White cells in fresh-frozen plasma: evaluation of a new white cell-reduction filter

Fresh-frozen plasma (FFP) has generally been regarded as an acellular component. Recently, viable lymphocytes have been detected in this component and the question of irradiation of FFP for certain patients has been raised. Whether the numbers of white cells (WBCs) in FFP are sufficient to require WBC-reduction of acellular components for patients receiving WBC-reduced cellular components has not been determined. WBC numbers in FFP were examined, and the performance of a new commercial WBC-reduction filter for FFP was assessed.

WBC numbers in plasma processed for use as FFP and in thawed FFP were counted before and after WBC-reduction filtration by the use of flow cytometry Fast and slow filtration was used to simulate laboratory and bedside filtration, respectively. Three different methods for plasma harvesting (soft-spin, hard-spin, and second-spin methods) were assessed. The filter capacity was also examined.

The numbers of WBCs in plasma covered a three-log10 range (soft-spin method, 0.04-3.6 x 10(6); hard-spin method, 0.47-45.4 x 10(6); second-spin method, 0.4-37.2 x 10(6)). For the hard-spin and second-spin methods which produced the greatest plasma yields, 92 percent and 85.7 percent of bags, respectively, had counts >1 x 10(6) and 43 percent (hard-spin method) and 45.7 percent (second-spin method) had counts >5 x 10(6). There was no significant difference between the counts obtained in plasma and thawed FFP. The filter reduced WBC numbers to <1 x 10(5) in all but 3 of 49 bags. In the remaining three, there were <2 x 10(5) WBCs. Five bags of plasma could be processed effectively through each filter.

FFP may contain WBC numbers above the threshold at which the use of WBC-reduction filters for cellular components in some patients is necessary. Confirmation of these findings and similar investigations on plasma prepared by other methods may help in defining a role for the use of WBC-reduction filters for FFP