Acute Hemolysis in a Patient with Anti-U Despite a Negative MMA Test

Obtaining compatible units for patients with alloantibodies to high frequency antigens poses an extreme challenge for transfusion specialists because these rare units are expensive, in high demand, and are often needed emergently. However, because not all antibodies are clinically significant, the monocyte monolayer assay (MMA) is sometimes utilized to predict patient in vivo reactivity to more readily available, antigen positive units. Negative MMA results suggest that antigen-positive units may be incapable of inciting a hemolytic response and can therefore be utilized in lieu of rare, more expensive antigen-negative units. We describe a patient with anti-U antibodies who, despite a negative MMA result, subsequently developed an acute hemolytic transfusion reaction when challenged with U positive blood. Transfusion, management and follow-up of such patients are also discussed. [PUBLICATION ABSTRACT]