CONTAMINATING LEUKOCYTES INFLUENCE THE STORAGE CONDITIONS OF PLATELET CONCENTRATES
Leukocyte poor platelet concentrates (PC), containing less than 10 leukocytes, prepared from buffycoats can be stored in normal PVC bags for 7 days at 22°C without deterioration of the pH. We assumed that a low number of leukocytes present in the PC, is a critical factor to maintain the pH. To test this hypothesis increasing amounts of leukocytes were added to four groups of three PC with comparable plasma volumes (mean 58.6 ± 0.8 (SD) ml) and platelet concentrations (1.01 ± 0.04×109 /ml). Group I had a leukocyte concentration of 0.14±0.048×106 /ml, group II 1.96±0.09×106 /ml, group III 5.53±0.98×106 /ml, and group IV 13.0±0.93×106 /ml. The PC were stored in normal PVC bags for 7 days at 22°C. Measurements in vitro were performed at day 0, 2, 5 and 7.The initial mean pH value was 7.12±0.02 (SD) for all PC and dropped to 6.89, 6.85, 6.77 and 6.61 for group I to IV respectively, at day 7. A significant correlation (Spearman rank test) between low pH values and high leukocytes was found. The same significant positive correlation was observed between high leukocyte concentrations and high glucose consumption and high lactate production and LDH release during storage.These results show that the amount of leukocytes in PC has a significant contribution to the detrimental effect on pH during platelet storage. It is therefore important to prepare PC with a leukocyte count lower than 10 . Moreover the risk of alloimmunisation against HLA antigens will be diminished.