Prion filtration tested for red blood cell transfusions

By Lynda Williams, Senior medwireNews Reporter

Red blood cell (RBC) prion filtration does not increase the risk for alloimmunization or transfusion reactions, suggest results from the largest safety study to date.

The trial was conducted by the UK Blood Transfusion Services following concerns that removing prions, a common constituent of plasma, may alter the immunologic profile of RBC plasma membranes and increase the risk for alloimmunization or transfusion reactions.

Patients given a RBC transfusion treated with the P-Capt prion removal filter (Macopharma, Tourcoing, France) did not have a significantly increased risk for the development of anti-RBC antibodies compared with patients given standard transfusions, report Modupe Elebute (King's College Hospital, London) and co-authors.

Overall, 4.2% of patients given filtered blood products developed new antibodies compared with 4.5% of controls, and none of the patients developed pan-reactive antibodies or antibodies specifically against prion-filtered red cell concentrates.

The alloimmunization rate was not significantly influenced by the number of RBC transfusions the patients received. Nor did the rate of transfusion reactions or adverse events significantly differ between the treatment groups.

The study included 299 patients given 917 U of prion-filtered RBCs and 291 patients given 1336 U of standard RBC transfusions. The patients were followed up 8 weeks after transfusion and again after 6 months.

The researchers explain that collection of follow-up blood samples was logistically challenging as the study was based on elective cardiac surgery patients who were largely frail and elderly, and living a significant distance from their surgical hospital.

"Despite these limitations, the study team managed to collect at least one post-transfusion blood sample in almost 80% of patients," the authors say.

Nevertheless, they explain that "whether repeated transfusion of this product to transfusion-dependent patients would result in increased alloimmunization rates has not been addressed in this study."

Elebute et al therefore conclude: "Our findings suggest that transfusion of red cells filtered through the P-Capt™ filter does not appear to reduce the overall safety of transfusion.

"These data require to be confirmed in larger patient populations, and in the multi-transfused, either by further trials or, more feasibly, through post-marketing surveillance."

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