ABO testing is a two-part process, involving testing a person’s red cells for A and/or B antigens as well as testing the person’s serum/plasma for ABO antibodies. Testing the cells is called “red cell grouping,” but most use the term “forward grouping” interchangeably (and, when we feel like using jargon that only other blood bankers understand, we may say “front type”). In red cell/forward grouping, red blood cells are mixed with powerful manufacturer-supplied anti-A and anti-B, and evaluated for reaction. Interpretation of the cell group is pretty easy (anti-A+/anti-B– = Group A, etc.), but the result must be correlated with the interpretation of the serum grouping to ensure that both point to the same ABO group. If not, by definition, there is an ABO discrepancy that must be investigated.