Classification of blood groups should be based on both forward and reverse grouping. ABO blood group system is determined by the direct reaction of erythrocytes with Anti-A and Anti-B reagents. Confirmation of test results is provided by testing known group A1 and group B erythrocytes and serum. The OBG Forward and Reverse Grouping test enables the detection of ABO, Rh D, Rh D VI and reverse grouping.