruple-bag and bottom and top bag systems. By using the quadruple-bag system both plasma and buffy coat cells are transferred into integrated satellite bags while the red cells remain in the collection bag. When bottom and top bags are used, the buffy coat remains in the collection bag while both red cells and plasma are transferred into satellite bags. The difference in processing prompted us to perform quantitative analysis of residual WBC subsets in buffy coat-depleted RCCs. Differences in removal of specific cells with the buffy coat could improve the outcome of additional filtration procedures aiming at complete removal of specific WBC subsets.

Study Design And Methods: The buffy coat was removed in semiautomated procedures (Optipress I; Compomat G4) from units of whole blood collected in both bag systems. Paired samples were taken before and after removal of the buffy coat for counting and analyzing WBC subsets by flow cytometry using subset-specific monoclonal antibodies.

Results: All RCCs met the criteria from the guidelines of the Council of Europe. The percentage of residual total WBCs was lower (p<0.001) in RCCs processed in bottom and top bag systems (26% Compomat and 18% Optipress) as compared to RCCs processed in quadruple-bag systems (43% Compomat). WBC subset analysis in RCCs processed in quadruple-bag systems showed approximately 25% of residual T cells, B cells and monocytes and 60% of residual granulocytes. In contrast, WBC subset analysis in RCCs processed in bottom and top bag systems showed approximately 2% residual T cells, B cells, and monocytes and 35% residual granulocytes; in about 45% of units, lymphocytes and monocytes were even below the detection limit of flow cytometry analysis.

Conclusion: Buffy coat-depleted RCCs are currently processed in bottom and top bag or quadruple-bag systems, the former being superior to the latter due to selective depletion of lymphocytes and monocytes by 98% (2 logs). The bottom and top procedure is an evident contribution to leukodepletion in blood transfusion, both with and without additional filtration.