Background and Introduction to the ABO System
Table 3: Testing the Serum with Known Red Cells (Reverse Typing)
It has been demonstrated that antibodies occur predictably in the sera of all normal adults in association with the ABO antigens. Demonstration of these antibodies is therefore necessary for definitive classification of an individual’s ABO cell type. The individual’s serum is therefore tested against reagent red cells containing known antigens.
| A | 0 | 4+ |
| B | 4+ | 0 |
| O | 4+ | 4+ |
| AB | 0 | 0 |
