Analysis of Plasma Products for Cellular Contaminants: Comparing Standard Preparation Methods

Abstract

Background: Recent reports suggest that component plasma products contain significant quantities of cellular contamination. We hypothesized that leukoreduction of whole blood before preparation of derived plasma is an effective method to prevent cellular contamination of stored plasma.

Study design: Samples of never-frozen liquid plasma prepared by standard methods (n = 25) were obtained from 3 regional blood centers that supply 3 major trauma centers. Samples were analyzed for leukocyte and platelet contamination by flow cytometry. To determine if leukoreduction of whole blood before centrifugation and expression of plasma prevents cellular contamination of liquid plasma, 1 site generated 6 additional units of liquid plasma from leukoreduced whole blood, which were then compared with units of liquid plasma derived by standard processing.

Results: Across all centers, each unit of never-frozen liquid plasma contained a mean of 12.8 ± 3.0 million leukocytes and a mean of 4.6 ± 2 billion platelets. Introduction of whole blood leukoreduction (LR) before centrifugation and plasma extraction essentially eliminated all contaminating leukocytes (Non-LR: 12.3 ± 2.9 million vs LR: 0.05 ± 0.05 million leukocytes) and platelets (Non-LR: 4.2 ± 0.3 billion platelets vs LR: 0.00 ± 0.00 billion platelets).

Conclusions: Despite widespread belief that stored plasma is functionally acellular, testing of liquid plasma from 3 regional blood banks revealed a significant amount of previously unrecognized cellular contamination. Introduction of a leukoreduction step before whole blood centrifugation essentially eliminated detectable leukocyte and platelet contaminants from plasma. Therefore, our study highlights a straightforward and cost-effective method to eliminate cellular contamination of stored plasma.

Figure 1.

Leukocyte contamination of never-frozen liquid plasma.

Figure 2.

Platelet contamination of never-frozen liquid plasma.

Figure 3.

Leukoreduction (LR) of whole blood before centrifugation prevents cellular contamination of plasma units.

Figure 4.

Plasma expressor.

Figure 5.

Standard method for creation of non-leukoreduction (non-LR) plasma from whole blood centrifugation. (1) Whole blood is donated, (2) the whole blood is centrifuged, causing the unit to separate into 3 layers (plasma, buffy coat, and red blood cells), (3) the plasma layer is squeezed out of the top of the bag using a plasma expresser (Fig 4), and the technician will stop the expression when cells from the buffy coat enter the line, (4) the remaining buffy coat and red blood cells are put through a cellular reduction filter (grey box represents the position of the LR filter), which removes all leukocytes and platelets. The final products of this method create a unit of LR-packed red blood cells (PRBC) and unit of non-LR plasma.

Figure 6.

Method for creation of LR plasma from whole blood centrifugation. (1) Whole blood is donated, (2) the whole blood is then put through a cellular reduction filter before (3) centrifugation, which separates the LR whole blood unit into 2 distinct layers (plasma and red blood cells), (4) the plasma layer is squeezed out of the top of the bag using a plasma expresser until the red blood cells are in the line, (5) the remaining red blood cells are already LR. The final products of this method create a unit of LR-PRBC and unit of LR plasma.