Comparison of a conventional quadruple-bag system with a 'top-and-bottom' system for blood processing.

'Top-and-bottom' bags have an outlet at the top and at the bottom of the collecting bag, allowing simultaneous expression of plasma and red cells, whereas the buffy coat remains in the collecting bag. The composition of blood components was investigated following manual separation of whole blood in a conventional 4-bag system (A) or automated separation in a 'top-and-bottom' system (B). To overcome inter-donor differences, two units of whole blood were pooled and redistributed into the original bags (A and B) prior to centrifugation. Leukocyte-poor platelet concentrates (LPPC) were manufactured from both types of buffy coat (A and B). The volumes of plasma, red cell concentrates (RCC) and buffy coat were similar in both methods. However, the residual leukocytes and platelets in the RCC from the top-and-bottom system were significantly lower than in the conventional system, 140 +/- 59 x 10(6) (mean +/- SD) versus 762 +/- 228 x 10(6), respectively (p less than 0.01). Both types of LPPC contained less than 10(7) leukocytes and could be stored for 7 days maintaining a pH above 6.5. We conclude that the top-and-bottom system enables automated and standardized preparation of RCC and plasma with a significantly better buffy-coat removal than with manual processing.