[1,3] Antibodies to Kell blood group system are the most common immune red- cell system following ABO and Rh systems but anti-Kpa antibody is extremely rare. Antibodies that target Kell antigens can cause transfusion reactions and hemolytic disease of the newborn (HDN). Kpa antigen is a low incidence red blood cell antigen within the Kell system. Agglutination indicates the presence of the Kpa antigen on the red blood cells and is interpreted as a positive result. Anti-Kpa is an antibody directed to an antigen of the Kell blood group system. hydropic HDFN due to anti-Kpa antibodies discovered incidentally with direct antiglobulin testing of a fetal blood sample in the course of.