Optimized strategy to mitigate daratumumab interference in blood bank testing: Reducing cost and time.

Objective: Drug interference with pretransfusion testing in patients with multiple myeloma (MM) treated with daratumumab (DARA) is well recognized. Current guidelines recommend that these patients should have a red blood cell (RBC) phenotype or genotype before DARA initiation; however, there are no other standards for pretransfusion testing. While prior publications report mitigation strategies and low RBC alloimmunization risk, they do not propose a cost-effective strategy for pretransfusion testing. This study aims to assess the RBC alloimmunization risk in patients treated with DARA and propose a cost-effective algorithm for pretransfusion testing.

Methods: This is a retrospective study of patients treated with DARA and receiving RBC transfusions over 9.4 years (October 1, 2015, to January 30, 2025). Demographic data; a complete serologic profile, including blood typing, antibody screen (Ab screen), and antibody identification (Ab ID); RBC phenotype/genotype; and crossmatch data were collected for each patient. The clinically significant antibody formation incidence was recorded pre- and post-DARA and compared with a control group, with statistical significance defined as P < .05. The mitigation strategy initially used for pretransfusion testing and its optimized version are described along with their cost.

Results: Of the 850 patients with MM on DARA therapy who were identified, 172 (20%) received at least 1 RBC transfusion. Ab screens were performed on all patients pre- and post-DARA therapy. Following drug administration, all patients showed a panagglutinin, and no patients formed new clinically significant alloantibodies. The turnaround time (TAT) and cost significantly decreased when the pretransfusion strategy with optimizing pretransfusion strategy.

Conclusions: This is the most extensive study on patients treated with DARA and transfused, demonstrating no increased alloimmunization risk. DARA-related transfusion interference may be successfully mitigated by the novel strategy proposed here.