Selection of donor RBC units for infants with ABO grouping discrepancies

A Medical Technologist at a Children's hospital in Texas wonders if their current practice of selecting donor RBCs for infant transfusions is 'technically correct'. At her hospital they have a large Neonatal ICU and it is their practice to test infants younger than 4 months for their ABO group and Rh type using commercial antisera, and then to select ABO/Rh identical RBCs for the transfusion of these infants, unless the infant has maternal antibodies in which case they give group O RBCs. When the infant turns 4 months old they repeat the ABO grouping, but this time they test both the patient's red cells with commercial antisera and perform serum (reverse) grouping with A1 and B cells.

Her specific question concerns infants (between 4 months and one year of age) who appear to have ABO results that show discordant cell (forward) and serum (reverse) grouping. She was wondering how much time and effort other hospitals commit to resolving such ABO grouping discrepancies for patients in this age group, and how such patients are managed with regard to donor RBC selection.

Case in point: One baby (who typed as group A Rh positive at birth) was in their Neonatal ICU for approximately the first 2 months of its life, during which time it received group A Rh positive RBCs. The baby was discharged home and readmitted to the hospital at 5 months of age for scheduled surgery. Because the baby was now over 4 months old, its pre-transfusion testing included both forward and reverse ABO tests, which showed the patient's red cells to forward type as group A, but the serum did not react with group A1 or group B reagent red cells. Their current policy is to give such an infant group O Rh positive RBCs until the ABO discrepancy is resolved. They incubated the patient's serum for 30 minutes at room temperature and then at 4 C, but without any reactivity with A1 or B red cells. Thus, the baby has no detectable anti-A nor anti-B in its plasma. Therefore they gave the patient group O Rh positive RBCs, even though for the first two months of its life it had been getting group A Rh positive RBCs. How would others have approached this situation?

The following comments have been received.

ADDENDA Feb 12, 2005

1. A colleague in Massachusetts reports that based on their experience, they expect patients to develop a valid reverse type by the time they are 9 months old. Before that, they do not necessarily expect a valid reverse type. So, using the example described by the inquiring colleague, if they had a patient between 4 months and 9 months old with a forward type of group A RhD postive and no anti-A or anti-B antibodies in the serum, they would consider the patient to be group A Rh positive and transfuse group A Rh positive RBCs. Once the patient becomes at least 9 months old, if they cannot detect anti-A or anti-B despite extended incubations, they would be concerned about the patient's immune status and would investigate the patient's clinical condition.

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