Why are platelets irradiated?

From the Guidelines

Platelets are irradiated to prevent transfusion-associated graft-versus-host disease (TA-GVHD), a rare but usually fatal complication of transfusion of blood components.

Reasons for Irradiation

• TA-GVHD is caused by the transfusion of viable lymphocytes capable of immune attack against the recipient 1
• Irradiation of blood products with a minimal dose of 25 Gy is recommended to prevent TA-GVHD, particularly for patients at greatest risk, including recipients of autologous and allogeneic stem-cell transplants, those receiving blood products from partially matched family members, and patients with severe immunosuppression 1
• Leukocyte depletion by itself does not eliminate the possible occurrence of TA-GVHD, making irradiation necessary 1

Methods of Irradiation

• Gamma irradiation is currently the standard method for preventing TA-GVHD 1
• UV irradiation pathogen inactivation techniques are being developed and may potentially eliminate the need for irradiation of platelet products in the future 1

Clinical Practice

• Clinicians should be aware of the irradiation policies of their local blood suppliers and communicate with them about patients for whom irradiated products are appropriate 1
• Some cancer centers have chosen to irradiate blood products routinely for all patients to guarantee that more vulnerable recipients receive the proper products 1

From the Research

Purpose of Platelet Irradiation

• Platelets are irradiated to prevent transfusion-associated graft-versus-host disease (TA-GvHD) as well as transfusion-transmitted infections 2
• Irradiation of platelet products is required in patients who may develop TA-GVHD 2, 3

Effects of Irradiation on Platelets

• Gamma irradiation has no significant effect on the quality of platelet products, but may lead to the induction of platelet storage lesion (PSL) and reduce the efficiency of transfused platelets 2
• UV-illumination can prevent TA-GvHD, but may also induce oxidative conditions and platelet pre-activation, leading to PSL 2
• X-ray irradiation has been shown to have similar effects on the in vitro quality of platelet components as gamma irradiation 3, 4

Studies on Irradiation Techniques

• A study in 1986 found that 5000 rad of gamma irradiation did not alter platelet morphology, mean platelet volume, or expression of platelet-factor-3 activity 5
• A 2022 study found that gamma and X-ray irradiation did not affect the in vitro quality of refrigerated apheresis platelets in platelet additive solution (PAS-E) 3
• Another 2022 study found that X-irradiated platelet components had equivalent in vitro quality to gamma-irradiated components 4
• A 2003 study found that X-ray radiation increased the Young modulus of elasticity and percent cell activation in platelets, and increased viscosity and activation in lymphocytes 6