In a massive transfusion setting, the patient’s forward and reverse type will reflect the use of group O RBCs and the patient may even fully type as group O, depending on the number of units transfused.  Group O RBCs are very precious and in short supply so we need to switch the patient back to his/her own type as soon as feasible.  RBCs in additive solution (e.g. SAGM) have only minimal residual plasma so the load of anti-A,B from the O cells is minimal.  In my organization, we did not titer ABO hemolysins in blood donors.

Here is my approach:

1. Use fresh specimen to perform forward and reverse type
2. Check the reverse type:  does it show either anti-A and/or anti-B from the group O massive transfusion?
   1. If anti-A detected, do not give group A RBCs.
   2. If anti-B detected, do not give group B RBCs.
   3. If both anti-A and anti-B detected, continue using only group O RBCs.

Some people would recommend performing a full AHG crossmatch using the patient’s current plasma and RBCs of the original ABO type:

1. If compatible, return to the original ABO type.
2. Otherwise, continue using group O RBCs.

I did NOT do the full AHG crossmatch and had no hemolytic transfusion reactions if the RBCs were compatible with the current reverse type plasma.