Background and objectives: Whole blood can be separated by hard spin centrifugation into layers of blood components according to their specific gravity. The aim was to develop a program for an automatic separator to subsequently express the various components into their respective satellite bags in top and bottom systems with the following requirements: a red cell concentrate with a low leukocyte and platelet contamination, a 'cell-free' plasma, and a buffy coat with a volume of about 50 ml with an acceptable loss of red cells.
Materials and methods: The Compomat G4 possesses an independently moving upper and lower press, to automatically express plasma or red cells to satellite bags of top and bottom systems. The influence of the extension of the lower press was studied by pooling and dividing two units of whole blood, and separating these units after centrifugation (2,960 g, 10 min) either with a program where the lower press was completely extended (program C), or with a program that left approximately 1 mm between the door and the lower press (program D).
Results: The program (program D), where the lower press was not completely extended, yielded a buffy coat with a volume of 52+/-1 ml (mean +/- SD, n = 36), which contained >75% leukocytes and >90% platelets of the original whole blood unit, with a red cell loss in the buffy coat of 21+/-1 ml (10.8+/-0.8% of the original volume). The leukocyte content of the red cell concentrates was 775+/-379x10(6) per unit, whereas the plasma contained 3+/-3x10(6) leukocytes and 4+/-3x10(9) platelets per unit. The pooling experiment indicated that complete extension of the lower press (program C) resulted in a significantly higher leukocyte contamination of the red cell concentrate (788+/-431x10(6 ) vs. 658+/-419x10(6); n = 12; p = 0.03), while there was no difference in the yield of red cells or plasma. The buffy coat produced with program D contained significantly more leukocytes (2,242 +/-396x10(6) vs. 2,065+/-327x10(6), p = 0.005) and more platelets (96+/-14x10(9) vs. 92+/-17x10(9), p = 0.02) per unit than with program C, probably because buffy coat cells sticking to the container wall are not expressed to the red cell concentrate, and thus remain in the buffy coat bag. Therefore, program D met our specifications for blood products.
Conclusions: The Compomat G4 warrants reproducible separation of whole blood in top and bottom bags into red cells, buffy coat and plasma meeting our specifications.