A hemolytic reaction implicating Sda antibody missed by immediate spin crossmatch

Anti-Sda, an antibody not usually considered to cause of hemolytic transfusion reactions, possibly was related to hemolysis following transfusion of red blood cells expressing strong Sda antigen. Prior to transfusion, the antiglobulin antibody screen performed in LISS and an immediate spin crossmatch were negative. Retrospectively, after hemolysis was detected, an antiglobulin crossmatch with red cells from the transfused unit revealed microscopic incompatibility. The transfused unit proved to have strong expression of Sda antigen-facilitating identification of a weak Sda antibody in our patient. In addition, this case represents an unusual instance in which an antibody screen plus an immediate spin crossmatch failed to detect an incompatibility that would have been apparent had an antiglobulin crossmatch been performed.