Transfusion of incompatible blood to a patient with alloanti-Sc1

Sc1 is a high-prevalence blood group antigen that is part of the Scianna blood group system. The clinical significance of Scianna antibodies is not well understood because of their rarity; there are only a handful of cases in the literature. This scarcity of information can make it difficult to decide on the best course of action when transfusing a patient with alloantibodies to Scianna blood group antigens. We describe a case of an 85-year-old woman presenting with melena and a hemoglobin of 66 g/L. Upon request for crossmatched blood, a panreactive antibody was found, later elucidated to be alloanti-Sc1. Because of the urgent nature of the transfusion, the patient was transfused with 2 incompatible, presumed Sc1+, red blood cell units with no evidence of an acute or delayed transfusion reaction. This case has been shared with the International Society of Blood Transfusion Rare Donor Working Party, via their Outcome of Incompatible Transfusion form, and adds to the body of evidence on clinical significance of antibodies to the antigens of the Scianna blood group system.