HLA and RBC immunization after filtered and buffy coat-depleted blood transfusion in cardiac surgery: a randomized controlled trial

BACKGROUND: WBC reduction of all blood components is being introduced in many countries. Prevention of immunologic side effects of transfusions is part of the motivation. To compare the immunogenicity of before- or after-storage WBC-reduced RBCs with RBCs without buffy coat, a randomized clinical trial was performed. STUDY DESIGN AND METHODS: Cardiac surgery patients were randomly assigned to receive either RBCs without buffy coat (PCs), WBC-reduced RBCs that were filtered before storage (FFs), or WBC-reduced RBCs that were filtered after storage (SFs). Serum samples for antibody analyses were collected before and after surgery. RESULTS: Sera of 404 patients were tested. Of the 317 patients with negative preoperative screening, 12.6 percent developed anti-WBC antibodies (PC, 14.5%; FF, 9.6%; SF, 13.3%). Of the 87 patients with preoperative anti-WBC antibodies, 28.7 percent showed a marked increase in panel reactivity (PC, 31.3%; FF, 29.0%; SF, 25.0%). ELISA showed the newly formed antibodies to be of IgG class and directed against HLA class I in more than 90 percent of the samples tested. Newly formed anti-RBC antibodies appeared in 5.3 percent (PC, 7.1%; FF, 3.4%; SF 5.4%). Alloimmunization against WBCs and RBCs was strongly correlated (p < 0.01). The differences in newly formed anti-WBC antibodies and anti-RBC antibodies between the trial arms did not show significance. CONCLUSION: Buffy coat removal, and additional WBC reduction by filtration, either before or after storage, result in similar posttransfusion alloimmunization frequencies after a single transfusion event with multiple RBCs.