Rh blood group system the clinical consequences of non-recognized "Rh factor", hemolytic transfusion reaction, and hemolytic disease of the newborn in its most severe form. It was recognized that the serum of the reported woman agglutinated with red blood cells of about 80% of the people although the then known blood groups, in particular ABO were matched. No name was given to this agglutinin when described. In 1940, Karl Landsteiner and Alexander S. Wiener made the connection to their earlier discovery, reporting a serum that also reacted with about 85% of different human red blood cells. In 1941, Group O: a patient of Dr.
Blood type and removed from solution. In addition to the current practice of serologic testing of blood types, the progress in molecular diagnostics allows the increasing use of blood group genotyping. In contrast to serologic tests reporting a direct blood type phenotype, genotyping allows the prediction of a phenotype based on the knowledge of the molecular basis of the currently known antigens. This allows a more detailed determination of the blood type and therefore a better match for transfusion, which can be crucial in particular for patients with needs for many transfusions to prevent allo-immunization. Blood types were first discovered by an