A comparison of washed and volume-reduced platelets with respect to platelet activation, aggregation, and plasma protein removal.

BACKGROUND

Washed or volume-reduced platelets (PLTs) are occasionally requested for patients with a history of allergic or anaphylactic transfusion reactions. However, conclusive data are not available as to which method is more suitable.

STUDY DESIGN AND METHODS

A direct comparison of saline-washed and volume-reduced PLTs was performed by splitting 11 units of 6-day-old apheresis PLT units. PLT activation, aggregation, plasma protein, and PLT count were determined before and after each procedure. To assess whether washing using neutral, calcium-free Ringer's acetate (NRA) would better preserve PLT function, 8 additional units of apheresis PLTs were split and were washed in saline or NRA.

RESULTS

Saline washing resulted in significantly increased number of activated, P-selectin-expressing PLTs compared to volume reduction (24.2% vs. 10.3%, p = 0.001). Aggregation was also significantly reduced (-40.6% vs. -0.8%, p = 0.004). Plasma protein removal was significantly better for saline-washed than volume-reduced PLTs (96% vs. 51.1%, p < 0.001). PLT recovery was not significantly different for saline-washed versus volume-reduced PLTs (70.5% vs. 80.7%, p = 0.079). There was no difference between washing in saline or NRA with regard to PLT activation and loss of aggregation.

CONCLUSIONS

PLT washing with saline or NRA significantly increases PLT activation and decreases PLT aggregability. On the other hand, volume reduction does not adequately remove plasma proteins. Therefore, PLT washing should be reserved for patients with a history of severe allergic or anaphylactic transfusion reactions. We suggest that fresher PLTs be selected to improve the functionality of washed PLTs.