How did DAT happen? A Coombs Negative Delayed Hemolytic Transfusion Reaction in a Patient with Myelodysplastic Syndrome: A Case Report

Delayed hemolytic transfusion reactions (DHTRs) present significant challenges in diagnosis and management despite advancements in pre-transfusion testing. We report a case of a 76-year-old female with myelodysplastic syndrome (MDS) who developed severe hemolytic anemia following a seemingly compatible blood transfusion and appropriate pretransfusion testing. Evaluation revealed characteristics consistent with DHTR. Diagnostic uncertainty arose due to a negative Direct Antiglobulin Test (DAT) in the setting of a concomitant Vitamin B-12 deficiency. She was supported with prednisone and B12 supplementation. We discuss challenges in diagnosis, including the limitation of DAT, and propose strategies for comprehensive antibody identification. The case underscores the importance of recognizing DHTR and the phenomenon of antibody evanescence, highlighting the need for a national transfusion registry to enhance patient safety. The case underscores the importance of recognizing DHTR and the phenomenon of antibody evanescence, highlighting the need for a national transfusion registry to enhance patient safety.