What is the Incidence of Early Antibody Formation After Resuscitation of Hemorrhage? A Comparison of RH(D)+ Whole Blood and RH(D)− Red Blood Cells in 3531 Trauma Patients

OBJECTIVE: To evaluate the risk of red blood cell alloimmunization following transfusion of low-titer group O whole blood (LTOWB) compared with component therapy in severely injured trauma patients. SUMMARY BACKGROUND DATA: LTOWB is increasingly used for trauma resuscitation because of logistical advantages and potential hemostatic benefits. However, concerns remain regarding alloimmunization, particularly anti-D antibody formation in Rh(D)-negative patients exposed to Rh(D)-positive blood products. METHODS: A retrospective cohort study was conducted at a single Level I trauma center using trauma registry data from 2017 to 2023. Adult trauma patients (15 y or older) who received emergency release uncrossed blood products prehospital or shortly after admission were included. Patients were categorized by exposure to Rh(D)-positive LTOWB (WB group) or Rh(D)-negative component therapy alone (COMP group). Antibody screening was performed on admission and repeated at 72-hour intervals during hospitalization. The primary outcome was the incidence of alloimmunization. RESULTS: A total of 3531 patients met the inclusion criteria, including 2103 in the WB group and 1428 in the COMP group. Post-transfusion alloantibody formation occurred in 3% of WB patients (n=63) and 2% of COMP patients (n=32). Among WB patients who developed alloantibodies, anti-D antibodies accounted for 11% of detected antibodies, with anti-E most common (22%). In the COMP cohort, anti-D antibodies accounted for 20% of the detected antibodies. In both groups, alloantibody formation was more common in Rh(D)-negative patients. CONCLUSIONS: LTOWB transfusion in severely injured trauma patients was associated with a low incidence of alloantibody formation comparable to component therapy, supporting the immunohematological safety of LTOWB in trauma resuscitation.