How do transfusion services manage patients taking therapies such as anti-CD38 and anti-CD47 known to interfere with red blood cell compatibility testing?

Background: Drugs such as daratumumab (Darzalex, anti-CD38) and Hu5F9-G4 (magrolimab, anti-CD47) may interfere with red blood cell compatibility testing as CD38 and CD47 are expressed on red blood cells. Study Design and Methods: A survey of AABB member transfusion services was undertaken to understand their experiences of managing patients taking therapeutic monoclonal antibodies that are known to interfere with blood grouping and compatibility testing. Results: The survey was distributed to the contact person at US-based AABB member transfusion services. The response rate was 27%. 172 of 240 (72%) indicated they had difficulties in performing compatibility testing in patients taking daratumumab and 66 of 91 (73%) reported difficulties in performing compatibility testing in patients taking magrolimab. Actions taken to provide compatible blood for these patients included referral of all samples to a reference center, blood group pheno/genotyping the patient in advance of starting the drug, treating reagent cells with 0.2 M dithiothreitol and using K-negative red cell units for patients taking daratumumab, and Gamma-clone (Immucor) anti-IgG for indirect antiglobulin testing for patients taking magrolimab. Lack of communication from clinical services about drug treatment was identified as a concern. Conclusion: The results of the survey demonstrate that transfusion services are having challenges with the transfusion management of patients taking therapeutic monoclonal antibodies, and further education is needed.