Comparison of X-ray vs. gamma irradiation of CPDA-1 red cells

Background and Objectives Transfusion-associated graft-versus-host disease (TA-GVHD) is a serious, potential complication of blood transfusion that is essentially prevented by blood product irradiation. Blood product irradiation is currently performed using gamma irradiation. X-ray irradiation is an alternative that has certain advantages: an X-ray irradiator is less expensive and does not have a radioactive source. However, the biochemical effects of X-ray irradiation on red blood cells (RBCs) have not been well characterized. The primary purpose of our study was to compare the effects of X-ray irradiation with gamma irradiation on RBC membrane permeability. A secondary purpose was to verify that X-ray irradiation has the same effect on lymphocytes as gamma irradiation. Materials and Methods Ten RBC units were split into two portions; five units of each were then irradiated with either gamma or X-ray at a dose of 35 Gy or 25 Gy, respectively. Free plasma haemoglobin and extracellular potassium levels were measured in each unit over time. Another unit was divided into three parts for lymphocyte studies; one part was not irradiated as a control and the other two received 25 Gy of irradiation via X-ray or gamma irradiation, respectively. Results Minimally increased free plasma haemoglobin was found only in X-ray-irradiated units after 25 Gy compared to gamma-irradiated units. However, extracellular potassium levels were not significantly different in these groups. Extracellular potassium levels were slightly higher only in gamma irradiated units at 35 Gy. X-ray and gamma irradiation were equivalent in affecting lymphocyte function. Conclusions Small differences in RBC membrane permeability are found between gamma-irradiated and X-ray-irradiated units. However, these differences are not likely to be clinically important.