Transfusion Efficacy of Apheresis Platelet Concentrates (APCs) Irradiated in Advance Is Significantly Lower Compared to Products Irradiated within 24 hours Before Transfusion.

Several guidelines on gamma irradiation of blood components state that platelets can be irradiated at any stage in their five-day storage and can thereafter be stored up to their normal shelf life of five days after collection. We explored whether the timing of irradiation has an effect on the transfusion efficacy of APCs.

Transfusion efficacy of 809 APCs (median 6/child; range 1-68) transfused to 113 children and adolescents (53 girls and 60 boys, age 0.1y-20.0y) with thrombocytopenia due to a reduced platelet production caused by their haematological/oncological disease itself or by the applied chemotherapy was evaluated retrospectively. Transfusions were divided according to 3 APCs-groups: nonirradiated, irradiated within 24 hours before transfusion (≤ 24h), and irradiated in advance (> 24h). Exclusion criteria were: splenomegaly, fever ≥38.5°C, hemorrhage ≥ WHO Grade 3, or discontinuation of transfusion due to transfusion reactions. Transfusion efficacy was measured by the 1-hour PPR, ( PPR_1h [%] = (post-transfusion count [10⁹/L] – pre-transfusion count [10⁹/L]) x blood volume [L] / PLT dose [10¹¹/L]). Accounting for the many patients receiving multiple transfusions, linear mixed regression was used for univariate and multivariate analyses.

Univariate comparison of PPR_1h is summarized in the table.

We recently have shown that a variety of factors influences transfusion efficacy of APCs (TRANSFUSION 48; 2008, p.442; TRANSFUSION 49; 2009, p.21). Therefore, all these variables were included in the present analysis. Multivariate analysis, corrected for storage time, applied apheresis procedure, apheresis yield, ABO transfusion constellation, body weight of recipients, and platelet count before transfusion, confirmed that transfusion of APCs irradiated in advance was associated with a significantly inferior transfusion efficacy compared to nonirradiated APCs (estimated difference in PPR_1h, 4.9%; 95% confidence interval, 1.3 to 8.5; p=0.008), while transfusion efficacy of APCs irradiated within 24 hours before transfusion was not (estimated difference in PPR_1h, 2.3%; 95% confidence interval, -1.0 to 5.5; p=0.18).

Interestingly, no significant difference in transfusion efficacy could be observed between nonirradiated and APCs irradiated within 24 hours before transfusion, while transfusions of platelets irradiated in advance were significantly less efficient. Although many studies, including our own, provide evidence that gamma irradiated platelets have a lower transfusion efficacy, there are no data exploring the impact of the timing of the irradiation. Although our retrospective study indicates a reduced transfusion efficacy of APCs irradiated in advance, only a prospective randomized trial can unequivocally answer the question when platelets should be irradiated.

Our data strongly support that irradiation of APCs should be performed at the latest within 24 hours before transfusion. APCs irradiated in advance are less efficient.

No relevant conflicts of interest to declare.