Prevention - Transfusion-Associated Graft-vs- Host Disease (TA-GVHD)

Currently the only method of preventing transfusion-associated graft versus host disease (TA-GVHD) is to gamma irradiate cellular components at risk of causing TA-GVHD or destined for at risk recipients. Current techniques to leukoreduce cellular blood components are not adequate to prevent TA-GVHD

• Irradiated blood is prepared by exposing the component to a source of gamma irradiation. To eliminate the proliferative capacity of leukocytes, the central midplane of the canister should receive 2500 cGy and the lowest dose delivered to any portion of the canister should be 1500 cGy.

Canadian Blood Services produces the following gamma irradiated products:

• Red Blood Cell products, LR
• Platelets, LR
• Platelets Apheresis, LR

Gamma irradiation, in the doses recommended for the prevention of TA-GVHD, does not affect the function of platelets. However, it does result in some damage to the erythrocyte membrane so that the permitted storage date of red cell concentrates is 28 days following irradiation (or the usual expiry date, whichever is shorter). There is also a more rapid accumulation of potassium in the extracellular fluid of the red cell concentrates. For this reason, for neonates and young children, it is preferable to gamma irradiate red cell components as close to the time of transfusion as possible. In these patients, if the units have not been irradiated just prior to transfusion, removal of extracellular fluid, (to reduce risks associated with high plasma potassium), may be considered.